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GHENT UNIVERSITY
FACULTY OF VETERINARY MEDICINE
Academic year 2010-2011
The copper soil-plant-animal cycle: factors associated with copper status of cattle in the
Gilgel Gibe Catchment, Ethiopia
By
Thomas VAN HECKE
Promoter: V. Dermauw Research Project in the context
Co-promoters: Prof. Dr. Ir. G. Janssens of the Master Thesis
Y. Kechero
2
The author and the promoters agree this thesis is to be available for consultation and for personal
reference use. Every other use falls within the constraints of the copyright, particularly concerning the
obligation to specially mention the source when citing the results of this thesis.
The copyright concerning the information given in this thesis lies with the promoters. The copyright is
restricted to the method by which the subject investigated is approached and presented. The author
herewith respects the original copyright of the books and papers quoted, including their pertaining
documentation such as tables and illustrations. The author and the promoters are not responsible for
any recommended treatments or doses cited and described in this study.
May 2011, Merelbeke
3
Acknowledgments
This dissertation was made possible by the efforts of many people who offered their support and
expertise. First of all, I would like to express my deepest gratitude to my promoter Prof. Dr. Ir. Geert
Janssens for giving me the chance of performing veterinarian research in Africa. Without his guidance,
suggestions and financial support, this project would not be possible. I would also like to thank
Veronique Dermauw who was always willing to advise and help when problems arose during
fieldwork. Her patience, corrections and suggestions contributed largely to the successful completion
of this thesis. Great appreciations go to Yisehak Kechero for his invaluable plant expertise and
company in the field. I am grateful to Prof. Dr. Eric Van Ranst for taking the time to explain me the
difference in soil types in the Gilgel Gibe Catchment. Also Dr. Moti Yohannes was greatly appreciated
for his help and assistance in the parasitology lab at JUCAVM (Jimma University College of
Agriculture and Veterinary Medicine).
I would like to express my gratitude to the workers in the Jimma Municipal Abattoir for their
cooperation. Fieldwork was not possible without the assistance of several community workers and
drivers and of course the cooperation of local farmers.
Last but not least, I would also like to thank all the other Belgian thesis students at JUCAVM and
Ethiopian students, Brooke Kebede and Shemita Misganaw in particular, for their companionship and
friendship. They made this research not only a unique scientific but also an unforgettable life
experience.
Thomas Van Hecke
4
Table of Contents
Abstract ................................................................................................................................................ - 1 -
Introduction .......................................................................................................................................... - 2 -
PART 1: Literature Survey ................................................................................................................ - 3 -
1.1 Copper ........................................................................................................................................... - 4 - 1.1.1 Function of copper in cattle .................................................................................................... - 4 - 1.1.2 Copper metabolism ................................................................................................................ - 4 - 1.1.3 Deficiency symptoms .............................................................................................................. - 5 - 1.1.4 Diagnosis of copper deficiency ............................................................................................... - 7 -
1.2 Copper deficiency in the East of Africa .......................................................................................... - 8 - 1.2.1 The Rift Valley ........................................................................................................................ - 8 - 1.2.2 Ethiopia .................................................................................................................................- 10 - 1.2.3 Jimma ...................................................................................................................................- 12 -
1.3 The copper cycle in the soil – plant – cattle system ....................................................................- 12 - 1.3.1 Summary scheme .................................................................................................................- 12 - 1.3.2 Parent material .....................................................................................................................- 13 - 1.3.3 Soil ........................................................................................................................................- 14 -
1.3.3.1 Association soil pH and bioavailability molybdenum and copper .................................- 14 - 1.3.3.2 Soil types around Jimma ...............................................................................................- 14 - 1.3.3.3 Influence of altitude on mineral concentrations in nitisols .............................................- 15 - 1.3.3.4 Influence of altitude on mineral concentrations in plants ..............................................- 15 - 1.3.3.5 Influence of altitude on mineral concentrations in cattle ...............................................- 15 -
1.3.4 Plants ....................................................................................................................................- 16 - 1.3.4.1 General..........................................................................................................................- 16 - 1.3.4.2 Copper antagonists .......................................................................................................- 16 - 1.3.4.3 Tannins..........................................................................................................................- 16 - 1.3.4.4 Season ..........................................................................................................................- 16 -
1.3.5 Cattle ....................................................................................................................................- 17 - 1.3.5.1 Fysiological status .........................................................................................................- 17 - 1.3.5.2 Infection .........................................................................................................................- 17 - 1.3.5.3 Parasites .......................................................................................................................- 17 - 1.3.5.4 Geophagy ......................................................................................................................- 18 -
PART 2: Materials and Methods .....................................................................................................- 19 -
2.1 Prevalence of copper deficiency ..................................................................................................- 20 -
2.2 Evaluation of management practices ...........................................................................................- 20 - 2.2.1 Study area ............................................................................................................................- 20 - 2.2.2 Soil and geophagy ................................................................................................................- 21 - 2.2.3 Management practice ...........................................................................................................- 22 - 2.2.4 Plant intake ...........................................................................................................................- 22 - 2.2.5 Blood sampling .....................................................................................................................- 23 - 2.2.6 Statistical analysis ................................................................................................................- 23 -
5
PART 3: Results ...............................................................................................................................- 24 -
3.1 Prevalence of copper deficiency ..................................................................................................- 25 -
3.2 Management practices.................................................................................................................- 27 - 3.2.1 General .................................................................................................................................- 27 - 3.2.2 Background information........................................................................................................- 28 - 3.2.3 Statistical analysis ................................................................................................................- 29 -
3.3 Plant composition of the diet ........................................................................................................- 30 - 3.3.1 General .................................................................................................................................- 30 - 3.3.2 Background information........................................................................................................- 32 -
3.3.2.1 Diet composition according to region ............................................................................- 32 - 3.3.2.2 Diets in Planosols/Vertisols ...........................................................................................- 32 - 3.3.2.3 Diets in Nitisols/Ferralsols .............................................................................................- 32 -
3.3.3 Statistical analysis ................................................................................................................- 32 -
3.4 Mineral composition of plant species ...........................................................................................- 33 - 3.4.1 General .................................................................................................................................- 33 - 3.4.2 Mineral composition plants according to region ...................................................................- 33 - 3.4.3 Mineral composition plants according to soil type ................................................................- 33 -
3.5 Mineral intake in selected cattle ...................................................................................................- 34 - 3.5.1 General .................................................................................................................................- 34 - 3.5.2 Statistical analysis ................................................................................................................- 35 -
3.5.2.1 Mineral intake in cattle according to region ...................................................................- 35 - 3.5.2.2 Mineral intake in cattle according to soil type ...............................................................- 35 - 3.5.2.3 Mineral intake in cattle according to feeding strategy ...................................................- 35 -
3.6 Mineral concentrations in plasma of selected cattle ....................................................................- 36 - 3.6.1 General .................................................................................................................................- 36 - 3.6.2 Statistical analysis ................................................................................................................- 37 -
3.6.2.1 Influence of management on mineral concentrations in plasma...................................- 37 - 3.6.2.2 Correlation between mineral content in diet and plasma ..............................................- 38 -
PART 4: Discussion .........................................................................................................................- 40 -
4.1 Prevalence of copper deficiency ..................................................................................................- 41 -
4.2 Management Practices ................................................................................................................- 41 -
4.3 The copper cycle in the soil-plant-cattle system ..........................................................................- 42 - 4.3.1 Summary scheme results .....................................................................................................- 42 - 4.3.2 The influence of soil-type on mineral concentrations in plants.............................................- 43 - 4.3.3 Mineral content of forages in the Gilgel Gibe Catchment .....................................................- 44 - 4.3.4 The influence of diet on mineral status of cattle ...................................................................- 46 -
4.3.4.1 Botanical composition ...................................................................................................- 46 - 4.3.4.2 Mineral composition ......................................................................................................- 46 -
4.3.5 The influence of soil-type on mineral concentrations in cattle..............................................- 47 -
4.4 Suggestions to improve copper status .........................................................................................- 48 -
PART 5: Addendum and References .............................................................................................- 49 -
5.1 Addendum ....................................................................................................................................- 50 -
5.2 References ...................................................................................................................................- 54 -
Abstract
In tropical and subtropical countries mineral deficiency, unbalance and toxicity are frequently
observed in grazing ruminants. Ethiopia is a landlocked country located in the Horn of Africa
and the country’s estimated cattle population of about 45 million in 2007 is believed to be
Africa’s largest (FAO, 2007). A study conducted by Dermauw et al. (2009) in the Gilgel Gibe
valley in SW Ethiopia proved altitude as an influencing factor on the mineral status of cattle.
This research was conducted in the same valley to evaluate the impact of different
management practices on the copper status of cattle and to improve the productivity and
reproduction of grazing cattle. Also estimation has been made on the prevalence of copper
deficiency in the region. From the 53 liver samples collected at Jimma municipal abattoir, 81%
had deficient copper levels, from which 58% were in the clinically deficient range.
The practice of communal- or individual herding and herd size did not influence copper status
in cattle. The botanical and mineral composition of diets was determined for 19 cattle. 87
different plant species belonging to 25 plant families were ingested and 52 different plant
species were analysed for mineral content. Analysis of plant species showed mineral
imbalances as a widespread phenomenon in the Gilgel Gibe Catchment. Cattle grazing on
planosols/vertisols and associated wetlands ingested significantly lower amounts of copper
and higher amounts of molybdenum than cattle grazing on nitisols/ferralsols. Higher
molybdenum concentrations in diet were significantly associated with lower copper status in
cattle. Also cattle grazing in the wetlands had lower copper status than cattle grazing in well
drained lands. These results indicate cattle grazing on wetlands are more likely to develop
severe copper deficiency than cattle grazing on well drained soils.
- 2 -
Introduction
Ethiopia is a landlocked country located in the Horn of Africa and with over 80.7 million people it is the
second most populous nation in Africa. The country’s estimated cattle population of about 45 million in
2007 is believed to be Africa’s largest. Ethiopia is ranked number six on the list of highest numbers of
cattle in the world (FAO, 2007). The livestock sector contributes about 30% of agricultural GDP and
12% of total GDP excluding the value of draught power and manure. About 10 million oxen work as
draught animals in agricultural areas. Export of livestock counts for 14% of agricultural export and 11%
of total export. Hereby, the livestock sector is the second most important export product next to coffee.
Live animals are exported to Somalia for re-export to the Gulf countries and Yemen, but also to
Kenya, Sudan and Eritrea (GRM, 2007). Cattle production is distributed throughout the country with
the greatest concentration in the highlands.
Cattle in Ethiopia are almost entirely of the zebu type and are poor sources of milk and meat.
However, these cattle do relatively well under the traditional production system. Contagious diseases
and parasitic infections are major causes of death. Recurring drought takes a heavy toll on the animal
population, although it is difficult to determine the extent of losses. During the rainy seasons water and
grass are generally abundant but with the onset of the dry season forage is generally insufficient to
keep animals nourished and able to resist disease (Ofcansky and LaVerle, 1991).
In tropical and subtropical countries mineral deficiency, unbalance and toxicity are frequently observed
in grazing ruminants. Phosphorus is most likely to be deficient, followed by copper, cobalt, sodium,
iodine and selenium. Intoxication of selenium, molybdenum and fluorine are also widespread in
tropical countries. Furthermore, numerous reports are available about deficiencies and toxicities of
other minerals, such as calcium, magnesium, potassium, iron, zinc and manganese (McDowell et al.,
1983). The losses in production caused by clinical and subclinical shortage of minerals in livestock are
enormous (Thornton et al., 1972a, 1972b). Marginal deficiencies are more widespread than severe
shortages and affect large number of animals in tropical countries. Because marginal shortage is
associated with a reduction of productivity, growth rate and reproduction it is very important to detect
these deficiencies in cattle (Underwood, 1981).
Faye et al. (1986) performed a survey on the mineral status of ruminants in Ethiopia. Analysis of
plasma samples showed severe and marginal shortage of copper was widespread. Remarkably, all
severe deficiencies and a minority of the marginal shortages were prevalent in the Rift Valley.
A study conducted by Dermauw et al. (2009) in the Gilgel Gibe valley proved altitude as an influencing
factor on the mineral status of cattle. Cattle grazing in lower altitudes seemed to have a lower copper
status than cattle grazing in higher altitudes. Since there were significant differences in copper status
between different herds at the same altitude, the study concluded that there must be other factors
influencing copper status.
This research was conducted in the same valley to evaluate the impact of different management
practices on mineral status of cattle and to improve the productivity and reproduction of grazing cattle.
- 4 -
1.1 Copper
1.1.1 Function of copper in cattle
Copper is an essential trace element that is incorporated in a various amount of metallo-enzymes.
Shortage of copper leads to impaired function of these enzymes and results in several symptoms. A
summary of the most important copper enzymes and their functions and deficiency symptoms is given
by Table 1.
Table 1: physiological functions and deficiency symptoms of the most important copper
dependant enzymes (from McDowell, 2003; Underwood and Suttle, 1999)
Enzymes Physiological functions Deficiency symptoms
Cytochrome oxidase Terminal oxidase in the respiratory chain
Lysyl oxidas Adds a hydroxyl group to lysine residues
in collagen, allowing cross-linking between collagen fibres
Impaired wound healing and blood vessel integrity
Cu-Zn superoxide dismutase E.g., protection of erythrocytes against oxygen radicals Anaemia
Ceruloplasmin (Ferroxidase I) Ferroxidase II
Important in the flow of iron that supports hematopoiesis Anaemia
Dopamine-β-hydroxylase Dopamine-β-mono-oxygenase Hydroxylation of dopamine
Tyrosinase Melanin formation Lack of pigmentation (achromotrichia)
Superoxide dismutases Extracellular ceruloplasmin Intracellular Cu thioneins
Antioxidant defence
1.1.2 Copper metabolism
Monogastric and pre-ruminant animals absorb copper more efficiently than ruminants. High amounts
of copper released during rumen digestion are likely to be precipitated as copper sulphide (Underwood
and Suttle, 1999). When high amounts of molybdenum and sulfur are present in diet, thiomolybdates
are formed in the rumen, which reduce copper absorbability. Consequently, excess of molybdenum
and sulphur in diet have a negative influence on copper status (Underwood and Suttle, 1999;
McDowell, 2003). Increased dietary concentrations of iron and zinc can also have an inhibitory effect
on the utilisation of copper (Van Campen and Scaife, 1967; Hall et al., 1979; Humphries et al., 1983).
Table 2 shows ideal concentrations of minerals in forages. Values outside normal concentrations are
classified into either a marginal or high antagonistic likelihood. Maximum Tolerable Classification
(MTC) is defined as the maximum dietary level that will not impair animal performance when fed for a
limited period (Mortimer et al., 1999).
- 5 -
Table 2: classification of trace elements in forage relative to their abilities to meet either dietary
requirements (A) or cause an antagonistic problem with copper (B) (Mortimer et al., 1999)
A. Trace mineral Severely deficient
Marginally deficient Adequate MTC
Copper (mg/kg) < 4 4 - 9,9 > 10 100 Manganese (mg/kg) < 20 20 - 39,9 > 40 1000 Zinc (mg/kg) < 20 20 - 29,9 > 30 500 Selenium (µg/kg) < 100 100 - 199,9 > 200 2000 Copper:Mo Ratio < 4 4,0 - 4,5 > 4,5 -
B. Copper antagonist Deficient Ideal Marginally antagonistic
Severely antagonistic MTC
Iron (mg/kg) < 50 50-200 200 - 400 > 400 1000,00 Molybdenum (mg/kg) - < 1 1 - 3 > 3 5 Sulfur (%) < 0,10 0,15-0,20 0,20 - 0,30 > 0,30 0,40
MTC= Maximum Tolerable Concentration
Suckling or milk fed animals absorb copper very well with an efficiency of 50% and more. The high
efficiency of copper utilisation and high amounts of copper in the liver of newborn animals, preserve
young animals from the consequences of low copper levels in milk. When a functional rumen
develops, absorbability of copper decreases to 1-10% (Suttle, 1975; Underwood and Suttle, 1999).
Absorption of copper occurs predominantly in the upper section of the small intestine (McDowell,
2003; NRC, 2005). Copper absorbed in the portal blood binds to albumin and transcuprein and is
transported to the liver. Subsequently, copper can be stored in the liver bound to metallothionein,
excreted in bile or used for the synthesis of copper metallo-enzymes. Copper binds to ceruloplasmin
for transportation to extrahepatic tissues. Biliary excretion is the major mechanism for copper
homeostasis (McDowell, 2003; NRC, 2005).
1.1.3 Deficiency symptoms
Depigmentation of hair or achromatrichia is one of the early clinical symptoms of copper shortage in
cattle. Typical is the depigmentation of the hairs around eyes (‘spectacle eye’) and ears (Figure 1A
and 1B), but it can affect all hairs (Figure 1C). Red hairs turn to yellowish-dun (Figure 1A and 1C)
colour while black turns to reddish-brown (Figure 1B). Hair also becomes dull and kinky (Allcroft and
Lewis, 1957; Davis et al., 1946; Harvey, 1952).
A delayed oestrus can be caused by shortage of this mineral and consequently, deficiency can have a
negative influence on fertility and reproduction. Infertility is more likely to be related to secondary
deficiencies due to excess of molybdenum than to primary deficiencies (Kendall et al., 2003). Growth
retardation and delayed puberty in copper deficient calves are also presumably more related to excess
of molybdenum than primary shortage. Cattle supplemented with iron did not alter growth even though
copper plasma levels were depressed (Phillippo et al., 1987a; Phillippo et al., 1987b; Gengelbach et
al., 1994; Underwood and Suttle, 1999). Also the presence of diarrhoea is more attributed to excess of
molybdenum rather than shortage of copper (Ward, 1978).
- 6 -
Figure 1: indications for copper deficiency; A: depigmentation of red hairs around the eyes –
B: depigmentation of black hairs around the eyes and horns – C: severe loss of hair colour
over the whole body, hair looks dull and kinky, diarrhoea on the hindquarters, small posture
Deficiency in copper leads to the dysfunction of ceruloplasmin, a cupro-protein responsible for the
release of iron from the liver. Since iron is a component of haemoglobin, copper shortage leads to an
iron resistant anaemia because of iron accumulation in the liver and to a lesser extent in other organs
such as the spleen (Evans and Abraham, 1973). Iron is next to haemoglobin also a component of
myoglobin, cytochrome and the enzymes catylase and peroxidase. Consequently, iron is responsible
for the transport of oxygen to the cells and cellular respiration.
Ceruloplasmin also acts as an acute phase protein by permitting the incorporation of iron in transferrin.
In this way, free ferrous iron concentrations decrease and thus, ceruloplasmin plays an important role
in anti-oxidant and antibacterial defence (Carver et al., 1982; Letendre and Holbein, 1984).
Copper status influences the non-specific immune function. Shortage of copper leaded to a decreased
ability of granulocytes to kill Candida albicans in sheep and cattle (Jones and Suttle, 1981). Also
depression of neutrophil viability, phagocytic ability and killing capacity were observed as
consequences of copper deficiency. Consequently, copper deficient cattle are more susceptible to
infectious diseases (Boyne and Arthur, 1986; Gengelbach, 1994). No differences were found in total
IgM and IgG between copper deficient and copper adequate calves. Consequently, it seems copper
status does not affect specific immune function (Stabel et al., 1993; Ward et al., 1997).
Copper deficiency can cause malformation of collagen- and elastin fibres (Owen, 1981). These fibres
support lung parenchyma and are necessary for the normal function of the lungs. Malformation of
collagen and elastin in the lungs consequently leads to pulmonary emphysema (O’Dell et al., 1978).
One of the most severe consequences of copper deficiency is loss of integrity and elasticity of arteries
or even the heart. Rupture of major arteries leads to the sudden death syndrome or falling disease
(Allen and Klevay, 1978; Bennetts, 1942).
Copper is essential for normal elastin and collagen production in cartilage, osteoid, ligaments and
tendons. Therefore, lameness and skeletal abnormalities such as osteochondrosis and growth plate
pathologies are also frequently observed due to copper shortage (Maas and Bradford, 1990).
- 7 -
The copper containing enzyme dopamine-β-mono-oxygenase converts dopamine into norepinephrine
(Friedman and Kaufman, 1965). Shortage can lead to disorders of the central nervous system
including ataxia, tremor and clonic seizure. Copper induced ataxia or swayback typically occurs in
newborn lambs (Barlow, 1963).
1.1.4 Diagnosis of copper deficiency
Most clinical signs as described above can also be caused by other factors such as parasitic infections
and Johne’s disease (Herd, 1994). Consequently, copper deficiency can not be diagnosed based only
on clinical symptoms. Determination of copper concentrations in blood plasma and liver lead to the
final diagnosis of copper shortage. Analysis of forage samples for copper, molybdenum, iron and
sulphate and water analysis for sulphate can also help diagnose the problem.
Plasma samples can be used as a general indicator for the copper status of cattle. Plasma copper
concentrations do not reflect dietary intake unless copper storage in the liver is severely depleted
(Underwood and Suttle, 1999). Release of hepatic copper is often sufficient to maintain normal plasma
copper levels until liver copper decreases below 30 mg/kg (Mills, 1987). By the time plasma copper
levels are below normal range, the animal is at least suffering from subclinical deficiency.
Measurement of plasma copper concentration is considered to be the best test available for confirming
cattle with clinical symptoms as deficient (Underwood and Suttle, 1999).
Laven et al. (2007) reported plasma copper concentrations suitable for the detection of marginal
copper status. On the other hand, analysis of serum copper concentrations is not recommended
because the loss of copper during clotting is too great.
Inflammation and infection increase plasma levels of the copper containing ceruloplasmin as part of
the acute phase response (Disilvestro and Marten, 1990; Stable et al., 1993). This increase may
complicate interpretation of plasma copper levels. Ceruloplasmin activity in serum and plasma was
found to be suitable to detect copper shortage in blood (Laven et al., 2007).
When plasma copper concentrations are in the normal range, the only way to determine copper status
is by liver biopsy. Analysis of liver tissue is the best method to evaluate current copper status. In late
pregnancy, plasma and liver copper levels decline drastically in cows (Xin et al., 1993). Values of
copper, iron and zinc in blood and liver are categorised in Table 3.
- 8 -
Table 3: categorisation of copper, iron and zinc levels in blood and liver (adapted from Puls,
1988, Wikse et al., 1992)
Copper Iron Zinc
Status Plasma (mg/l)
Liver DM (mg/kg)
Serum (mg/l)
Liver WM (mg/kg)
Plasma (mg/l)
Liver DM (mg/kg)
Clinically deficient < 0,2 <20 - - - -
Deficient 0,2 - 0,5 <33 0,15 - 1,2 < 40 0,2 - 0,4 < 20 - 40 Marginal 0,5 - 0,7 33 - 125 - - 0,5 - 0,8 25 - 40 Adequate 0,7 - 0,9 125 - 600 1,3 - 2,5 45 - 300 0,8 - 1,4 25 - 200
High 0,9 - 1,1 600 - 1250 4,0 - 6,0 53 - 700 2,0 - 5,0 300 - 600 Toxic > 1,2 > 1250 - - 3,0 - 15,0 > 1000
DM= Dry Matter, WM= Wet Matter
Kellaway et al. (1978) indicated copper levels in hair as a sensitive indicator of copper status when the
copper amount in liver is lower than 20 mg/kg. Hair analysis is not recommended by other authors.
Dirt and contamination lead to overestimation and washing of the hair leads to underestimation of
certain minerals (Herd, 1994).
1.2 Copper deficiency in the East of Africa
1.2.1 The Rift Valley
In the East of Africa different surveys were conducted about the mineral status of cattle and wildlife.
Research in Djibouti, Ethiopia and Kenya has proven that severe copper deficiency is associated with
the pedogeological area of the Rift Valley (Faye en Grillet, 1981; Faye et al., 1986; Faye et al., 1990;
Hedger et al., 1964). The Rift system forms a narrow, elongate fault in the earth’s crust that extends
from Djibouti to Mozambique (Figure 2). The volcanic activity in the Rift has a strong influence on the
present soil types and geochemistry of soil and water. The most important near-surface rock-types are
young, volcanic stones containing either very high or very low levels of certain trace elements (Morley,
1999). Consequently, the volcanic character of the Rift Valley influences the flow of trace elements in
the soil-plant-animal system.
Typical for the Rift are the high concentrations of molybdenum and sulfur in soil and vegetation. Since
these elements are strong antagonists of copper, copper deficiency can still develop in grazing cattle
even when grasses have normal copper values (Faye et al., 1991). Furthermore, other climatic
conditions prevail in the Rift in comparison with the surrounding regions. There is less rainfall in the
Rift en this relative dryness supports dust contamination on plants. Since iron particles are widespread
in African soil types, iron elements can easily land on the vegetation whereby the iron content of plants
is increasing (Faye et al., 1991). Next to molybdenum and sulfur, this mineral is also a strong
antagonist of copper and can induce symptoms of copper shortage (secondary copper deficiency).
- 9 -
Figure 2: illustration of the Rift Valley (adapted from Maps of the World, 2011)
Because of these specific mineral compositions of soil and vegetation and climatic conditions it is not
surprising swayback or enzootic ataxia occurs frequently in the Rift Valley. This nervous disease is
associated with low copper status and is characterized by lack of coordination of movement and
paralysis of the back legs. Swayback is an important problem in newborn ruminants, especially sheep
and goats. Local inhabitants recognise this disease and even have names for it: loïpsiepsiep (Masaï),
kipsiepsiep (Tugen) or degamaka (Afar) (Hedger et al., 1964; Faye et al., 1991; Roeder, 1980b).
The first survey about copper shortage in the Rift Valley was performed around Kenya’s Lakes
Baringo and Harrington in 1964. Through plasma analysis of cattle, sheep and goat widespread
copper shortage was detected in the region. Grazing pastures showed normal copper concentrations
(9.3-12.8 mg/kg) but high molybdenum- (0.5-5.6 mg/kg) and sulfur levels (0.6-6.5%) (Hedger et al.,
1964).
Copper deficiency was also detected in the impala in Lake Nakuru National Park in the Kenyan Rift
Valley. This shortage was caused by low copper status in soil in addition to high molybdenum levels in
grasses. Grazing pastures in the park contained average molybdenum concentration above 2 mg/kg
which was sufficient to induce copper shortage (Maskall and Thornton, 1991).
Similar research was conducted in the Amboseli National Park. This park is also situated in the Rift
close to the Tanzanian border at the foot of the Kilimanjaro. In this area very high molybdenum
concentrations (average of 86 mg/kg) and low copper levels (average of 3.6 mg/kg) were detected in
the grass species Sporobolus spicatus. This species is definitely capable of inducing copper shortage
in cattle and wildlife (Maskall en Thornton, 1996).
In a survey about the nutrition of the sable antelope in the Shimba Hills National Park mineral levels
were also determined in soil and forage samples. This area is situated close to the Kenyan coast and
outside the Rift. Even though soil was poor in copper, grasses had normal copper and molybdenum
levels (Sutton et al., 2002).
- 10 -
Djibouti, a neighbouring country at the Northwest of Ethiopia is largely occupied by the Rift. In 1988 a
survey was conducted on mineral status of cattle in this country. Hundreds of animals (n=310) were
involved and analysis of plasma samples indicated shortage of copper in 17% cattle, 30% goat, 31%
sheep and 46% camels. Furthermore grasses had low copper levels (2.1-5.6 mg/kg) while woody
plants contained higher values (5.4-14.1 mg/kg). In most forage samples concentrations of
molybdenum and sulfur were very high and even reached toxic levels. For example Tamarix nilotica
contained 10.8 mg/kg molybdenum and 1% sulfur (Faye et al., 1990).
Sudan is not crossed by the Rift. Faye et al. (1991) suggested cases of copper deficiency in Sudan
are rare and mild even though soil and vegetation have low copper levels. An explanation is that,
through the nomadic lifestyle of the herders, the animals graze from time to time in copper rich areas,
so they don’t develop shortage. However, several articles report cases of copper deficiency indicating
copper deficiency as a widespread problem in the country (Mukhtar, 1970; Tartour, 1975; Abu Damir
et al., 1983; Abdelrahman et al., 1998).
Furthermore, shortage of copper was detected in forages in the East of Congo (Mandiki et al., 1986)
and Malawi (Mtimuni 1982).
1.2.2 Ethiopia
In 1980, Roeder described for the first time copper shortage in Ethiopia. In 2 isolated locations in the
Rift (Adami Tullu and Metahara) enzootic ataxia was observed in lambs. Plasma copper levels in
ataxic lambs were very low with an average of 0.15 mg/l. Soil contained sufficient available copper but
molybdenum and sulfur concentrations in soil and vegetation were not determined (Roeder, 1980a;
Roeder, 1980b).
During a survey (Faye et al., 1986) on the mineral status of ruminants in Ethiopia 1082 plasma
samples (432 cattle, 425 sheep, 173 goats en 52 camels) from 89 different locations were analysed.
At the same time 59 forage samples from 54 locations were collected. Copper, iron and zinc levels
were determined in the plasma samples. The feed samples were analysed for cobalt, copper, iron,
zinc and manganese. Concentrations of molybdenum and sulfur were not measured.
Analysis of the feed samples indicated shortage of copper and zinc was the most important problem in
mineral nutrition. In 28 locations a severe copper shortage was determined and in 9 locations a
marginal deficiency. Zinc shortage was severe in 28 locations and marginal in 17. Deficiency in
manganese was more rare and was determined in 9 locations. The areas where severe copper and
zinc shortage was observed were situated in the Rift Valley, the Omo valley, the province of Wollega
and the area around Lake Tana (Figure 3A).
- 11 -
Figure 3: A. Mineral deficiency in forage samples – B. Mineral deficiency in plasma samples
(Faye et al., 1986)
Analysis of plasma samples showed severe shortage of copper in 11 locations and marginal shortage
in 24 locations. Remarkable is that the severe deficiencies and a minority of the marginal shortages
were situated in the Rift Valley (Figure 3B).
Based on pedogeological maps of the country and the results of the survey a sketch was drawn,
describing the mineral status of cattle in Ethiopia and Eritrea (Figure 4). This map is only a rough
representation of the situation and naturally more research needs to be performed to complete the
map (Faye et al., 1986).
Figure 4: zones of mineral shortages in cattle in Ethiopia and Eritrea (Faye et al., 1986)
- 12 -
1.2.3 Jimma
Jimma is comfortably the largest settlement in western Ethiopia, with a population estimated at around
175.000 in 2008 (Briggs, 2009). The Gilgel Gibe dam is situated about 50 km in the West of the city. In
this region Dermauw et al. (2009) investigated the influence of altitude of grazing areas on the mineral
status of cattle. Cattle grazing in lower altitudes had a lower copper status than cattle grazing in higher
altitudes. Since there were significant differences in copper status between different herds at the same
altitude, the study concluded that there must be other factors influencing copper status (Dermauw et
al., 2009).
During a research around subclinical mastitis 11 dairy farms were visited in Jimma. Analysis of plasma
samples showed that 37% of the dairy cows (crossbreeds Holstein Friesian x local zebu) had a
shortage of copper (Belay et al., 2009).
1.3 The copper cycle in the soil – plant – cattle system
1.3.1 Summary scheme
Figure 5: the copper cycle in the soil – plant – cattle system (adapted from Howard et al., 1962;
Hall et al., 1979; Brennan et al., 1980; Humphries et al., 1983 Adriano, 1986; CDA, 1988; Butler,
1989; Bank et al., 1990; Faye et al., 1991; Stable et al., 1993; Xin et al., 1993; Underwood and
Suttle, 1999; Whitehead, 2000; Baissa et al., 2003; Baissa et al., 2005)
- 13 -
1.3.2 Parent material
The complex relations between the geochemical nature of soils and their parent materials, mineral
composition of plants and the occurrence of mineral deficiencies and excesses in grazing livestock
have been documented since the 1960’s (Webb, 1964).
In the Rift Valley, volcanic formations are mainly composed of basalt, ryolithe and trachyte and these
formations have high molybdenum and sulfur content. High concentrations of copper have been
reported in soils derived from basalts in Nigeria and Chad (Cottenie et al., 1981; Pias, 1968). Soils
developed on volcanic ash have low copper and zinc content (Reuter, 1975). West (1981) observed
that proportions of copper and molybdenum in soils derived from trachyte are such that molybdenum
induced copper deficiency is likely (West, 1981).
Jimma is situated in the Ethiopian volcanic plateau (FAO/UNESCO, 1975) and so the parental
materials in Jimma region are composed of basalt, ryolithe and trachyte. The Geological map of
Ethiopia (UN, 1972) shows the parental materials in Jimma and surrounding areas (Figure 6). The
region is divided in the magdala group and the ashangi group. The magdala group consists of
rhyolites, trachytes, rhyolitic and trachytic tuffs, ignimbrites agglomerates and basalts. In the Ashangi
group, the dominant parental materials are alkali olivine basalt and tuffs and rare rhyolites.
Unfortunately, the geological map is not very precise and so geological information in Jimma region
might be inaccurate and incomplete.
Figure 6: parental materials in Jimma and surrounding areas (adapted from UN, 1972)
Magdala group: rhyolites, trachytes, rhyolitic and trachytic tuffs; ignimbrites agglomerates, basalts
Ashangi group: alkali olivine basalt and tuffs, rare rhyolites
- 14 -
1.3.3 Soil
1.3.3.1 Association soil pH and bioavailability molybdenum and copper
Bioavailability of trace elements in soils is strongly influenced by the soil pH and appears to be related
to the concentrations of sodium and calcium (Maskall and Thornton, 1996). Alkali soils generally show
increased bioavailability of molybdenum while availability of copper decreases (Adriano, 1986).
Copper levels in wheat were found to decrease with increasing pH in several Kenyan soils (Nyandat
and Ochieng, 1976). On the other hand, strongly acid conditions can damage roots and interfere with
copper uptake by plants (CDA, 1988).
At Lake Nakuru National Park, the high molybdenum content of several plant species was linked with
the elevated pH of soils. The alkali tolerant grass species Sporobolus spicatus which grows on
alkaline solonetz soils had exceptional high concentrations of molybdenum (Maskall and Thornton,
1991). Particularly high molybdenum concentrations in Sporobolus spicatis in the Amboseli National
Park were also associated with alkaline soils (pH 9.2-10.7) (Maskall and Thornton, 1996).
1.3.3.2 Soil types around Jimma
The most common soil types around Jimma are nitisols and planosols. Less common are vertisols and
ferralsols (Deckers et al., 2008).
Nitisols are the most intensively cultivated soils in Ethiopia with area coverage of 12% of the total area
of the country and nitisols rank first in terms of area coverage of arable lands (23%) (FAO, 1984). This
soil type is a well drained, red, tropical soil (Figure 7A) that is rich in iron and is predominantly found in
level to hilly land in tropical rain forest or savannah vegetation. They are generally considered to be
fertile soils and have favourable physical properties. Nitisols belong to the most productive soils of the
humid tropics and are widely used for plantation of coffee and for food crop production (Yerima and
Van Ranst, 2005). Nitisols in Kenya had relative low pH (4.2-6.4) and relative low concentrations for
sodium and calcium. At the same time the superficial horizon of the nitisols was relatively rich in trace
elements (37.9 mg/kg Cu and 4.2 mg/kg Mo) (Maskall and Thornton, 1996). The low pH and relative
high amount of copper in nitisols might be favourable characteristics for copper content in the
vegetation but high amounts of iron might interact with availability of copper. Ferralsols have similar
geochemistry as nitisols (Bowell, 1993).
Figure 7: A. Cow in fertile nitisol area – B. Cattle grazing in poor wetland planosol area
- 15 -
Planosols have bleached and light coloured surface soil abruptly overlying finer subsoil. They have
light forest or grass vegetation and are seasonally or periodically wetlands (Figure 7B). These lands
soak up water during the raining season and than slowly release it. Wetlands cover approximately
1.4% of Ethiopia’s land surface and the most dominant wetland types in the country are swamps and
marshes (FAO, 1984; Hillman, 1993).
In the Ethiopian highlands, planosols occur in association with vertisols in lower parts of the landscape
and with nitisols in higher areas. Planosols are poor soils that are typically used for brick making and
extensive grazing. Generally, they are not used for agriculture. Mature planosols are chemically
strongly degraded and have low cation exchange capacity (Yerima and Van Ranst, 2005). The
superficial horizon of planosols has a pH around 6.3 (Zhiyi, 1989). Planosols in Slovakia had an
average copper content of 23.5 mg/kg and 0.9 mg/kg molybdenum (Lastincova et al., 2003) but these
amounts might not represent the composition in planosols around Jimma.
1.3.3.3 Influence of altitude on mineral concentrations in nitisols
Baissa et al. (2005) examined the effects of altitude on status of minerals in nitisols in Western
Ethiopia. Nitisol is also the dominating soil type around Jimma. Concentrations of extractable copper,
zinc and molybdenum were determined. Values of extractable copper were below the critical level in
18, 3.6 and 1.8% of the soil samples collected in respectively low, mid and high altitude. Although
there seems to be a trend to more deficient soil samples in the lower areas, altitude had no significant
influence on amount of extractable copper. Altitude had also no significant effect on molybdenum and
zinc status in nitisols (Baissa et al., 2005).
On the other hand altitude had a significant influence on concentrations of iron and manganese in
nitisols. The amounts of extractable iron and manganese are increasing with increasing altitude
(Baissa et al., 2003).
1.3.3.4 Influence of altitude on mineral concentrations in plants
Research to evaluate the effect of altitude and parent material on the mineral composition of forages
was conducted in the Mt. Elgon region. Mt. Elgon is an extinct volcano on the border between Kenya
and Uganda. This study showed a significant influence of altitude on concentrations of copper and
selenium in grasses. At lower areas only low copper (<6 mg/kg) and selenium values (<0.1 mg/kg)
were found in forages but values ranged widely at higher altitudes. Altitude had no significant influence
on other trace elements (Jumba et al., 1995).
1.3.3.5 Influence of altitude on mineral concentrations in cattle
The study conducted by Dermauw et al. (2009) has proven that altitude has an influence on the
mineral status of cattle. During this research, the Gilgel Gibe Catchment was divided in 3 regions,
based on their altitude. Cattle originating from the area on medium and high height had higher copper
concentrations in plasma than cattle in the lower areas. Because herds also differed significantly in the
same region, this parameter seemed to be very variable. Next to the altitude of the grazing lands,
there must be other factors that have an influence on copper status of cattle. Furthermore, zinc levels
- 16 -
were significantly higher in the middle area than in the lower and higher areas. Sulfur and iron showed
no significant difference between the 3 regions.
1.3.4 Plants
1.3.4.1 General
Trace element concentrations in tropical pastures can fall as the plant matures (Gomide et al., 1969)
and during periods of rapid growth (Fleming, 1973). According to available data copper contents are
extremely variable between plant species in tropical areas, particularly between grasses and browse
plants. In Lake Nakuru National Park grasses tend to contain higher levels of copper than browse
plants (Maskall and Thornton, 1991). In irrigated areas or in swamps, some grass species were
severely deficient in copper, whereas woody species and grass plants had copper concentrations
above normal (Faye, 1985). Shrub species draw their nutrients from deeper down and consequently
have a different trace element composition (Faye and Tisserand, 1989).
1.3.4.2 Copper antagonists
Higher concentrations of iron, molybdenum, zinc and sulfur decrease bioavailability of copper in plants
(see 1.1.2 Copper metabolism).
1.3.4.3 Tannins
Tannins in plants form insoluble mineral complexes and this can lead to reduced availability of
minerals (South and Miller, 1998). These substances are phenolic compounds and are subdivided in
condensed and hydrolysable tannins. The hydroxyl groups on the aromatic rings are chemically
reactive and form indigestible complexes with proteins. Condensed tannins have been reported to
interfere with iron absorption (Butler, 1989). Cattle and sheep are sensitive to condensed tannins,
while goats are more resistant (Kumar and Vaithiyanathan, 1983). In general, woody plants contain
higher levels of tannins than grasses (Iason and Van Wieren, 1999).
In the Gilgel Gibe Catchment, samples were collected from the main consumed plants in 6 regions.
The average tannin concentration per region ranged between 0 and 3.8% on dry matter base. High
tannin levels were associated with a decrease in copper plasma concentration in cattle while plasma
iron levels were not affected (Kechero et al., 2010).
1.3.4.4 Season
An increase in trace element concentrations of plants has been observed in the wet season for
pastures in the Kenyan highlands (Howard et al., 1962), for grass species adjacent to Lake Nakuru
(Maskall, 1991) and for several grass and browse species in Mole National Park in Ghana (Bowell and
Ansah, 1993). In Western Sudan, forages were adequate in copper during the wet season and
deficient during dry season. Serum copper levels were low throughout the year but particularly low in
the mid rainy season and late dry season (Abdelrahman et al., 1998).
- 17 -
Contamination of vegetation by soil dust increases in the dry season. Because iron and iron salts are
abundant in African soil types there is an increase of iron concentration in plants (Faye et al., 1991).
Grass cover becomes scarcer as the dry season progresses. In this way, the amount of ingested soil
increases in the diet of grazing cattle (Abrahams and Thornton, 1994).
1.3.5 Cattle
1.3.5.1 Fysiological status
Liver copper levels decline drastically in late pregnancy. Xin et al. (1993) reported a decrease of liver
copper by 51% from 8 weeks pre-partum until parturition. This decline is attributed to the drainage of
copper by the foetal liver at an exponential rate. Liver copper concentration is still lower 2 months after
parturition compared to copper levels before the pre-partal decline. Xin et al. (1993) observed lowest
copper levels in plasma 5 weeks pre-partum which does not coincide with changes in liver copper.
1.3.5.2 Infection
Inflammation and infection increase plasma levels of the copper containing ceruloplasmin as part of
the acute phase response (Disilvestro and Marten, 1990; Stable et al., 1993). Ceruloplasmin permits
the incorporation of iron in transferrin and consequently free ferrous iron concentrations decrease. In
this way, ceruloplasmin plays an important role in anti-oxidant and antibacterial defence (Carver et al.,
1982; Letendre and Holbein, 1984).
Mastitis can result in lowered copper serum concentrations. Mastitis leads to secretary disorders in the
mammary glands and increased permeability of blood capillaries. After E. coli infection, the mean
serum concentration of copper measured 52% of pre-challenge concentration. Experimental cows
were however marginal deficient in copper before infection and decline in mean serum copper
concentration was not significant (Erskine and Bartllet, 1993). Infection with S. aureus resulted after
24h in a serum copper concentration of 89% compared to concentration before infection. However,
mean copper concentration did not differ significantly in time (Middleton et al., 2004). Another study
showed no significant differences in serum copper levels between healthy cows and cows with
subclinical and clinical mastitis (Ibtisam El Zubeir et al., 2006).
1.3.5.3 Parasites
A depression of blood copper levels has been reported in ruminants infected with nematodes
(Bremner, 1959; McCosker, 1968; Frandsen; 1982). Bank et al. (1990) concluded that gastrointestinal
nematodes interfered with copper metabolism by causing an increase in pH in the abomasal and
duodenal part of the digestive tract. Other studies have proven that parasitism enhances copper
deficiency by influencing the molybdenum and sulfur antagonism (Ortolanie et al., 1993; Frandsen,
1982). The results from Adogwa et al. (2005) suggest that interaction with the absorption of copper in
the gastrointestinal tract is not the only mechanism by which the gastrointestinal parasites interfere in
the copper metabolism. In their study parasitism had a negative effect on blood copper levels even
when copper was administered parentally.
- 18 -
Next to gastrointestinal parasites, also blood parasites can decrease blood copper levels. Animals
infected by Babesia show lower iron and copper serum levels, while iron and copper serum
concentrations increased one month after treatment of infected animals (Askar et al., 2008). Infection
with Theileria annulata can also depress iron and copper levels in cattle (Omer et al., 2003). Copper
deficient animals could also be more susceptible to trypanosome infection than animals with normal
copper levels (Crocker et al., 1992).
1.3.5.4 Geophagy
Soil ingestion or geophagy is a phenomenon that is widespread in ungulates and other animals
although this behaviour is not exhibited everywhere (Kreulen and Jager, 1984; Mahaney and
Hancock, 1990). The geophagic soil contains high amounts of clay and fine silt with little sand
(Krishnamani and Mahaney, 2000). Ingested soils are usually situated on older, stable landscape sites
where they had ample time to reach maturity and even old age. In this way they have passed through
many stages of weathering where primary minerals have been transformed into secondary minerals
(Mahaney, 1999).
The reason why animals deliberately ingest soil is not completely known. One theory suggests
geophagy serves a detoxification function in relation to plants secondary compounds (Johns and
Duquette, 1991). Another explanation concerns the contribution of ingested soil to dietary mineral
intake. Studies on soil consumption by people in Africa and Central America indicated that in certain
cases these clays are important sources of supplementary minerals such as calcium, copper, iron,
magnesium and zinc. Stoszek (1976) observed that while three grass-fed cattle became severely
copper deficient, a fourth animal, which had the habit of eating soil, accumulated copper.
Furthermore, animals seem to prefer ingesting soil from termite mounds. Termite mounds seem to
contain higher concentrations of minerals than surrounding soils and a higher amount of plant species
is present close to the termitaria (Holdo and McDowel, 2004). It is likely that termites, in their
mobilisation of the soil, concentrate metals including copper (Kebede, 2004).
However, when accidentally ingested soil contributes 10% in the diet of sheep, Cu absorption and
utilisation are reduced as much as 50%. Even when the diet contains only 2% of soil the utilisation of
copper is significantly reduced. The antagonism between copper and ingested soil is strongly
suggested to be caused by iron amounts in soil (Suttle et al., 1975; Suttle et al., 1984; Underwood and
Suttle, 1999). Soil ingestion was measured in heifers by determining soil concentrations in faeces.
Calculations showed an intake of 0.73 and 0.99 kg soil per animal each day (Mayland et al., 1977).
Nitisols around Jimma are rich in iron and therefore it is likely that copper utilisation is reduced in cattle
grazing on nitisols by accidental nitisol ingestion.
- 20 -
2.1 Prevalence of copper deficiency
A survey was conducted at Jimma municipal abattoir to estimate the prevalence of copper deficiency
in the Gilgel Gibe valley. Jimma zone is situated in the south western part of the country in the
regional state of Oromia. The town is located at approximately 350 km south west of the capital Addis
Ababa. In 2003, Jimma district had a livestock population of 18354 cattle (CSA, 2003). Slaughter
animals are coming to Jimma municipal abattoir from different areas surrounding the town.
During meat inspection of slaughtered cattle, 53 animals were selected. All animals were adult, male
cattle from local breed, further selection was at random. Since copper values in the liver are the
golden standard for determining copper deficiency in cattle, approximately 50 g of liver tissue was
collected of all selected animals. The presence of parasitic infections was determined in these
sampled livers by inspection. Samples were placed on plastic petri dishes and were oven dried at 65°
C for 72 hours. Afterwards, dried samples were grinded in a mechanical grinder and stored in closed
tubes.
Destruction of liver samples happened by an accelerated wet digestion method. One gram of each
dried and grounded sample was weighed after which 10 ml of HNO3- was added. Samples were stirred
in an ultrasonic bath for 15 minutes at room temperature. Subsequently, samples were destructed by
open microwave method. After digestion was complete, dilutions were made to meet analytical
requirements (Campbell and Whitfield, 1991). Levels of Zn, Cu and Fe were determined through ICP-
OES.
2.2 Evaluation of management practices
2.2.1 Study area
The study was conducted in the Gilgel Gibe Catchment in the south western part of the country in the
regional state of Oromia. The catchment has an altitude ranging between 1059 and 3259 meter above
sea level. The two raining seasons in the region are the kiremt and the belg. The kiremt lasts from
mid-June to mid-September and during this season 90-95% of the nation’s total cereals output is
produced. The belg receives rainfall from February to May and only provides 5-10% of the cereal
output (USDA/FAS, 2008). The survey was started at the end of the kiremt, from September to
October.
The study area, located at the southern part of the Gilgel Gibe Catchment and within a radius of 35 km
from Jimma, was divided in 3 regions based on their altitude. Region 1 was situated between 1700
and 1800m, region 2 between 1800 and 2000 meters and region 3 between 2000 and 2200 meters. In
each region, 6 herds were selected at random (in region 3, one extra herd was included in the study).
In each herd, one representative animal was selected: female, between the age of 4 to 6 years, not
pregnant and preferably not lactating. Because farmers in the region don’t have the habit to wean their
- 21 -
calves, animals lactating for more than 4 months were allowed in the survey. Cows that were lactating
less than 4 months were not included because liver copper concentration is still lower 2 months after
parturition compared to copper levels before the pre-partal decline (Xin et al., 1993). The selected
animals were numbered according to the date of observation (Figure 8).
Figure 8: locations of the selected cattle in the Gilgel Gibe Catchment in association with the
altitude of their grazing lands (Adapted from Van Ranst et al., 2010)
2.2.2 Soil and geophagy
The most dominating soil types around Jimma are the nitisols and the planosols. Less occurring types
are the ferralsols - associated with the nitisols - and the vertisols - associated with the planosols.
Because of similar appearance of the soils, no distinction was made between nitisols and ferralsols
and between planosols and vertisols.
Soil types were distinguished by colour in two groups. Group PV includes the planosols and the
vertisols and this group had a soil colour from grey to black. Planosols and vertisols become wetlands
during the raining season and are covered with light forest or grass vegetation. These areas are poor
soils that are generally used for brick making and extensive grazing.
The NF group contains the nitisols and the ferralsols and colour is red to brown. These soils are
productive, fertile soils that are widely used for plantation of coffee and food crops. The NF group is
found in higher areas than the PV group and are rich in iron.
During the observation of the selected animals, attention was given whether or not animals were
ingesting soil deliberately.
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2.2.3 Management practice
Different management practices were determined by selecting different criteria. According to their
grazing strategy, herds were classified in 2 groups. The first group contained herds grazing on
communal areas. Farmers can leave their cattle to the communal grazing lands where one or more
herders look out for their cattle. In the evening farmers return to the communal grazing areas to collect
their cattle and return their animals to the stables. In this way, a large herd belonging to different
farmers is formed every day and herded by a limited amount of people. The second group contained
small herds belonging to an individual farmer.
Herd size was classified in 3 groups: less than 10 animals (1), between 10 and 40 animals (2) and
more than 70 animals (3). BCS of observed animals was determined using an adapted condition
scoring for zebu cattle, scaled from 1 to 9 (Nicholson and Butterworth, 1986).
Route and distance covered by the observed animals were monitored by GPS tracking. All
observations were entered into a geographic information system (GIS) as text files and referenced
according to their distance bearing from home. Total covered distance was measured from the
moment cattle left their stable in the morning until return in the evening. Herding radius was defined as
the maximum distance from home at which a herd was observed during that day. By comparing the
total covered distance and the herding radius, different herding practices could be determined and
influence on mineral status could be evaluated.
2.2.4 Plant intake
Estimation on the plant composition of the diet was realised by observation. During one grazing day
the selected animal was observed from the moment leaving the stable in the morning until return in the
evening. Every 10 minutes the ingestion of plant species was recorded. In case a bite was taken from
several plant species at the same moment, the involved plant species were recorded. Based on these
results a score sheet of the ingested plant species could be calculated for each observed cow. One
plant observation received 1 point. When more species were recorded during one observation, the
involved plant species received 1 point divided by the amount of species recorded at that moment.
When these scores were divided by the number of total observations, estimation could be made on
the proportions of the ingested plant species.
Samples of the most important plant species were collected in paper bags and oven dried at 65° C for
72 hours. Afterwards, dried samples were grinded in a mechanical grinder. Samples were stored in
plastic bags until Zn, Mo, Co, Cu, Mn and Fe were determined with ICP-OES and Se and S through
ICP-MS analysis.
Destruction of plant samples happened by an accelerated wet digestion method. One gram of each
dried and grounded sample was weighed after which 10 ml of HNO3- was added to each sample.
Samples were stirred in an ultrasonic bath for 15 minutes at room temperature. Unlike destruction of
liver samples, destruction of plant samples happened in a microwave utilizing closed vessels. By the
- 23 -
combination of heat and pressure in a closed vessel, reaction rate increases and digestion time
decreases (Vigler et al., 1980; Okamoto and Fuwa, 1984).
To determine the estimated mineral intake we could use the data on the proportions of the ingested
plant species. The percentage of each ingested plant was multiplied by the mineral content of the
species. When mineral concentrations were not known for all species a correction factor was
introduced to extrapolate the mineral concentration of the known percentage of ingested plants to
100%. In this way mineral intake by cattle could be compared between the different regions.
2.2.5 Blood sampling
To prevent stress during the observation, blood samples were taken when animals returned to their
stable. After fixating the animal, blood was collected from the jugular vein in two heparin tubes of 6 ml.
The blood samples were immediately transported in ice water to the Agricultural Campus of Jimma
University.
First, the presence of blood parasites was determined in the blood, more specifically for Babesia and
Trypanosoma. Giemsa stained blood smears were used to examine infection with Babesia. Giemsa
colouring was obtained by air drying a thin blood smear, after which fixation of the sample occurred in
methyl alcohol for 2 minutes. After drying, the sample was stained by Giemsa stain 10% for 30
minutes. Finally, the blood smear was examined by microscope for the presence of intracellular
parasites in the red blood cells.
Infection with Trypanosoma was checked by the haematocrit centrifugation technique described by
Woo (1970). Capillary tubes were filled with blood sample and sealed at one end using plasticin, than
centrifuged for 7 minutes at 3500 rates per minute. Afterwards, the buffy coats of the tubes were
examined for the presence of trypanosomes using a microscope.
The remaining blood samples were centrifuged for 10 minutes at 3500 rates per minute. Plasma was
collected and samples were temporarily stored in the deep freezer. Copper, iron and zinc were
analysed by ICP-OES and manganese through ICP-MS analysis. Similar to the destruction of plant
samples, an accelerated wet digestion method utilising closed vessels was used for the destruction of
plasma samples.
2.2.6 Statistical analysis
Statistical analysis was performed on all data using SPSS17 (SPSS Inc., Illinois, Chicago).
Independent t-tests and one-way ANOVA with Tukey post-hoc tests were used to determine
differences between groups. Pearson correlations were used to determine interrelationships between
selected parameters.
- 25 -
3.1 Prevalence of copper deficiency
Liver samples collected at Jimma municipal abattoir were subdivided in different classes, dependant
on their copper concentrations. Classification occurred according to the criteria of Puls (1988) and
Kincaid (1999): clinically deficient (<20 mg/kg), deficient (<33 mg/kg), marginal (33-125 mg/kg),
adequate (125-600 mg/kg) and high (>600 mg/kg) (Table 4).
Based on these data, estimation was made on the prevalence of copper deficiency in the area. On the
total of 53 inspected bulls, 43 animals were in the deficient range while only 10 cattle had adequate
concentrations. An overall prevalence of copper deficiency in the area was estimated at 81% (43/53).
In the deficient cattle, a distinction was made between clinically deficient, deficient and marginal
deficient. Clinically deficient copper concentrations were measured in 25 cattle, 7 cattle had deficient
levels and 11 animals were in the marginal range. These results indicate shortage of copper as a
severe problem in the region.
Liver of cattle normally contains between 45 and 300 mg/kg iron based on wet matter (Puls, 1988). In
the 53 sampled animals, 3 animals or 6% had iron levels above 300 mg/kg. All other samples were in
the adequate range. Except for one sample, all animals had zinc levels between 25 and 200 mg/kg
and were in the normal range (Puls, 1988).
Table 4: classification liver samples (Adapted from Kincaid, 1999; Puls, 1988)
Cu Fe Zn
n % Range DM (mg/kg) n % Range WM
(mg/kg) n % Range DM (mg/kg)
Clinically deficient 25 47 <20 - - - - -
Deficient 7 13 <33 - - <40 - - <20-40
Marginal 11 21 33-125 - - - - 25-40
Adequate 10 19 125-600 50 94 45-300 52 98 25-200
High - - >600 3 6 53-700 1 2 300-600
Total 53 100 53 100 53 100
DM= Dry Matter, WM= Wet Matter
Because parasites can influence mineral status, presence of parasitic infections in sampled livers was
determined by inspection. No distinction was made in the extent of infection. Only 8 samples were
uninfected. Fasciola spp. was the most common parasite found in sampled livers. Six cattle were
infected with Echinococcus granulosus and one animal had Ascaris spp. in the liver (Table 5).
- 26 -
Table 5: parasitic infections in sampled livers
Parasite n %
Ascaris spp. 1 2
E. granulosus 6 12
Fasciola spp. 38 71
Uninfected 8 15
Total 53 100
An independent t-test was conducted to compare mineral levels of uninfected livers with infected
livers. No significant differences were calculated. Figure 9 shows concentrations of copper in relation
to concentration of iron. Remarkable is that high iron levels in liver only occurred when copper values
were deficient. Higher amounts of copper were typically accompanied by lower iron values.
.
Figure 9: correlation between copper (mg/kg) and iron (mg/kg) values in livers collected in the
Jimma abattoir, Ethiopia
- 27 -
3.2 Management practices
3.2.1 General
Management practices in the different regions are shown in Table 6. The selected animals were
numbered according to the date of observation. Herds were subdivided in communal (C) or individual
(I) herds and were classified in 3 groups according to the number of animals in the herd. A difference
was made between grazing (G) animals and cattle that were fed with crop residues (CR). The
percentage of crop residues in diet was estimated by observation. Stovers from Saccharum
officinarum, Sorghum spp., Zea Mays and Pisum sativum, leaves from Musa spp. and Ensete
ventricosum and residues from Eragrostis tef and Linum usitatissimum were considered as crop
residues.
Total distance (TD) and herding radius (HeRa) are expressed in km. The amount of ingested plant
species (AIPS) is a factor expressing diversity in diet.
Table 6: management practices in the different height regions around Jimma, Ethiopia
Reg Cow ID SOIL Wet
Land Man Herd size
Feeding strategy
Crop Residue TD HeRa AIPS BCS
Observed supplementation
by farmer 1 1 PV 1 C 3 G 0,0 3,7 0,5 9 2 - 1 2 PV 0 I 1 G 2,3 4,4 1,1 18 6 - 1 3 PV 1 C 3 G 0,0 5,6 1 9 5 -
1 4 PV 1 I 1 G 0,0 1,5 0,26 8 5 Around 2 kg of corn enriched with salt
1 6 PV / NF 1 I/C 2 G 0,0 5,9 1 11 5 - 1 7 PV 1 C 3 G 0,0 6,3 0,73 14 4 -
2 5 NF 0 C 2 G 2,3 6,1 1,3 12 3 One leaf from Ensete ventricosum and one leaf from Musa spp.
2 10 NF 0 I 1 G 2,7 0,9 0,35 18 4 - 2 11 NF 0 I 1 G/CR 13,2 0,7 0,22 20 6 -
2 12 NF 0 I 1 CR 50,0 0,05 0,02 13 5
Stover from Zea mays, leaves from Rhus
glutinosa and Premna schimperi
2 16* PV 1 C 1 CR 66,7 1,6 0,36 6 7 Bulule once a week
2 17* NF 0 I 1 CR 52,1 0,55 0,17 9 7 Bulule tree times a week
3 8 NF 0 I 1 G 0,0 1,6 0,35 11 5 -
3 9 NF 0 I 1 G 0,8 1,8 0,38 26 4 Herbal mixture from pea field
3 14 NF 0 I 1 G/CR 27,5 0,36 0,06 14 4 Pennisetum purpureum, Saccharum officinarum, Stover from Zea mays
3 15 NF 0 I 1 G/CR 21,9 1,5 0,33 18 5
Melinis repens, Pennisetum purpureum,
stover Zea mays, Erythrina brucei
3 18 NF 0 I 1 G/CR 39,5 4,1 0,79 22 5 - 3 19* NF 0 I 1 G/CR 27,3 1,7 0,58 21 5 - 3 13 NF 0 I 1 G 1,0 3,2 0,88 22 5 -
Reg= Region (1= 1700-1800m; 2= 1800-2000m; 3= 2000-2200m), *= changed feeding strategy few days before observation,
PV= Planosol/Vertisol, NF= Nitisol/Ferralsol, Man= Management (C= Communal grazing, I= Individual herds), Herd size (1=
<10; 2= 10-40; 3= >70 cattle) G= Grazing, CR= Crop Residues, Crop residues (% of total diet), TD= Total Distance (km),
HeRa= Herding Radius (km), AIPS= Amount of Ingested Plant species, BCS= Body Condition Score (1-9)
- 28 -
3.2.2 Background information
From the 19 observed farmers, 8 farmers presented supplementary food to their animals. Cow4
received every day around 2 kg of corn enriched with salt before the animal was herded on grazing
pastures.
One large leaf from Ensete ventricosum (false banana) and from Musa spp. (banana) was given daily
to cow5 (Figure 10A). Ensete ventricosum is locally known as ‘kocho’ and the pseudo stems and
underground rhizomes from this plant serve as an important food source for people from the region.
One farmer supplemented his animals with a herbal mixture cut from his pea field (Figure 10B). In the
morning around 0.4 kg from this mixture was presented to each of his animals. Early in the afternoon,
the farmer brought his animals back home from the grazing pasture. In stable, approximately 5 kg
from the same mixture was again presented to each animal.
Farmers 12, 15 and 16 offered a lot of forages to their animals in the morning. These forages include
crop residues such as Saccharum officinarum (sugar cane) (Figure 10D) and Zea mays but also cut
grass from Melinis repens (Figure 10E), Pennisetum purpureum (elephant grass) (Figure 10C) and cut
branches from Premna schimperi, Rhus glutinosa and Erythrina brucei.
Figure 10: Supplementary food presented by farmers; A: Leaf from Ensete ventricosum and
Musa spp. – B: Herbal mixture from pea field – C: Pennisetum purpureum – D: Chopping
Saccharum officinarum – E: Melinis repens, cut from a private field
- 29 -
Two animals (cow16 and 17) were supplemented with a local product known as ‘bulule’. This product
consists mainly of sorghum and corn and a small amount of teff. After grinding this grain mixture,
water is added to the powder. The obtained flour is packed first in the leaves from Ensete ventricosum
after which the product undergoes fermentation during one night. Bulule was given once every week
to cow16 and 3 times a week to cow17.
Not a single cow on the PV- or NF pastures ingested soil deliberately (geophagy).
3.2.3 Statistical analysis
When herders applied communal grazing, a significant increase in total distance (4.87 km +/- 0.76)
and herding radius (0.82 km +/- 0.14) was observed, compared to individual herds (respectively 1.72
km +/- 0.38 and 0.42 km +/- 0.09). Animals fed with crop residues covered significant lower total
distance (1.32 km +/- 0.45) and herding radius (0.32 km +/- 0.09) than grazing animals (3.73 km +/-
0.62 and 0.71 km +/- 0.11).
No residues from crops were present in diets of cattle from region 1. Due to local circumstances,
animals were first observed in region 1 when local crop fields were not yet harvested. The percentage
of crop residues in diet is strongly correlated with the date of observation (R = 0,744**) using Pearson
correlations. For this reason it is more likely that the percentage of crop residues in diet depends on
the date of observation and not related to region.
BCS did not differ significantly between cows from communal or individual herds. Cow16, 17 and 19
changed management and feeding strategy few days before observation. In stead of grazing on
pastures, these cattle were fed with crop residues on the moment of observation. Consequently, the
management of these animals could not be related to their BCS. When these animals were not
included in statistical analysis, BCS tended to be lower in communal herds. The BCS from cattle that
received supplementary food by farmers did not differ significantly from cattle without
supplementation.
Statistical analysis was conducted to compare management practices between the different regions
(Table 7A) and the different soil types (Table 7B). Management of cattle grazing in Region 1 and
associated planosols/vertisols differed significantly from cattle grazing in Regions 2 and 3 and
associated nitisols/ferralsols. On PV-soils, cattle were typically held in larger herds grazing on
communal lands while cattle on NF-pastures typically grazed in individual smaller herds. The total
distance covered by cattle on PV was higher than cattle held on NF. The amount of ingested plant
species was lower in the PV-areas and higher in NF. These results indicate that PV-areas have a
poorer diversity in plant species and cattle held on NF-pastures have a more varied diet.
Table 7: the link between management practices in the different regions (A) and the different soil types (B)
A. REGION 1 REGION 2 REGION 3 SEM P C 0,67 0,33 0,00 0,11 0,037 Herd 2,17 1,17 1,00 0,18 0,007 TD 4,57 1,65 2,04 0,49 0,022 HeRa 0,77 0,40 0,48 0,09 0,217 AIPS 11,50 13,00 19,10 1.31 0,026 BCS 4,50 5,33 4,71 0.28 0,490
- 30 -
B. PV NF SEM P C 0,71 0,08 0,11 0,002 Herd 2,00 1,08 0,18 0,008 TD 4,14 1,88 0,49 0,029 HeRa 0,71 0,45 0,09 0,152 AIPS 10,71 17,17 1.31 0,009 BCS 4,86 4,83 0.28 0,972
Region (1= 1700-1800m; 2= 1800-2000m; 3= 2000-2200) PV= Planosol/Vertisol, NF= Nitisol/Ferralsol, SEM= Standard Error of
the Mean, C= Communal grazing, Herd= Herd size (1= <10; 2= 10-40; 3= >70 cattle), TD= Total distance (km), HeRa= Herding
Radius (km), AIPS= Amount of ingested plant species, BCS= Body Condition Score (1-9)
3.3 Plant composition of the diet
3.3.1 General
Estimates of the plant composition of the diet were realised by observation. In total, 87 different plant
species from 25 families were observed. Four plant species could not be identified by their scientific
name but were recognised by local farmers as lima, matane, mito and tokomo. One plant species was
not identified and was not recognised by farmers. The proportions of ingested plant species by the
observed cows are shown by Table 15 (Addendum). A 100% stacked bar chart was made on the plant
species composition of the diet for each region for better interpretation of the data (Figures 11, 12 and
13).
Figure 11: plant composition diet region 1 (1700-1800m)
- 31 -
Figure 12: plant composition diet region 2 (1800-2000m)
Figure 13: plant composition diet region 3 (2000-2200m)
- 32 -
3.3.2 Background information
3.3.2.1 Diet composition according to region
The botanical composition of diets according to region is shown by Figures 11, 12 and 13. Since
region is strongly associated to soil type, reference about botanical composition is made to 3.3.2.2
(Diets in Planosols/Vertisols) and 3.3.2.3 (Diets in Nitisols/Ferralsols).
3.3.2.2 Diets in Planosols/Vertisols
All observed cows in region 1 and cow16 in region 2 grazed on planosols/vertisols (PV), all others
were herded on nitisols/ferralsols (NF). Each grazing pasture in the PV-area was wetland except the
pasture where cow2 was herded. This pasture was situated at a higher altitude than a nearby marsh
so water in this pasture could easily be drained to the swamp. From all PV-areas, diversity of ingested
plant species was highest by the observed animal grazing on this pasture.
Remarkable was the one-sided diet in the PV areas where Cyperus- and Cynodon spp. were the most
dominant grazed vegetation. Cow16 also grazed on a planosol pasture but no ingestion of Cyperus- or
Cynodon spp. was observed. This is because this animal was observed in a later period when several
wheat fields were already harvested. In stead of grazing the Cyperus- and Cynodon dominated
grasslands, cattle feed themselves with crop residues on yielded crop fields in a later period of the dry
season. The most common ingested herbs were Centella asisetica and Trifolium spp. Only very small
bites were taken from the leaves of shrubs and trees such as Eucalyptus camaldulensis, Psidium
guajava (guava) and Sesbania sesban. Ingestion of the leaves from Eucalyptus camaldulensis was
prevented by farmers because of the economic value of Eucalyptus trees as construction material.
3.3.2.3 Diets in Nitisols/Ferralsols
Next to Cynodon spp., 18 other ingested grass species were observed in the nitisol area. Just like the
observed animals on the planosols, only small amounts were eaten from shrubs such as Maytenus
obscura, Premna schimperi, Sesbania sesban, Vernonia adoensis etc. The leaves from the trees
Erythrina brucei and Rhus glutinosa were offered in small amounts to two animals.
In the nitisol areas, the proportion of crop residues in the diet increased when animals were observed
in a later period. Most presented crop residues were stovers from Zea mays, followed by Saccharum
officinarum (sugar cane), Sorghum spp. and Pisum sativum (pea). Also crop residues from Eragrostis
tef (teff) and Linum usitatissimum (flax) were digested by 1 observed animal. Leaves from Musa spp.
(banana) and Ensete ventricosum (false banana or ‘kocho’) were digested by 2 animals.
3.3.3 Statistical analysis
An independent t-test was conducted for the comparison of diets from PV and NF. Cattle grazing on
PV had significant higher percentage of Cyperaceae in their diet (35.64 +/- 6.32) compared to diets
from NF (5.76 +/- 1.46). Diversity in plant species was significantly lower in PV (10.71 +/- 1.54) than in
NF (17.17 +/- 1.53). A significant higher amount of herb species was ingested in NF (8.42 +/- 0.94)
than in PV (4.86 +/- 0.99). These results indicate a more varied diet in the nitisol/ferralsol areas.
- 33 -
3.4 Mineral composition of plant species
3.4.1 General
In total, 87 ingested plant species from 25 families were observed. Four plant species could not be
identified by their scientific name but were recognised by local farmers as lima, matane, mito and
tokomo. One plant species was not identified and was not recognised by farmers.
To evaluate the mineral composition of the most important plant species, a total of 66 plant samples
were taken from observed regions. Mineral concentrations were determined in 52 different plant
species. From the planosols, 13 samples were collected while 53 samples were collected in nitisol
areas. More plant samples were taken in the nitisols because plant variation was higher in these
areas. Samples from Cyperus spp., Cynodon spp. and Centella asiatica were taken in both planosols
and nitisols.
Mineral concentrations in plant samples are shown in Table 16 (Addendum). Generally, Table 16
indicates mineral imbalances in plant species as a widespread phenomenon in the Gilgel Gibe
Catchment.
3.4.2 Mineral composition plants according to region
A one-way ANOVA using the Tukey post hoc test was conducted to evaluate the mineral
concentrations of plant species between the 3 regions. Plant species from region 2 had significantly
lower molybdenum (0.58 mg/kg +/- 0.12) levels and higher copper:molybdenum ratio (28.2 +/- 4.62)
than species from region 3 (respectively 1.51 mg/kg +/- 0.33 and 9.68 +/- 2.03). Zinc concentrations
were significantly higher in region 1 (50.99 mg/kg +/- 9.31) than region 2 (27.90 mg/kg +/- 2.73).
3.4.3 Mineral composition plants according to soil type
An independent t-test was used to compare mineral concentrations in plant species between PV and
NF. No significant differences were detected. However, same plant species seem to differ in mineral
concentrations according to the soil type they grow on. Samples from Cynodon spp, Cyperus spp and
Centella asiatica were collected from both PV and NF (Table 8). Remarkable were the lower copper
and higher molybdenum concentrations in Cynodon- and Cyperus spp. collected in wetland PV,
compared to same species collected in NF. Mineral concentrations of Centella asiatica were similar in
well drained PV and NF.
- 34 -
Table 8: mineral concentrations of Cynodon spp., Cyperus spp. and Centella asiatica in
Planosol/Vertisols and Nitisol/Ferralsol
SOIL WET LAND Plant Species Cu
(mg/kg) Mo
(mg/kg) Cu:Mo Fe (mg/kg)
Zn (mg/kg)
S (%)
PV 1 Cynodon spp. 4,2 1,63 2,56 911 31,5 0,121 PV 1 Cynodon spp. 5,0 1,76 2,85 260 38,4 0,215 NF 0 Cynodon spp. 7,1 0,70 10,09 2398 36,4 0,145 PV 1 Cyperus spp. 4,2 1,56 2,70 338 42,2 0,133 PV 1 Cyperus spp. 4,6 2,28 2,02 3020 19,7 0,111 NF 0 Cyperus spp. 7,8 0,67 11,55 4240 69,1 0,189 PV 0 Centella asiatica 10,1 0,76 13,36 2809 88,4 0,431 NF 0 Centella asiatica 11,1 0,67 16,44 1827 105 0,573
Severely deficient
Marginally deficient
Marginally antagonistic
Highly antagonistic
Above the MTC
PV= Planosol/Vertisol, NF= Nitisol/Ferralsol, MTC= Maximum Tolerable Concentration
3.5 Mineral intake in selected cattle
3.5.1 General
Based on the plant composition of the diet of observed animals and based on the mineral composition
of sampled plant species, estimation has been made on the average mineral intake in selected cattle
(Table 9).
Table 9: estimated mineral intake in selected cattle per kg DM
REGION CowID SOIL Wet Land
Feeding strategy
Cu (mg/kg)
Mo (mg/kg) Cu:Mo Fe
(mg/kg) Zn
(mg/kg) S
(%) 1 1 PV 1 G 4,21 1,53 2,75 749 36,39 0,13 1 2 PV 0 G 5,59 1,13 4,95 639 40,35 0,15 1 3 PV 1 G 5,34 1,43 3,74 956 47,97 0,19 1 4 PV/NF 1 G 4,18 1,36 3,07 692 37,65 0,14 1 6 PV 1 G 5,12 1,46 3,51 828 43,16 0,16 1 7 PV 1 G 4,59 1,66 2,76 1094 36,64 0,14 2 5 NF 0 G 7,98 0,88 9,03 1676 49,70 0,27 2 10 NF 0 G 7,85 1,19 6,61 2084 49,58 0,25 2 11 NF 0 G/CR 6,49 0,54 12,04 1621 39,83 0,20 2 12 NF 0 CR 5,05 0,51 9,99 1577 49,29 0,15 2 16 PV 1 CR 4,10 1,71 2,39 400 32,29 0,14 2 17 NF 0 CR 4,52 0,62 7,33 682 26,43 0,13 3 8 NF 0 G 7,56 1,25 6,02 3855 51,12 0,21 3 9 NF 0 G 7,03 1,96 3,58 2300 42,68 0,18 3 14 NF 0 G/CR 7,41 0,73 10,20 1551 41,82 0,18 3 15 NF 0 G/CR 6,15 0,89 6,92 1212 33,31 0,13 3 18 NF 0 G/CR 4,99 0,61 8,12 1555 33,41 0,14 3 19 NF 0 CR 4,69 0,97 4,83 1000 37,69 0,15 3 13 NF 0 G 7,38 1,39 5,33 955 41,95 0,24
Severely deficient
Marginally deficient
Marginally antagonistic
Highly antagonistic
Above the MTC
Region (1= 1700-1800m; 1800-2000m; 2000-2200m), PV= Planosol/vertisol, NF= Nitisol/ferralsol, G= Grazing, CR= Crop Residue, MTC=
Maximum Tolerable Concentration
- 35 -
Table 9 indicates marginal intake of copper in all animals, ranging from 4.10 to 7.98 mg/kg per kg DM.
The amount of zinc was sufficient in all animals except one marginal shortage in cow17. Iron particles
were present in antagonistic concentrations in all diets. From the diets of 19 cattle, 11 had iron levels
even above the MTC. Molybdenum was present in marginal antagonistic concentrations in all diets
from cattle grazing on planosols/vertisols and in 4 of 12 cattle grazing on nitisols/ferralsols. Marginal
shortage of copper and marginal antagonistic concentrations of molybdenum resulted in a severe
disbalanced copper:molybdenum ratio in all diets of cattle grazing on planosols/vertisols, except cow2.
Cow9 is the only animal on nitisols/ferralsols with disbalanced copper:molybdenum ratio. Sulfur levels
were adequate in region 1 and in planosols/vertisols but marginally antagonistic in 5 cattle grazing on
nitisols/ferralsols.
3.5.2 Statistical analysis
3.5.2.1 Mineral intake in cattle according to region
A one-way ANOVA using the Tukey post hoc test was conducted to evaluate the mineral
concentrations in total diets between the 3 regions. The copper:molybdenum ratio of the total diet was
significantly lower in region 1 (3.46 +/- 0.34) than region 2 (7.89 +/- 1.36).
3.5.2.2 Mineral intake in cattle according to soil type
An independent t-test was conducted to compare mineral levels in total diet from cattle herded on PV
with cattle herded on NF. Mineral concentrations of total diet seem to be more associated with soil
type than with region. Statistical analysis indicates mineral intake by cattle is strongly influenced by
type of soil (Table 10). Cattle grazing on PV ingested significantly lower amounts of copper than cattle
herded on NF. On the other hand, molybdenum was significantly higher in the PV-group. Iron particles
were significantly higher in NF and lower in PV. No significant influence from soil type was present on
the amounts of zinc and sulfur in estimated diets, although there was a trend for sulfur.
Table 10: link between mineral concentrations in diet and soil type
PV NF SEM P Cu 4,73 6,43 0,31 0,005 Mo 1,47 0,96 0,1 0,003
Cu:Mo 3,31 7,5 0,66 0 Fe 765 1672 183 0,003 Zn 39,21 41,4 1,57 0,47 S 0,15 0,19 0,01 0,082
PV= Planosol/Vertisol, NF= Nitisol/Ferralsol, SEM= Standard Error of the Mean
3.5.2.3 Mineral intake in cattle according to feeding strategy
Pearson correlations were calculated to evaluate the impact of the proportion of ingested crop
residues, poaceae and herbs on mineral concentrations in total diet (Table 11).
- 36 -
Stovers from Saccharum officinarum, Sorghum spp., Zea Mays and Pisum sativum, leaves from Musa
spp. and Ensete ventricosum and residues from Eragrostis tef and Linum usitatissimum were
considered as crop residues. Higher percentages of crop residues in diet were significantly correlated
with lower amounts of zinc in total diet. Also total molybdenum and sulfur tends to be lower when
higher amounts of crop residues were included in diet.
Higher proportions of poaceae in diet are associated with lower molybdenum and zinc levels and a
more balanced copper:molybdenum ratio in total diet while higher percentages of herbs are
significantly correlated with higher molybdenum and zinc levels and a lower copper:molybdenum ratio.
Table 11: correlation between total mineral concentrations and % of crop residues, poaceae
and herbs in diet
Cu Mo Cu:Mo Fe Zn S Crop
Residues (%) Pearson
Correlation -0,389 -0,433 0,278 -0,248 -0,49 -0,435
P 0,1 0,064 0,249 0,306 0,033 0,063
Poaceae (%) Pearson Correlation -0,093 -,557 ,520 0,042 -,533 -0,22
P 0,704 0,013 0,023 0,863 0,019 0,365
Herbs (%) Pearson Correlation 0,148 ,571 -,512 0,011 ,461 0,234
P 0,546 0,011 0,025 0,965 0,047 0,335
3.6 Mineral concentrations in plasma of selected cattle
3.6.1 General
Plasma concentrations of copper, iron, zinc and manganese were measured in all observed animals
(Table 12). Ten observed cows had a severe shortage whereby cow19 was almost completely
depleted in copper (0.07 mg/l). A marginal deficiency was found in 6 animals. Only 3 animals had
adequate copper amounts in plasma. Even though cow12 had typical symptoms of copper deficiency
such as depigmentation around the eyes and back legs, adequate copper levels were found in this
animal. This may be caused by infection, in this case trypanosomiasis. For statistical analysis, plasma
copper concentrations were recoded in 3 groups: severely deficient (0), marginally deficient (1) and
adequate (2).
Iron concentrations were in the normal range for all animals except cow17 (4.09 mg/l). Marginal
deficient concentrations in zinc were measured in 7 cows. Normal concentrations of manganese were
measured in all animals.
Because infection can influence copper values in plasma, attention was given on the presence of
clinical signs of disease. Cows1 and 11 suffered from severe diarrhoea. Because dysuria and
- 37 -
stranguria were noticed in cow6, this animal was suspected of urinal infection. Trypanosomis was
diagnosed by microscope in cows5, 12 and 18. No Babesia was found in blood smears.
Table 12: mineral concentrations in plasma of selected animals
REGION CowID SOIL Wet Land
Cu (mg/l)
Cu (code)
Fe (mg/l)
Zn (mg/l)
Mn (mg/l) Extra
1 1 PV 1 0,41 0 2,28 0,75 0,047 Diarrhoea 1 2 PV 0 0,70 2 2,98 0,90 0,052 - 1 3 PV 1 0,32 0 3,21 0,88 0,035 - 1 4 PV 1 0,28 0 2,07 0,74 0,047 - 1 6 PV/NF 1 0,66 1 1,63 0,71 0,045 Urinal infection 1 7 PV 1 0,31 0 2,33 1,39 0,099 - 2 5 NF 0 0,53 1 2,32 0,98 0,051 Tryps 2 10 NF 0 0,66 1 2,15 0,71 0,037 - 2 11 NF 0 0,32 0 1,69 0,76 0,017 Diarrhoea 2 12 NF 0 0,73 2 1,80 0,78 0,018 Tryps 2 16* PV 1 0,45 0 1,78 0,96 0,035 - 2 17* NF 0 0,77 2 4,09 0,87 0,062 - 3 8 NF 0 0,33 0 3,49 0,78 0,030 - 3 9 NF 0 0,36 0 2,42 0,90 0,033 - 3 14 NF 0 0,61 1 1,98 1,15 0,037 - 3 15 NF 0 0,64 1 2,54 1,06 0,037 - 3 18 NF 0 0,56 1 2,29 1,12 0,043 Tryps 3 19* NF 0 0,07 0 2,49 1,01 0,045 - 3 13 NF 0 0,39 0 2,31 0,89 0,041 -
Region (1= 1700-1800m; 2=1800-2000m; 3=2000-2200m), *= changed feeding strategy few days before observation, PV=
Planosol/Vertisol, NF= Nitisol/Ferralsol, Tryps= trypanosomiasis
3.6.2 Statistical analysis
3.6.2.1 Influence of management on mineral concentrations in plasma
An independent t-test was conducted to evaluate the impact of communal grazing and herd size on
mineral concentrations in plasma. No significant differences were calculated.
Pearson correlations were calculated to evaluate the impact of crop residues in diet on mineral
concentrations in plasma. The percentage of crop residues in diet was significantly correlated with the
plasma copper concentration while no correlations were determined with plasma iron, zinc or
manganese (Table 13). Proportions of poaceae and herbs in total diet were not correlated with mineral
concentrations in plasma.
Table 13: correlation % crop residues in diet and mineral concentrations in plasma
Cu Fe Zn Mn Pearson
Correlation ,517 -0,343 0,214 -0,382
P 0,04 0,194 0,427 0,145
Severely deficient
Marginally deficient High
- 38 -
A one-way ANOVA using the Tukey post hoc test and an independent t-test was conducted to detect
significant differences in plasma mineral concentrations between regions and different soil types. No
significant associations were calculated even when infected animals were excluded from statistical
analysis.
To compare mineral status of cattle grazing on wetlands with animals grazing on well drained lands,
an independent t-test was conducted. The recoded copper concentration in plasma was significantly
lower in animals grazing on wetlands (0.17 +/- 0.17) than cattle grazing on well drained lands (0.85 +/-
0.22).
3.6.2.2 Correlation between mineral content in diet and plasma
Pearson correlations between mineral content in diet and plasma were calculated. A strong trend was
detected between plasma copper values and molybdenum concentrations in diet (R = -0.472 and P =
0.065) (Figure 14). Correlations between other mineral concentrations in diet and plasma copper
levels were not significant. These results indicate molybdenum as an important factor influencing
copper plasma concentrations.
Figure 14: Pearson correlation between plasma copper levels (mg/l) and molybdenum concentrations in diet (mg/kg)
To evaluate the mutual effect of Cu, Mo, Fe, Zn and S in the diet on plasma copper, the data from
mineral concentrations in diet were recoded. The more a certain mineral contributes to the
development of copper deficiency, the more points were given to the diet (Table 14). Copper values in
diets were all marginally deficient and vary from 4.18 to 7.98 mg/kg. Because variation in copper
concentration was wide, values were divided in 2 groups. Diets between 4 and 6 mg/kg copper
received two points; diets containing more than 6 mg/kg received one point. Respectively 1, 2 and 3
points were added when molybdenum, iron or sulfur were present in marginal- and severe
antagonistic concentrations and levels above the MTC. When the copper:molybdenum ratio was
marginally or severely disbalanced, respectively 1 and 2 points were granted. Concentrations of zinc
were not included in the mutual effect analysis because all estimated zinc concentrations in diet were
not in the antagonistic range.
- 39 -
Table 14: recoded mineral concentrations in diet
Severely deficient
Marginally deficient
Marginally antagonistic
Highly antagonistic
Above the MTC
*= changed feeding strategy recently and was not included in statistical analysis when plasma minerals were evaluated
Statistical analysis showed no significant correlation between the total points of the diets and copper
concentrations in plasma. Cow 16, 17 and 19 changed feeding strategy from grazing to feeding with
crop residues few days before observation. When these animals were not included in statistical
analysis, significant correlation was present (R = -0.542* and R = 0.030). These results indicate a
mutual effect of copper shortage and molybdenum, iron and sulfur overload to the development of
copper deficiency in the region.
Diet scores were significantly higher in the PV group (6.714 +/- 0.360) compared to NF (5.083 +/-
0.260). Diets in wetlands had a higher score (7.000 +/- 0.258) than diets in well drained soils (5.080
+/- 0.239). Pearson correlations indicated higher scores were correlated with higher percentages of
cyperaceae in diet (R= 0.750, P= 0.000).
CowID Cu Mo Cu:Mo Fe Zn S Total 1 2 1 2 2 0 0 7 2 2 1 0 2 0 0 5 3 2 1 2 2 0 0 7 4 2 1 2 2 0 0 7 6 2 1 2 2 0 0 7 7 2 1 2 3 0 0 8 5 1 0 0 3 0 1 5 10 1 1 0 3 0 1 6 11 1 0 0 3 0 1 5 12 2 0 0 3 0 0 5 16* 2 1 2 1 0 0 6 17* 2 0 0 2 0 0 4 8 1 1 0 3 0 1 6 9 1 1 2 3 0 0 7 14 1 0 0 3 0 0 4 15 1 0 0 3 0 0 4 18 2 0 0 3 0 0 5 19* 2 0 0 3 0 0 5 13 1 1 0 2 0 1 5
- 41 -
4.1 Prevalence of copper deficiency
From the 53 liver samples collected at Jimma municipal abattoir, 81% had deficient copper levels,
from which 58% were in the clinically deficient range. The sample size of animals might be too small to
calculate a correct prevalence of copper deficiency in the region but these results indicate copper
shortage in cattle as a severe problem. It is very likely that copper deficiency leads to a severe loss of
production in the Gilgel Gibe Catchment.
During a survey conducted by Faye et al. (1986), copper status of cattle was evaluated in 89 locations,
spread over all Ethiopia. All severe copper deficiencies were only situated in the Rift Valley while
marginal copper deficiencies were present over the whole country. Our results show severe copper
deficiency in 47% of sampled cattle in Jimma, located outside the Rift.
Remarkable is that high iron levels in liver only occurred when copper values were deficient. Higher
amounts of copper were typically accompanied by lower iron values. Several articles are available
reporting same results (Elvehjem and Sherman, 1932; Marston et al., 1938; Dent et al., 1956). Dietary
deficiency of copper or iron leads to hypochromic anaemia (Lahey et al., 1952) and increased
concentrations of the other mineral in liver. Several theories about this mechanism are suggested. The
most popular theory explaining these results suggests that iron release is dependent on the function of
ceruloplasmin. This plasma cupro-protein is responsible for the enzymatic oxidation of Fe2+ (Osaki et
al., 1966). Some authors however do not support this theory that plasma iron is decreased in copper
deficient animals. Mice lacking ceruloplasmin were not usually anaemic and even though increased
hepatic iron levels were observed, plasma iron was in the normal range (Harris et al., 1999).
Our results show an association between deficient copper levels and higher iron levels in liver and
vice versa. Even though copper shortage leads to a decreased iron release from the liver, our results
and observations by Dermauw et al. (2009) indicates iron levels in plasma are not deficient in the
region.
4.2 Management Practices
Management practices differed significantly according to region and associated soil type. The study
area was divided in the planosol/vertisol group (PV) and the nitisol/ferralsol group (NF). PV areas were
found in lower altitudes and NF in higher regions. In wetland PV, cattle were typically held in large,
communal herds while cattle in NF grazed in smaller, individual herds. Because of the larger herds in
PV, cattle covered more distance compared to herds in NF. Cattle grazing in PV areas had a more
one-sided diet while cattle grazing on NF ingested a higher diversity in plant species.
BCS did not differ significantly between cattle herded on different soil types but tended to be lower in
communal herds. It is likely that the lower BCS is the result from higher competition between animals
in communal, large herds than in individual herds. The practice of communal- or individual herding or
- 42 -
herd size did not influence copper status. Also total covered distance and herding radius were not
correlated with copper plasma levels.
As the season progresses, higher proportions of crop residues were present in the diet. Observed
crop residues were stovers from Saccharum officinarum, Sorghum spp., Zea Mays and Pisum
sativum, leaves from Musa spp. and Ensete ventricosum and residues from Eragrostis tef and Linum
usitatissimum. Higher concentrations of crop residues in diet correlated with significant lower zinc
amounts in total diet. Also molybdenum and sulfur tended to be low when higher proportions of crop
residues were present. Higher proportions of crop residues were associated with a better copper
status. This association is probably biased since PV pastures were observed first when crop fields
were not yet harvested and thus no crop residues were present in diet of the PV group. The total
proportions of poaceae and herbs in total diet did not influence copper status.
4.3 The copper cycle in the soil-plant-cattle system
4.3.1 Summary scheme results
Figure 15: the copper cycle in the soil-plant-cattle system in the Gilgel Gibe Catchment,
Ethiopia
AIPS= Amount of Ingested Plant Species
- 43 -
4.3.2 The influence of soil-type on mineral concentrations in plants
Statistical analysis of all collected plant samples showed no significant differences between mineral
content of samples collected in PV and NF. The absence of significant differences might be the result
from unequal samples taken in PV (13) and NF (53). Also no distinction was made between samples
taken from grass-, herb-, shrub- and tree species. For these reasons, statistical analysis was not
suspected to show significant differences in trace elements.
Cynodon spp, Cyperus spp and Centella asiatica were the most dominant plant species in PV
pastures. Samples from these species were collected from both PV and NF (Table 8). Remarkable
were the lower copper- and higher molybdenum concentrations in Cynodon- and Cyperus spp.
collected in wetland PV, compared to same species collected in NF. Mineral concentrations of
Centella asiatica were similar in well drained PV and NF. These results indicate that plant species in
wetland PV might have lower copper and higher molybdenum levels than well drained soils.
The importance of mycorrhizal fungi associated with roots of plants (Taiz and Zeiger, 2002) is reduced
in organic rich wetlands. Because these fungi play a role in transporting minerals such as copper, iron
and zinc (Banfield et al., 1999) to the roots of the plants, copper is less mobile in wetlands
(Ragnarsdottir and Charlet, 2002).
Several articles confirm the increased availability of molybdenum in poorly drained soils and higher
molybdenum concentration in plants growing on these soils (Davies, 1956; Kubota et al., 1961). Peat
develops essentially under wet anaerobic conditions and has been associated with molybdenum
toxicity (Kubota, 1972).
Estimated mineral concentrations were calculated in total diet. Cattle grazing on PV ingested
significantly lower amounts of copper and higher amounts of molybdenum than cattle grazing on NF.
The presence of iron particles in plants was high in both soil types but was significantly higher in the
NF areas. Sulfur levels were adequate in all PV diets but marginal antagonistic sulfur concentrations
were found in some NF diets. Zinc concentrations did not differ significantly according to soil type.
The copper:molybdenum ratio in diet was severely out of proportion for all cattle grazing in the wetland
PV pastures. Remarkable was that the diet from cow2 who grazed on a well drained PV had an
adequate ratio. Except for one cow, all cattle in the NF areas had adequate ratios in diet. Again, these
results indicate cattle grazing in the wetland PV pastures ingest lower amounts of copper and higher
amounts of molybdenum.
Acid soils that contain high amounts of free iron oxides can remove the largest quantities of available
molybdenum from aqueous solutions (Jones, 1957; Karimian and Cox, 1978). Nitisols are well drained
soils that are rich in iron and have relative low pH (4.2-6.4) (Maskall and Thornton, 1996). This might
be an explanation for the significantly lower molybdenum content in total diet from cattle grazing in NF.
Our results indicate cattle herded on wetland PV are more likely to develop severe copper deficiency
than cattle held on NF pastures because shortage of copper and excess of molybdenum is more
distinct in wetland PV.
- 44 -
4.3.3 Mineral content of forages in the Gilgel Gibe Catchment
Of the 66 plant samples, only 17 samples had adequate copper levels. The grass family or the
Poaceae were the main component of the diet for most animals. All 24 samples from the Poaceae
were deficient for copper, 9 samples were even severely deficient. The 3 samples from the
Cyperaceae, the most common herbs in the planosols, were also deficient in copper.
Most samples taken from crop residues had a severe shortage in copper. All supplementary forages
presented by farmers were deficient in copper. Next to Mito (0.8 mg/kg), Saccharum officinarum and
bulule even had the lowest concentrations of all samples, respectively 1.7 and 1.8 mg/kg.
Highest concentrations of copper were measured in Vernonia adoensis (26.5 mg/kg), a not
determined species from Aspilia (22.6 mg/kg), Sida rhombifolia (19.5 mg/kg), Psidium guajava (19.3
mg/kg) and Ipomoea batatas (17.4 mg/kg). Because concentrations of antagonistic minerals were
quite favourable in Psidium guajava (Figure 16A) and Vernonia adoensis (Figure 16B), these plant
species might be good candidates to supplement cattle in the region. P. guajava produces the guava
fruit and is a common food source in the region. Analysis of copper content in guava fruit showed
relative low concentrations (4.61 mg/kg +/- 0.26) (Ang and Ng, 2000). The tannin-rich leaves from P.
guajava are proven to have antidiarrheic, antispasmodic, antibacterial and antifungal effects
(Sudarisman et al., 1988; Dalimartha, 2001). Possibly, tannins present in V. adoensis and P. guajava
may depress copper availability. Further research is needed to evaluate the potential of these plants in
preventing or overcoming copper deficiency.
Figure 16: candidates for copper supplementation in the Gilgel Gibe Catchment – A: Psidium
guajava (19.3 mg/kg Cu) with fruit (Forum Natura Italiana, 2011a) – B: Vernonia adoensis (26.5
mg/kg Cu) (Forum Natura Italiana, 2011b)
Iron was present in high concentrations in most samples. Concentrations far above the MTC (1000
mg/kg) were found in 19 samples with highest levels found in Persicaria nepalensis (8427 mg/kg). Of
other samples, 21 had marginal and 17 severe antagonistic levels of iron. These results were
expected since iron particles are abundant in African soils (Faye et al., 1991). The high
concentrations of iron are most likely suspected of having antagonistic interactions with absorption of
copper.
- 45 -
Marginal high concentrations of molybdenum were found in 21 samples and 3 samples had high
antagonistic levels. Remarkable were the high concentrations of molybdenum in the leaf of Ensete
ventricosum (16.60 mg/kg) and the herbal mix supplement (6.71 mg/kg). E. ventricosum (Figure 17A)
can grow up to 12 meters and 1 meter in diameter (Birmeta et al., 2002). Local farmers grow the plant
as a crop (Figure 17B) and the starchy pulp in its stem and corm serves as human staple food and is
locally known as ‘kocho’. Nurfeta et al. (2009) determined severe deficient copper amounts (2.2
mg/kg) in the leaves from E. ventricosum. Another study showed copper levels varying between 6.7
and 15.7 mg/kg (Nurfeta et al., 2008). The toxic values of molybdenum in the leaves from E.
ventricosum may form a major risk for developing severe copper deficiency in cattle.
Figure 17: A: Cow with diarrhoea and depigmentations all over the body ingesting leaves from
E. ventricosum - B: Plantation of E. ventricosum (UNCCD News, 2010)
Sulfur concentrations seem to be very variable in collected samples. Seven samples had shortage in
sulfur from which 6 samples were taken from the Poaceae. Marginal – and severe antagonistic
concentrations were shown in respectively 23 and 5 samples. Two samples from Centella asiatica,
collected at 2 different locations on different soil types had one of the highest sulfur concentrations in
all plants (0.573% and 0.431%). Other samples with sulfur levels above the MTC were Sida
tenuicorpa (0.401%) and Physalis peruviana (0.486%).
Zinc was deficient in 29 samples, from which 14 severely deficient. Generally, selenium tends to be
very low in collected plant species. Only 10 samples were in the adequate range, all others were in the
deficient range. Most samples were adequate in cobalt and manganese. Remarkable were the high
concentrations of manganese in Persea spp. (1662 mg/kg) and Sesbania sesban (1159 mg/kg).
- 46 -
4.3.4 The influence of diet on mineral status of cattle
4.3.4.1 Botanical composition
A higher amount of crop residues was correlated with higher copper status in cattle. This association
is probably not reliable since PV pastures were observed first when crop fields were not yet harvested
and thus no crop residues were present in diet of the PV group.
4.3.4.2 Mineral composition
All diets from observed cows had marginal deficient copper levels ranging from 4.10 to 7.98 mg/kg per
kg DM. African soils are abundant with iron particles in soil (Faye et al., 1991) and plant samples in
the Gilgel Gibe Catchment also had high iron concentrations. Molybdenum had antagonistic
concentrations in all PV- and some NF-pastures. Sulfur concentrations were in the marginal
antagonistic range in some NF diets while zinc was in the adequate range. Zinc was marginally
deficient in only 1 diet.
To evaluate the mutual effect of Cu, Mo, Fe, Zn and S in the diet on plasma copper, the data from
mineral concentrations in diet were recoded. The more a certain mineral contributes to the
development of copper deficiency, the more points were given to the diet (Table 14). Higher points
were associated with a lower copper status. These results indicate the mutual effect of copper,
molybdenum, iron and sulfur on copper status. Zinc was not included in the mutual effect analysis
because no antagonistic concentrations were present in total diet.
A strong trend was detected between plasma copper values and molybdenum concentrations in diet.
Correlations between other mineral concentrations in diet and plasma copper levels were not
significant. These results indicate molybdenum as an important factor influencing copper plasma
concentrations.
Ward and Spears (1997) compared the long-term effects of supplemental molybdenum with a low
copper diet on copper status. The group of steers with supplemental molybdenum had decreased
plasma copper levels. Diets low in copper that were supplemented with 5 mg/kg molybdenum per kg
DM resulted in depressed growth in heifers (Phillipo et al., 1987; Gengelbach et al, 1994). The
depressed growth was attributed to the effect of molybdenum because a control group that was
supplemented with iron did not alter growth even though copper plasma levels were depressed.
All diets had marginal copper- and high iron levels but according to our results, it seems that cattle
ingesting marginally antagonistic concentrations of molybdenum are more likely to develop severe
copper deficiency and presumably show a decreased growth.
- 47 -
4.3.5 The influence of soil-type on mineral concentrations in cattle
Diets from PV contained significant lower copper- and iron- and higher molybdenum particles than
diets from NF. At the same time higher molybdenum concentrations in diet were correlated with
decreased copper plasma levels. Consequently, statistical analysis occurred to evaluate the effect of
soil type on plasma copper concentrations. No significant differences were calculated between cattle
grazing on PV and NF.
PV pastures become wetlands in the wet season because stagnation of rain water. Because these
wetlands are not suitable to grow crops, local farmers use these areas to herd their cattle. These
wetlands are typically used as communal grazing areas where farmers from the environment leave
their cattle in the morning and return in the evening. Consequently, a large herd is formed every day
whereby the wetlands are typically overgrazed. All observed PV pastures were wetlands except
pasture2. This area was situated at some higher altitude and was well drained by a near swamp.
Statistical analysis showed significant lower plasma copper levels (recoded) in cattle grazing on these
wetlands (M= 0.17 +/- 0.17) compared to cattle herded on well drained lands (M= 0.85 +/- 0.22). Used
codes for plasma copper concentration were 2 (adequate), 1 (marginal deficient) and 0 (severely
deficient). Remarkable was the adequate copper status of cow2 that grazed on well drained PV area.
Analysis indicates cattle herded in wetlands are more likely to develop severe copper deficiency.
These results can be explained by the higher availability of molybdenum in wetlands (Davies, 1956;
Kubota et al., 1961, Mitchell, 1974). This increased availability corresponds with the observed higher
molybdenum levels in plants from PV pastures and associated wetlands. Also there was a strong
trend to lower copper plasma concentrations with higher molybdenum concentrations in diet.
The statement that cattle grazing in wetlands have more decreased copper levels also corresponds
with the observations by Dermauw et al. (2009). During this research blood samples were taken in the
Gilgel Gibe Catchment from 90 cattle from 3 regions, based on altitude. Cattle from low areas had
significantly lower copper plasma levels than cattle herded in medium and high altitude. Since PV
pastures and associated wetlands are situated in the lower parts of the valley, both studies seem
compatible. There were however significant differences in copper status between cattle grazing in
same regions. Not all PV pastures are wetlands so this might explain the differences in copper status
for the lower region.
Several report cases about copper deficiency in wetlands are available. A particular copper deficiency
syndrome, formerly called “peat scours”, was reported by Cunningham (1944). Most characteristic
symptoms of the acute form affecting dairy cattle were loss of condition, severe diarrhoea and
scouring. The symptoms occurred in cattle grazing on peat land whenever there was a flush growth of
pasture. A decreased copper status was determined in these cattle. Later, Cunningham (1950)
reported that the presence of peat scours was attributed to low copper- and higher molybdenum
concentrations in forages. Allcroft (1947), Allcroft and Parker (1949) and Henderson (1957) reported
similar cases of peat scours. The long standing use of syndromes called “peat scours” or “scouring
- 48 -
disease” to describe molybdenum induced copper deficiency, indicates that the problem was
frequently observed on wet soils.
Similar syndrome of copper deficiency on wet soils, known as “polder disease”, was described in the
Netherlands (Sjollema, 1938; Brouwer et al., 1938). High molybdenum levels were detected in the
wetland areas of the Florida Everglades (Kretschmer and Beardsley, 1956).
In the NF group, cattle were found with varying copper status from almost depleted to adequate. This
variation might be explained by the varying amounts of molybdenum in diets from NF-pastures. Local
enrichments or depletions of molybdenum can be present in parent material (Gupta, 1997). The
presence of intestinal parasites or differences in tannin content in diet may be other causes for the
varying copper status in NF areas.
4.4 Suggestions to improve copper status
Our results indicate molybdenum as an important factor influencing copper status in cattle in the Gilgel
Gibe Catchment. Molybdenum is present in higher concentrations in diets from cattle grazing on
wetlands leading to more severe shortage of copper. Because there are too many cattle in the region
and crops are usually grown on better drained areas, avoiding these wetlands is not an option for local
farmers. Since copper levels decline drastically in late pregnancy because of drainage of copper by
the foetal liver (Xin et al., 1993), it might be a good idea for pregnant cows to avoid the wetlands.
Supplementing cattle with copper sulphate or spraying copper sulphate on pastures or crops might not
be realistic due to the severe poverty of farmers in the region.
Hay-making can reduce molybdenum toxicity drastically. It was suggested that protein content and
solubility decreases when forages are dried. Consequently, less sulphide is formed in the rumen which
reduces availability of copper. When forages were harvested, the problems in “swayback” areas in the
British Isles, North Holland and South Florida disappeared (Kubota, 1975; Ward, 1978). The
harvesting of hay may be an alternative practice to utilize forages from the molybdenum rich
vegetation in the wetlands. The problem with these areas is that these lands are typically used as
communal grazing areas. Too many cattle graze these lands whereby severe overgrazing is a
common problem. The production of hay might be difficult on these overgrazed wetlands.
Because availability of molybdenum increases in wet soils, drainage of wetlands might decrease
molybdenum levels. Cow2 was the only one grazing on a well drained PV. Remarkable hereby was
the adequate copper level in plasma as the only cow grazing on PV. Because fasciolosis is also a
common problem in the region, drainage of the wetlands is likely to improve the health of livestock.
Drainage is however expensive and hard to realise in practice.
Mineral analysis of collected plant samples showed favourable concentrations in Psidium guajava and
Vernonia adoensis. Feeding these plants to cattle might improve their copper status. Ensete
ventricosum had toxic levels of molybdenum and feeding this plant is likely to have a negative
influence on cattle when given in high proportions. Further research is needed to evaluate the impact
of feeding these plants.
- 50 -
5.1 Addendum
Table 15: proportions ingested plant species by observed cows
REGION REGION 1 (1700-1800) REGION 2 (1800-2000) REGION 3 (2000-2200)
COW 1 2 3 4 6 7 5 10 11 12 16 17 8 9 14 15 18 19 13
Acanthaceae 1,2 0,5 6,0 0,7 2,6
Acanthacea spp. 2,6 Hygrophila auriculata 1,2 0,5 6,0 0,7
Anacardiaceae 3,8
Rhus glutinosa 3,8
Asteraceae 5,4 2,2 1,7 11,0 7,0 5,1 9,3 10,4 0,9 3,8 7,8 11,0 12,1 17,3 Ageratum conyzoides 1,5
Aspilia africana 3,4 0,9 2,6 Aspilia mossambicensis 4,7 3,8
Aspilia spp. 1,3 2,1 3,1 Bidens macroptera 0,7 3,9 4,2 2,6 7,6 12,2
Bidens pilosa 4,9 Bidens presentinatia 3,0
Bidens spp. 0,8 2,2 1,4 0,9 5,1 9,3 2,1 5,7 5,7 2,0 Solanecio gigas 1,7 Solanecio spp. 0,7 0,9
Vernonia adoensis 4,2
Brassicaceae 4,5 1,0 Brassica spp. 4,5 1,0
Celastraceae 1,1 2,7
Maytenus obscura 1,1 2,7
Commelinaceae 0,9 8,7 2,5 0,8 1,0 Commelina spp. 0,9 8,7 2,5 0,8 1,0
Convolvulaceae 0,9
Ipomoea batatas 0,9
Cyperaceae 50,7 31,4 42,5 39,7 43,2 41,9 3,0 7,8 7,0 2,2 17,7 11,1 7,1 6,5 4,6 1,0 1,0 Carex spp. 10,4 2,3
Cyperus (giant) 11,8 Cyperus alternifolius 8,3
Cyperus spp. 32,0 29,1 42,5 39,7 43,2 30,1 3,0 7,8 7,0 2,2 17,7 11,1 7,1 6,5 4,6 1,0 1,0
Euphorbiaceae 1,6 Phyllanthus sepialis 1,6
Lamiaceae 2,3 0,7 5,6 8,2 1,3 3,0 12,4
Plectranthus punctatus 2,1 1,3 Salvia leucantha 2,2
Satureja paradoxa 2,3 0,7 Satureja spp. 5,6 4,0 3,0 12,4
Leguminosae 1,4 8,7 9,2 0,8 1,9 3,4 9,3 1,3 1,3 11,1 10,3 19,1 18,8 3,1 14,2 1,2
Desmodium intortum 5,2 Desmodium repandum 0,7 4,7 Desmodium uncinatum 1,0
Erythrina brucei 3,1 Indigofera spicata 1,3 4,3
Pisum sativum 10,9 Senna spp. 2,3
Sesbania sesban 0,8 11,1 Trifolium spp. 1,4 6,4 9,2 0,8 1,2 3,4 8,6 1,3 10,3 13,8 3,1 14,2 1,2
Linaceae 3,9
Linum usitatissimum 3,9
Loganiaceae 8,0 Buddleja polystachya 8,0
Mackinlayaceae 3,1 14,6 3,4 5,6 3,2 24,8 15,2 7,1 3,8 7,7 0,8 9,6 1,8 1,5 5,1
Centella asiatica 3,1 14,6 3,4 5,6 3,2 24,8 15,2 7,1 3,8 7,7 0,8 9,6 1,8 1,5 5,1
- 51 -
REGION REGION 1 (1700-1800) REGION 2 (1800-2000) REGION 3 (2000-2200)
COW 1 2 3 4 6 7 5 10 11 12 16 17 8 9 14 15 18 19 13
Malvaceae 6,1 0,8 4,5 5,4 7,0 0,5 7,5 1,6 3,0 Grewia spp. 1,6
Sida rhombifolia 0,5 7,5 Sida tenuicorpa 6,1 0,8 7,0 3,0
Musaceae 2,2 2,7 Musa spp. 1,1
Ensete ventricosum 1,1 2,7
Myrtaceae 2,3 2,6 Eucalyptus camaldulensis 2,6
Psidium guajava 2,3
Oxalidaceae 2,0 Oxalis radicosa 2,0
Phytolaccaceae 2,0
Phytolocca spp. 2,0
Plantaginaceae 0,5 0,9 Plantago lanceolata 0,5 0,9
Poaceae 47,9 40,3 24,8 53,4 42,4 50,0 54,5 48,4 76,5 60,2 74,1 83,3 59,4 45,6 64,6 63,0 69,5 55,0 50,0
Andropogon gajanus 1,3 Andropogon spp. 7,0 0,7 1,3 4,2 2,5 1,7 Aristida adoensis 3,2
Botriochloa insculpta 8,8 2,1 3,1 5,3 2,5 Bracharia spp. 2,3 12,3 4,8 26,1 0,8 1,3 Cynodon spp. 30,5 6,8 21,4 39,7 28,1 29,2 35,2 37,7 20,6 4,5 11,8 29,3 18,3 18,5 10,7 3,5 7,3 Digitaria spp. 4,2 2,2 9,4 1,3 3,8 2,1 5,5 6,6
Echinochloa colona 0,8 Eleusine floccifolia 2,0 7,8 8,8 5,5 3,0
Eragrostis paniciformis 0,6 1,0 Eragrostis spp. 0,7 1,0 Eragrostis tef 0,8 7,9
Hyparrhenia hirta 11,4 Lolium temulentum 2,0
Melinis repens 7,4 6,1 Melinis spp. 25,0 7,8 1,3
Panicium coloratum 1,3 Pennisetum clandestinum 2,7 1,3 0,9 13,2 7,7 0,9 1,0 12,9 Pennisetum purpureum 12,5 7,8
Pennisetum sphacelatum 8,3 2,0 8,9 0,7 19,3 2,6 5,3 4,7 Pennisetum thunbergii 2,1 2,3 0,9 2,3 1,0 5,7 1,0 3,1 4,4 1,3 8,1 3,9 12,2
Saccharum officinarum (S) 5,3 12,5 Sacciolepsis africana 0,9 1,0 Sorghum bicolour (S) 2,6
Sorghum halepense (S) 57,4 Sporobolus spp. 4,2 5,8 2,6
Zea Mays (S) 2,3 5,3 50,0 9,3 52,1 15,0 10,9 27,6 27,3 1,0 Zea Mays (F) 10,3 5,3 4,2 7,6
Polygonaceae 1,4 2,1 3,1 4,2 5,5 6,1
Persicaria nepalensis 3,1 4,2 Persicaria spp. 1,4 2,1 3,0 2,0
Rumex nepalensis 2,5 4,1
Solanaceae 4,2 Physalis peruviana 4,2
Verbenaceae 3.8
Premna schimperi 3,8
Zygophyllaceae 0,7
Tribulus terrestris 0,7
Unknown 0,7 4,5 3,8 0,9 5,0 1,3 Lima 2,5
Matane 0,9 Mito 3,4
Tokomo 3,8 1,3 Unknown 0,7 1,1 2,5
Herbal mix supplement 10.0
S= Stover, F= Fruit
- 52 -
Table 16: mineral concentrations of plant samples collected in the Gilgel Gibe Catchment
SOIL REG Cu Zn Fe Mo Cu:Mo S Se Co Mn
(mg/kg) (mg/kg) (mg/kg) (mg/kg) (%) (µg/kg) (mg/kg) (mg/kg)
Acanthaceae
Hygrophila auriculata PV 1 11,6 60,4 1136 1,05 11,02 0,278 190 2,54 611 Anacardiaceae
Rhus glutinosa NF 2 8,4 16,1 181 0,39 21,26 0,123 70 0,19 87 Asteraceae
Aspilia mossambicensis PV 1 11,2 45,8 1112 1,15 9,80 0,287 62 1,45 480 Aspilia spp. NF 2 22,6 39,9 301 0,33 69,00 0,304 82 0,37 180 Aspilia africana NF 3 8,1 34,4 1491 0,48 16,80 0,293 167 1,07 101 Bidens macroptera NF 2 5,4 27,1 540 0,34 15,91 0,272 494 0,42 63 Bidens pilosa NF 2 9,4 36,7 1551 0,83 11,42 0,203 152 1,17 117 Vernonia adoensis NF 2 26,5 34,6 302 0,47 56,38 0,276 90 0,31 132 Vernonia amygdalina NF 3 8,8 28,2 218 0,26 34,35 0,208 80 0,19 183 Celastraceae
Maytenus obscura NF 2 11,4 30,3 170 0,26 44,46 0,398 379 0,28 161 Convolvulaceae
Ipomoea batatas NF 2 17,4 21,3 617 0,35 49,64 0,360 93 0,48 226 Cyperaceae
Cyperus spp. PV 1 4,2 42,2 338 1,56 2,70 0,133 227 0,22 288 Cyperus spp. NF 3 7,8 69,1 4240 0,67 11,55 0,189 112 2,02 347 Giant Cyperus PV 1 4,6 19,7 3020 2,28 2,02 0,111 87 1,48 326 Lamiaceae
Satureja paradoxa NF 2 13,1 46,2 3300 1,05 12,49 0,381 125 2,85 269 Satureja spp. NF 3 9,7 61 947 3,90 2,48 0,286 90 0,48 119 Lauraceae
Persea spp. (avocado) NF 2 6,5 29,4 235 0,09 70,57 0,310 30 0,23 1662 Leguminosae
Desmodium uncinatum NF 2 5,2 20,7 1025 2,43 2,14 0,168 30 0,55 161 Erythrina brucei NF 2 6,0 36,7 518 0,08 74,22 0,216 70 1,03 387 Indigofera spp. NF 3 11,0 28,4 602 0,97 11,28 0,210 50 0,34 75 Pisum sativum NF 3 3,3 19 255 1,28 2,59 0,069 40 0,18 38 Senna didymobotrya PV 1 3,9 16,4 995 0,52 7,38 0,179 187 0,52 152 Sesbania sesbon PV 1 5,6 46,6 461 1,50 3,70 0,212 104 1,12 1159 Trifolium spp. NF 1 4,1 30,6 6398 0,81 5,02 0,150 170 1,15 306 Trifolium spp. NF 3 5,2 26,6 1120 2,79 1,86 0,115 86 0,84 55 Loganiaceae
Buddleja polystachya NF 2 11,3 37,4 407 2,06 5,49 0,246 200 0,50 55 Mackinlayaceae
Centella asiatica NF 1 11,1 105 1827 0,67 16,44 0,573 173 0,95 426 Centella asiatica PV 1 10,1 88,4 2809 0,76 13,36 0,431 69 1,25 752 Malvaceae
Grewia ferruginea NF 2 14,8 61,2 261 0,22 66,77 0,233 40 0,89 114 Sida rhombifolia NF 3 19,5 52 2388 1,07 18,22 0,285 70 1,19 140 Sida tenuicorpa NF 1 11,5 191 549 0,68 16,91 0,401 160 0,58 529
- 53 -
Unknown Mito NF 2 0,8 14,6 526 0,19 3,97 0,274 27 0,07 79 Supplement Bulule NF 2 1,8 21,1 189 0,17 10,59 0,089 40 0,50 55 Herbal mix supplement NF 3 8,6 52,4 1044 6,71 1,28 0,221 213 0,60 124
Severely deficient
Marginally deficient
Marginally antagonistic
Highly antagonistic
Above the MTC
Reg= Region (1= 1700-1800m, 2= 1800-2000m, 3= 2000-2200m), PV= Planosol/Vertisol, NF= Nitisol/Ferralsol, S= Stover,
MTC= Maximum Tolerable Concentration
Musaceae Ensete ventricosum NF 2 5,8 11,5 190 16,60 0,35 0,289 158 0,15 252 Musa spp. NF 2 7,0 9,04 249 0,15 47,03 0,182 76 0,15 980 Myrtaceae
Eucalyptus camaldulensis PV 1 5,1 20,9 134 0,04 115,98 0,127 102 0,23 825 Psidium guajava PV 1 19,3 31,6 210 0,65 29,55 0,228 62 0,19 151 Poaceae
Andropogon abyssinicus NF 3 4,4 34,5 295 0,19 23,37 0,137 40 0,16 101 Brachiaria spp. NF 1 4,9 59 3343 1,52 3,22 0,168 152 1,15 787 Brachiaria spp. NF 3 9,5 54,9 8026 1,78 5,36 0,224 303 3,68 299 Cynodon spp. PV 1 4,2 31,5 911 1,63 2,56 0,121 91 0,73 281 Cynodon spp. NF 2 7,1 36,4 2398 0,70 10,09 0,145 178 1,78 197 Cynodon spp. (young) PV 1 5,0 38,4 260 1,76 2,85 0,215 268 0,23 376 Hyparrhenia hirta PV 1 3,8 37,7 351 0,24 15,87 0,079 36 0,31 145 Melinis repens NF 3 5,3 31,5 259 2,63 2,01 0,244 90 0,15 90 Melinis spp. NF 3 3,4 28,8 166 1,48 2,29 0,148 70 0,15 71 Panicium coloratum NF 2 6,6 18,9 339 0,74 8,88 0,162 60 0,27 224 Pennisetum clandestinum NF 3 6,6 42,5 774 0,84 7,83 0,248 167 0,49 118 Pennisetum purpureum NF 3 9,3 40,5 391 1,88 4,91 0,149 60 0,32 43 Pennisetum sphacelatum NF 2 5,5 16,9 749 0,32 17,06 0,115 77 0,62 103 Pennisetum sphacelatum NF 3 3,1 18,4 280 0,65 4,81 0,069 134 0,13 111 Pennisetum sphacelatum NF 3 6,0 28 404 0,65 9,28 0,121 250 0,26 85 Pennisetum thunbergii NF 1 5,3 31,9 956 0,21 25,13 0,163 39 0,50 179 Pennisetum thunbergii NF 3 4,7 21,6 655 1,00 4,71 0,117 100 0,39 268 Saccharum officinarum (S) NF 2 3,4 13,6 322 0,08 45,05 0,170 58 0,15 128 Saccharum officinarum (S) NF 3 1,7 5,51 94 0,06 27,38 0,027 380 0,04 46 Sorghum bicolour NF 2 4,3 21,5 285 0,15 29,03 0,131 39 0,18 60 Sorghum halepense PV 2 3,3 28,2 255 1,66 2,01 0,124 160 0,54 393 Zea Mays (S) NF 2 2,9 10,6 205 0,34 8,45 0,077 10 0,12 65 Zea Mays (vrucht) NF 1 1,8 31,7 631 0,18 10,11 0,123 71 0,33 30 Zea Mays (S) NF 2 3,7 23,9 1015 0,27 13,76 0,066 69 1,00 97 Polygonaceae
Persicaria nepalensis NF 3 5,2 42,5 8427 1,70 3,03 0,155 223 4,09 513 Rubiaceae
Coffee leaf NF 2 11,1 7,63 282 0,26 42,64 0,212 20 0,17 114 Solanaceae
Physalis peruviana NF 2 11,4 29,8 196 0,64 17,81 0,486 90 0,33 113 Verbenaceae
Premna schimperi NF 2 5,8 63,6 150 1,06 5,53 0,164 30 0,22 172
- 54 -
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