Phosphorus (together with calcium) is a structural component for the bones, teeth and scales. In addition, it plays a role in several metabolic processes. Reduced growth rate, reduced feed efficiency and bone deformities are the most common signs of (digestible) phosphorus deficiency.

Phosphorus metabolism and requirementsDietary phosphorus (P) requirements vary widely between 0.3% and 0.9% for different fish species (Lall, 2002) and there are some indications that fish with scales have a higher P requirement than those without. In addition, the range of phosphorus requirements for salmonids is quite wide at 0.5% to 0.8% of the diet (NRC, 1993).

According to Sugiura et al (2000), for rainbow trout the P requirements are 0.66% and 0.55% for 200g and 400g fish respectively. Rodehutscord

(1996) advised a range of digestible P content in the diet of 0.24 to 0.59% for rainbow trout.

Requirements are normally expressed as net requirements or as amounts of digestible/available P. Therefore, the total P content of salmonid diets will be higher, depending on the P digestibility of the feed materials used (Figure 1).

Phosphorus sourcesFeed materials (fish meals, animal meals and plant feed materials) are the main sources of P in diets for salmonids. The P availability (or preferably expressed as digestibility) of these sources, however, does differ.

In general, vegetal feed materials (soya, cereals, etc.) have a low P digestibility because most of the P is bound to phytic acid, rendering it unavailable to the fish.

F e e d i n g r e d i e n t s n e w s f r o m A l i p h o s November 2012

The role of phosphorus in the nutrition of salmonidsMinerals are essential to fish nutrition. To cover their requirement, fish can obtain most of these (calcium, sodium, potassium) directly from the water. Phosphorus, however, is one essential mineral that has to be supplied via the diet.

Special aquaculture issue

Digestibility of selected inorganic feed phosphates

in rainbow trout p3

Aliphos feed phosphates and shrimp (Litopenaeus

vannamei) p4

Excellent results for Windmill Monamphos® in a new trial

with trout p5

Economics of feed phosphates p6

Aliphos® Windmill

FEED

Figure 1: Phosphorus metabolism, Haddock (Roy et al., 2004)

Aquatic Asia will be organized in the BITEC Convention Center in Bangkok, Thailand from March 13-15, co-located with VIV Asia 2013.

Asia is the world market leader in aquaculture, certainly in production of shrimp, crustaceans and several fish species. Aliphos will, therefore, be present at Aquatic Asia 2013. You can find Aliphos in Hall 106 at Booth A014.

Aliphos will present our “Blue Line”, our new range of products especially developed for aquaculture. We will be very pleased to welcome you at our stand to discuss products such as:

• Windmill Monamphos®, the mineral feed phosphate with superior phosphorus digestibility

• AliGlys® trace minerals, pure bis-glycinates with enhanced bio-availability

• Aliphos ButyForm, , a micro-encapsulated mixture of sodium butyrate and sodium formate to improve intestinal health and digestibility.

More information about the event can be found at the website: www.aquatic-asia.net

See you in Bangkok!

Aliphos present at Aquatic Asia 2013

Dietary intake: 1.0% P

Gut

Faeces: 0.23% P

Bone and soft tissue: 0.36% P

Phosphorus pool: 0.19% P

Kidney

Urine: 0.22%

Absorption

Re-absorption Excretion

Absorption Formation

Secretion

cont. page 2

Aliphos® Windmill

The role of phosphorus in the nutrition of salmonids (cont.)Fishmeals vary both in total and digestible P content, mainly depending on the origin and the processing of the fishmeal. High levels of fish bone lowers the P digestibility (Table 1).

Phosphates in fish feedsIf feeds for salmonids are produced using high levels of fishmeal, no (or only a limited) additional supply of P via use of inorganic feed phosphates is necessary. However, producers are increasingly using plant feed materials with both a low total and digestible P content. With these feeds, an additional supply of inorganic feed phosphates is certainly necessary.

Fish feeds are very concentrated both in energy and protein content, therefore a highly concentrated inorganic P source is the product of choice (Table 2).

Inorganic feed phosphates contain both a high level of total and digestible P. The digestibility of the different phosphates is however not the same, as it appears that digestibility greatly depends on product solubility.

The P digestibility (availability) of feeds can be measured using different indirect parameters such as growth rate and bone parameters (i.e. % P, % bone ash). The direct measurement of the apparent absorption of dietary P from the intestinal tract (apparent digestibility) is, however, the preferred method because it simply measures the difference between ingested and excreted P.

Purified diets (casein-gelatine based) fortified with amino acids, vitamins and minerals (excluding the mineral to be tested) are used in these trials (Nutrient requirements of fish, 1993). In general, P absorption is higher in salmonids than in stomachless fish.

In addition, it seems that the P digestibility of different inorganic feed phosphates increases with increasing solubility, with monobasic phosphates having a higher digestibility than dibasic or tribasic phosphates.

The role of calciumCalcium (Ca) is absorbed from the surrounding water by the gills. It is, therefore, difficult to control the total Ca intake in requirement or digestibility studies. Since fish are capable of absorbing sufficient amounts of Ca from the surrounding water, normally no additional Ca has to be supplied via the feed.

However, calcium is present in almost all feed ingredients. Therefore, attention should be paid to the Ca/P ratio in the feed. A ratio that is too wide can affect the P digestibility of the feed through the formation of indigestible Ca phosphates in the intestinal track due to the increase in pH there after passing through the stomach.

Therefore, if an additional supply of P is needed, Ca-free feed phosphates or feed phosphates with a Ca/P ratio of below 1 are preferred.

Table 2: Aliphos inorganic feed phosphates

Phosphate P% Ca% N% Mg%

MCP Aliphos Monocal 22.7 22.9 16.65 -

MDCP Aliphos Modical 21.8 21.9 20.5 -

DCP 2H2O Aliphos Dical 18 18.2 24 - -

DCP 0H2O Windmill Dicalphos 20.2 27 - -

MAP Windmill Monamphos 26 - 11 -

MgP Windmill Magnumphos 14 - - 26

Table 1: P levels and apparent P digestibility coefficients (ADC) for

rainbow trout for some selected feed materials

Feed material Total P (%) ADC - P (%)

Herring meal 2.2 45 - 52

Menhaden meal 3.5 36

Poultry meal 2.2 48 - 62

Meat and bone meal 5.6 27

Blood meal 0.7 >95

Feather meal 0.75 - 1.26 62 - 79

Wheat gluten 0.2 75

Wheat middlings 1.3 55

Corn gluten 0.5 8.5

Source: Sugiura & Hardy, 2000.

Conclusion If feed for salmonids has to be supplemented with an inorganic feed phosphate, preferably it should contain both a high level of total and digestible phosphorus. Because of the role of calcium in fish, calcium-free or phosphates with an adverse Ca/P ratio are preferred.

Aliphos® Windmill

The role of phosphorus in the nutrition of salmonids (cont.)

Digestibility of selected inorganic feed phosphates in rainbow trout Tessenderlo Group carried out an experiment into the digestibility of different feed phosphates in rainbow trout (Oncorhynchus mykiss) in 2004. The trial was conducted in cooperation with Plymouth University’s Fish Nutrition Unit in the United Kingdom.

In total, 456 rainbow trout (80g) were used at a stocking rate of 38 fish per tank, with two tanks per trial feed. Each tank had a controlled recirculation system with water temperature at 15°C and a photo period of 14 hours light and 10 hours darkness was employed.

The trial feed formulations contained digestible phosphorus (dP) levels below requirements at a level of 5g/kg, using purified reference diets as shown in Table 1 above. The P content of the casein appeared to be higher than anticipated, therefore the level of digestible P was calculated at 6.3g/kg. Calcium (Ca) levels were balanced at 1%. Yttrium oxide was used as an indigestible marker for calculation of the P digestibility.

Six trial diets were tested. In addition to a negative control, diets included Aliphos® Dical (DCP 18), Windmill Dicalphos® (DCP 20), Aliphos® Modical

(MDCP), Aliphos® Monocal (MCP) and Windmill Monamphos® (MAP). The P-digestibilities of the different feed phosphates were assumed to be 70% for Aliphos® Dical, 65% for Windmill Dicalphos®, 90% for Aliphos® Monocal, 80%

for Aliphos® Modical and 95% for Windmill Monamphos®. The P-digestibility for casein was assumed to be 90%.

The stripping technique (Austreng, 1978) was used for faecal collection. After an acclimatisation period

of three weeks, material was collected from each fish and pooled for each tank for three separate stripping periods. Diets and faecal samples were analysed for P, Ca and yttrium content, including proximate analysis (Table 1).

Trial resultsThe results of the trial showed that there were appreciable differences between the assumed P digestibility of different feed phosphates among salmonids.

Windmill Monamphos® reached a value of 86% digestible P, followed by Aliphos® Monocal and Aliphos® Modical both with values of 56%. Aliphos® Dical and Windmill Dicalphos® showed the lowest P-digestibilities at 17% and 31% respectively.

The results of the trial are in accordance with findings in previous trials with salmonids, with divalent inorganic P sources having lower digestibility values and monovalent inorganic feed phosphates demonstrating elevated coefficients that are clearly affected by their increased solubility.

Table 1: Diet composition and analysis

Ingredient (g/kg) Control DCP18 DCP20 MDCP MCP MAP

Casein 475 475 475 475 475 475

Fish oil 150 150 150 150 150 150

Crab extract 1 1 1 1 1 1

Vegetable oil 50 50 50 50 50 50

Corn starch 200 200 200 200 200 200

Dextrin 73.1 62.5 65.2 63.2 63.7 58.5

Vitamin premix 5 5 5 5 5 5

Mineral premix 20 20 20 20 20 20

Yttrium oxide 0.2 0.2 0.2 0.2 0.2 0.2

CaCO3 25.7 7.8 6.0 18.0 14.7 25.7

Aliphos® Dical - 27.48 - - - -

Windmill Dicalphos® - - 27.62 - - -

Aliphos® Monocal - - - 17.55 - -

Aliphos® Modical - - - - 20.41 -

Windmill Monamphos® - - - - - 14.61

Analysis (g/kg)

Protein 404.6 423.1 425.4 426.2 423.3 436.7

Lipid 197.8 199.9 200.1 194.8 197.7 202.0

Moisture 88.3 91.8 91.3 94.4 100.1 97.8

Ash 22.5 34.5 33.5 31.0 29.7 32.2

Phosphorus 3.6 8.5 8.3 7.7 8.8 7.4

Calcium 9.4 9.7 9.7 10.6 10.5 9.7

Yttrium (ppm) 136 143 139 158 141 145

Aliphos® Windmill

ConclusionIf a salmonid feed needs to be supplemented with an inorganic P source, preferably this should contain both a high level of total and digestible phosphorus. Because fish are capable of absorbing Ca from the water, Ca-free, or phosphates with an adverse Ca/P ratio, are preferred.

Windmill Monamphos® contains the highest level of P among commercially available feed phosphates and has a very high P digestibility (86% in the trial). In addition, Windmill Monamphos® does not contain Ca. Windmill Monamphos® is clearly, therefore, the product of choice for the production of salmonid feeds.

Vegetal feed materials contain low and variable levels of phosphorus (P) and generally have a low phosphorus digestibility (dP). It is essential, therefore, that diets are supplemented with additional phosphorus in the form of inorganic feed phosphates.

A complicating factor is that P requirements for many aquaculture species, especially shrimp, are not fully understood. Most importantly, the phosphorus digestibility in shrimp of different inorganic feed phosphates is unknown.

Tessenderlo Group, therefore, carried out a trial with shrimp (Litopenaeus Vannamei) in cooperation with INVE Technologies (Belgium) and Caditec Testing (Spain) at the Brackishwater Aquacultural Development Centre (Indonesia).

From an earlier trial with rainbow trout (Oncorhynchus mykiss), it was known that feed grade monoammonium phosphate (MAP FG) had the highest dP-content of the feed phosphates tested. MAP FG was therefore compared for growth and feed utilization by L. vannamei in a practical low phosphorus diet with monocalcium phosphate (MCP), which in trials has been shown to have high phosphorus digestibility among all animal species.

Material and methodsA basal diet low in phosphorus (reduced fishmeal) was formulated to contain 36.5% protein and 5.2% fat. Graded levels of MCP (22.7% P) and MAP FG (26% P) were used (table 1). In the first part of the trial the diets were fed in triplicate to L. vannamei (1.20 ± 0.01g) for 4 weeks. After this preliminary trial two treatments (Control and MAP FG 1.8) were extended for another 6 weeks.

ResultsGrowth and feed utilization were improved by 9% and 11%, respectively with the MCP 2.5 diet compared to the Control. With MAP FG 1.8

this effect was even more obvious giving an improvement of 13% and 15% respectively (see Fig 1). This indicates that with the same amount of P in the diet but with a higher bioavailability, better growth and feed utilization is obtained.

During the extended trial the shrimps fed the control diet reached 7.94 ± 0.35g in 10 weeks whereas those fed the MAP FG 1.8 treatment reached 8.85 ± 0.35g and the feed conversion improved by 7%.

Aliphos feed phosphates and shrimp (Litopenaeus vannamei)Fishmeal is becoming a limited and expensive resource. Diets for aquaculture species are therefore changing. This has resulted in diets being formulated using increasing levels of vegetal feed materials.

Table 1: Experimental treatments* and their phosphorus (P) content

Treatment P (%)

Control 0.73

MCP 1.0 0.93

MCP 2.5 1.23

MAP FG 0.75 0.91

MAP FG 1.8 1.16

* The MCP used is especially developed for aquaculture application and has a powdered structure while the MAP is a special Feed Grade MAP also with a powdered structure.

Aliphos® Windmill

ConclusionThe study showed that P supplementation improves growth and feed utilization in shrimps fed practical feed formulations and that feed grade monoammonium phosphate is an effective source of phosphorus for Litopenaeus vannamei.

Fig 1: Shrimp; Specific growth rate (SGR - left scale) and feed conversion

(FCR - right scale) after 4 weeks.

Experimental tank system at BADC Institute, Jepara, Indonesia.

Excellent results for Windmill Monamphos® in a new trial with trout In aquaculture it’s also important to know the bio-availability, or digestibility, of feed ingredients including feed phosphates. Aliphos has already carried out trials on both trout and shrimp to study these properties for its feed phosphates (see this newsletter, Newsletter #3, April 2005 and Newsletter #7, June 2007). The new trial below shows that Windmill Monamphos® - a feed grade monoammonium phosphate - has a superior P-retainability and P-digestibility with trout.

Aliphos commissioned the new trial with trout investigating the bio-availability of three of its feed phosphates in 2011. The trial was carried out by Imares-WUR in The Netherlands. Its aim was to evaluate the P-digestibility and P-retention of three different types of feed phosphate, confirming and reinforcing the results of the earlier Plymouth trial.

Trial set-upThe trial was conducted at the Aquaculture and Fisheries Group (AFI) in Wageningen using a recirculation system with 12 tanks and 15 fish. The trout were fed four different diets: one low P control (D0) and three trial diets containing the feed phosphates Aliphos® Dical (DCP), Aliphos® Monocal (MCP) and Windmill Monamphos® (MAP).

The diets were based on casein and other low P-content feed materials to enable the highest possible inclusion of the feed phosphates. Diets were formulated according to NRC (1993) recommendations.

The P-content of the D0 control diet was only 3.5 g P/kg, while the trial diets were formulated to contain 6.4 g total P/kg and a standardised Ca content of 10 g/kg. Yttrium oxide was included for the calculation of the P-digestibility. The trial consisted of an acclimatisation period of 10 days

followed by an experimentation period of 41 days during which the fish were hand fed at a rate of 12 g/kg0.8/d.

Sampling and analysisThe fish were weighed at the start and finish of the experiment to calculate their growth. Feed intake was recorded daily and pooled samples of feed were analysed.

The P-retention rate was calculated by proximate analysis, using 2 x 10 fish at the start of the trial and 12 x 7 fish at the end. Faecal samples were collected once every week, four times in total, and used to calculate P-digestibility by means of stripping.

ResultsThe feed analysis is given in Table 1, while Table 2 presents the feed (FI), nitrogen (NI) and phosphorus (PI) intakes.

Trout fed the diet containing MAP showed the greatest growth, followed by those fed the MCP and DCP diets (Fig. 1). There were also small differences in FCR; the MAP diet showing the lowest level and the D0 diet the highest (Fig. 2).

Based on analysis of the trout, the trout feed and feed intake, P-retention values were calculated. There were large differences between the different P-sources: Aliphos® Dical 55.7%, Aliphos® Monocal 68.0% and Windmill Monamphos® 92.2% (Fig. 3).

Table 1: Feed composition

Diet (%) Dm (%) Cr-Prot (%) Ether-Ex. (%) Ash (%) P (%) Ca (%)

D0 95.9 41.9 22.6 3.6 0.35 0.98

MCP 95.2 41.9 22.4 4.1 0.68 1

DCP 94.5 42 22.3 4.1 0.69 1

MAP 95.3 44.4 22.5 4.2 0.69 0.96

Table 2: Feed, nitrogen and phosphorus intake

Diet FI NI PI (g/kg0.8/d)

D0 9.5 0.64 0.033

MCP 9.3 0.63 0.063

DCP 9.2 0.62 0.063

MAP 9.2 0.65 0.063

Fig. 1: Growth (g/day)

Fig. 2: FCR

Fig. 4: dP strip (%)

Fig. 3: P-retention (%)

Aliphos® Windmill Aliphos® Windmill

cont. page 6

More information on the Aliphos Blue Line can be found at: www.aliphos.com

Troonstraat 130, B-1050 Brussels, BelgiumTel: +32 2 639 1858 Fax: +32 2 639 1713

www.aliphos.comanimalnutrition@aliphos.com

dP content of different IFPs (dP%)

ConclusionTrout fed Windmill Monamphos® displayed the highest growth and the lowest FCR. They also showed the highest P-retention (92%) and P-digestibility (90%).

AdviceBased on the outcome of this study and the earlier Plymouth study, Aliphos advises that the P-digestibility figures below for the different feed phosphates be used in diets for salmonids.

Excellent results for Windmill Monamphos® (cont.)

P-digestibility differed significantly between the different P-sources (Fig. 4). Aliphos® Dical (DCP) showed the lowest value, followed by Aliphos® Monocal (MCP). Windmill Monamphos® (MAP) had the highest value (90%).

The economics of feed phosphatesCalculation of the cost price of feed phosphates should be primarily based on digestible P (dP) content - the only objective criterion.

Assuming the following starting points:

Aliphos® Monocal cost = 100 units, based on P content = 22.7%; dP = 70% -> dP content = 15.9%

What is the value of Windmill Monamphos®?

P content = 26%; dP = 90% -> dP content = 23.4%Therefore, Windmill Monamphos® value = 147 units.

ConclusionWe can conclude that based both on the high total P-content and high level of digestible P, Windmill Monamphos® is the most economical phosphorus source for use with aqua cultural species.

Fig. 2: Value/dP content of different feed phosphates (units)

Aliphos® Windmill Monocal Monamphos®

P Content 22.7% 26%

dP 70% 90%

dP content 15.9% 23.4%

Fig. 1: P and dP content of different feed phosphates (%)

P content dP content

Overall conclusions• Windmill Monamphos® has the highest digestible phosphorus

content of all tested inorganic feed phosphates; as a consequence the excretion of P in the aquatic environment is the lowest.

• Windmill Monamphos® is more than 98% water soluble with a superior P-digestibility of 90% in shrimps and fish, making it the preferred source of mineral P for aquaculture feeds.

• Windmill Monamphos® has the highest phosphorus content of all feed phosphates available on the market. Together with a proven high phosphorus digestibility, this makes it the product of choice for the production of highly concentrated feeds, especially those for fish.

• Above all, Windmill Monamphos® is the most economicfeed phosphate for use in aquaculture.