Animal nutrition (Compiled by Austine Mabika)

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ANIMAL NUTRITION

(Compiled by Austine Mabika) Anatomy and Physiology of Digestion (An Overview) The gastro-intestinal tract (GIT) is vitally important to the animal because it is made up of organs that responsible for the utilisation of feeds and nutrients. Therefore some knowledge of its anatomy and physiology is necessary for evaluating feedstuffs and formulation of diets. In addition many feed related factors may alter normal functioning of the GIT. Some degree of familiarity with anatomy and physiology are important for a reasonable understanding of practices and problems in feeding livestock. The digestive system consists tube extending from the mouth to the anus. Its functions are:- - ingestion - grinding - digestion - absorption of food - elimination of solid wastes The digestive system reduces the nutrients in the food to compounds that are simple enough to be absorbed and used for energy and building other compounds for metabolic use. Portions of the digestive tract are the mouth, pharynx, oesophagus (forestomach in ruminants), glandular stomach, small intestine, large intestine and the accessory glands, which are the salivary glands, the liver and the pancreas. Animals are divided into 1 (non-ruminants) and ruminants. 4 have a simple stomach Ruminants have a four-compartmented stomach, such that it chews the cud while ruminating The Mouth Functions of the oral cavity (mouth) and associated structures include prehension, mastication, insalivation and bolus formation, as a defensive and offensive weapon. In the ruminant, saliva, secreted into the mouth, functions to maintain the fluid consistency of the rumen contents, helps neutralize acids formed by rumen organisms and may help prevent frothing. The Oesophagus The oesophagus is a direct continuation of the pharynx. It is a muscular tube extending from the pharynx to the stomach just caudal to the diaphragm. Food passes down the oesophagus into the stomach. Non-ruminant Stomach Found in chickens, pigs. The stomach is the shape of a bent pear and has the cardiac sphincter at its entrance and the pyloric sphincter at its exit. The glandular surface area of the stomach is increased many times by infolding of the epithelium into depressions called gastric pits.

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The Ruminant Stomach Rumination is a process that permits an animal to forage and ingest food rapidly, then complete the chewing at a later time. It involves regurgitation of the food (returning it to the mouth), remastication (rechewing), reinsalivation (mixing with saliva) and finally reswallowing of the food. The stomach of a ruminant has 4 chambers,When the cow first chews and swallows a mouthful of grass, boluses enter both the rumen and the reticulum, where symbiotic bacteria go to work on the cellulose-rich meal. As by-products of their metabolism, the bacteria secrete fatty acids. The cow periodically regurgitates and rechews the cud, which further breaks down the fibres, making them more accessible to further bacterial action. The cow then reswallows the cud, which moves to the omasum, where water is removed. The cud, containing great numbers of bacteria, finally passes to the abomasum for digestion by the cow’s own enzymes. Because of the bacterial action, the diet from which a ruminant actually absorbs its nutrients is much richer than the grass the animal originally ate. In fact, a ruminant eating grass or hay obtains many of its nutrients by digesting the symbiotic bacteria, which reproduce rapidly enough in the rumen to maintain a stable population. The rumen, reticulum, and omasum of ruminants are collectively known as the forestomach. Reticulum Also called the honeycomb, and as the names imply, it is lined with mucous membrane containing many intersecting ridges which subdivide the surface into honeycomb-like compartments. The location of the reticulum immediately behind the diaphragm places it almost in apposition to the heart, so any foreign objects such as wire or nails that may be swallowed tend to lodge in the reticulum and are in a good position to penetrate the heart. The Rumen The rumen is a large muscular sac that extends from the diaphragm to the pelvis and almost entirely fills the left side of the abdominal cavity. The Omasum The omasum is a spherical organ filled with muscular laminae that descend from the dorsum or roof. The mucous membrane covering the laminae is studded with short, blunt papillae that grind roughage before it enters the abomasum (true stomach). The Abomasum The abomasum (true stomach) is the first glandular portion of the ruminant digestive system. The Small Intestine The small intestine is divided into three parts:- - the duodenum - the jejunum - the ileum The common bile duct from the liver and the pancreatic duct from the pancreas enter the duodenum a short distance behind the pylorus. Surface area of the mucous membrane lining the intestine is increased by circular folds and by villi, both of which project into the lumen of the intestine.




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The Large Intestine The large intestine consists of the caecum, which is a blind sac, and the colon, which consists of ascending, transverse and descending parts. The descending colon terminates as the rectum and anus. There is considerably more variation in the large intestine (particularly the ascending colon) from one species to another than in the small intestine. The horse has the largest and most complex large intestine of any of the domestic animals. Accessory Digestive Organs There is much similarity from one species to another in the glands that aid digestion. In addition to the numerous small glands located in the walls of the stomach and intestine, accessory glands include the salivary glands, the liver and the pancreas. Basic Animal Nutrition Feeds take the greatest proportion of running costs of any livestock enterprise. Efficiency in the feeding is therefore essential and an understanding of feeds, their evaluation and utilisation is necessary. Metabolism A sequence of chemical processes that take place in a living organism. Some processes involve degradation of complex compounds into simpler substances while others involve synthesis of complex compounds from simple substances. Waste products are also produced during metabolism and these have to be chemically transformed before being ultimately excreted. Such transformation also form part of general metabolism All changes that take place in nutrients after they are absorbed from digestive tract. Succession of chemical processes that take place in a living organism. Involves catabolism or anabolism. Catabolism The conversion or breaking down of complex substances into simpler materials or compounds. Destructive metabolism. Anabolism Anabolism is the conversion of simple substances into more complex substances. Constructive metabolism. Food- refers generally edible material that can be consumed by animal. Food for farm animals can be divided into 2 groups i.e. Roughages and Concentrates; these assume different usefulness depending on whether the animal is a ruminant or a non-ruminant Nutrient- any food constituent or chemical substance that can be used for maintenance, production and the health of the animal e.g. Carbohydrates, fats, proteins, minerals, vitamins, water, amino acids. The Functions of Food 1. The mammalian body needs heat and energy to function normally.




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2. Nutrients are required for the repair of worn out tissues. 3. Nutrients are required for the body to increase in weight and size. 4. Food supplies nutrients for the production of offspring. 5. Production of meat, milk, wool etc. Is dependent on the supply of food. 1, 2 and 3 = Maintenance requirement 4 and 5 = Production requirement Total nutrient requirement = Maintenance + Production requirement. Main Components of Feed Six Fractions of a Feed Sample as Analyzed by the Weende Method

Fraction Components

1. Moisture Water and volatile acids and bases 2. Ash Essential and non-essential elements

(Minerals) Major: Ca, P, Mg, K, Na, Cl, S Trace: Fe, Mn, Cu, Co, I, Zn, Mo, Se

3. Crude Protein Proteins, amino acids, amine B-vitamins, nitrates, nucleic acids

4. Ether Extract Fats, oils, waxes, fat soluble vitamins (A, D, E, K) Pigments

5. Crude Fibre Cellulose, hemicellulose, lignin 6. Nitrogen-free Extract Cellulose, hemicellulose, lignin, sugars,

Starch, fructans, water-soluble vitamins WATER Water is one of most important feedstuffs but one that is often overlooked. Water makes up 70% of the body of an animal. The body can loose all of its fat, 50% of its protein and still survive but loss of only 10% of its water will result in death. Three sources:

1. From food 2. Drinking water 3. Metabolic water- water is by product of many chemical reactions in the body.

Functions in animal body: 1) Solvent, transports nutrients within body 2) Medium in which waste products excreted 3) Chemical reactions brought about by enzymes take place in solution 4) Absorbs the heat of heat producing reactions with a minimum in body temperature 5) Regulates body temperature by the evaporation of water in the lunes and on the skin 6) Synovial fluid, lubricant in the joints 7) Cerebro-spinal fluid, water cushion for N.S. 8) Ear conducts sound, eye concerned with sight 9) Embryo surrounded by water absorb shock 10) Maintaining cell turgidity




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Water intake. Several factors affect level of water intake by an animal in a day Food intake – Dry matter intake increases water requirements Dietary composition – A high protein diet requires more water because excretion of urine is

associated with N content of diet. Climatic conditions – hot, warm less humid conditions increase water intake Physiological state – Dairy cows require more water with high producing dairy cows in

excess of 100l of water per day. Pregnant cows also need more water. Dry Matter This is the part that satisfies the nutrient requirements of animal for energy, proteins, vitamins and minerals. Organic and Inorganic Matter. However there is no such sharp distinction as many organic compounds contain inorganic elements Organic matter Carbohydrates (CHO) Made up of carbon, hydrogen and oxygen. Important source of energy (75% of all dry matter in plants used as feed). CHO in animal stored in liver and muscles as glycogen and as dissolved sugars (glucose) in blood. Excess CHO stored as fat. Range from simple sugars to highly complex compounds (non-sugars.) Sugars Monosaccharides e.g. glucose, fructose, galactose Glucose and Fructose are the most common simple sugars in feed and feed ingredients. They occur as simple sugars in both plant and animal tissue, but only in small quantities. Fructose is converted readily to glucose in animals so it is available to body metabolism as glucose. Other simple sugars are present in feed but in very small quantities. Disaccharides, e.g. sucrose (glucose + fructose), lactose (glucose + galactose), maltose (glucose + glucose) These are present in plant tissue in larger quantities than simple sugars. Sucrose is found in high concentrations in plants such as sugar cane and sugar beet. Lactose is found only in milk Non-sugars These are all polysaccharides e.g. starch, glycogen, cellulose, hemicellulose Important polysaccharides: Starch Starch is the most important polysaccharide of non-fibrous nature found in plants, found particularly in grains and tubers. It is composed of units of glucose. Starch hydrolysed to dextrin, maltose and glucose. Glycogen CHO reserve in liver and muscles of animals. It is the main carbohydrate storage in animals Essential part energy metabolism. Cellulose




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Most abundant plant constituent, forming the fundamental structure in plant cell walls. Bacteria break it down into glucose, enzymes from the animal cannot break it down and this makes it less digestible than starch. Hemicellulose Composed of glucose, galactose, arabinose, xylose units joined together. More digestible than cellulose (leafy and woody structures). Closely associated with cellulose. Lignin It is not a carbohydrate. It is a long chain polymer (similar to some plastics) that exists as a structural component in plant tissues. Gives chemical and biological resistance to cell wall and mechanical strength to the plant. Causes cellulose to be tough (stalks and stems plants). As plants age they become lignified. It is of particular interest to animal nutrition because of its high resistance to chemical degradation. Physical incrustation of plant fibres by lignin renders them inaccessible to enzymes that normally digest them. Strong chemical bonds exist between lignin and many plant polysaccharides and cell wall protein, which renders these compounds unavailable for digestion. Considered indigestible for animals therefore mature hays and straws are of low digestibility. Function of energy Construction body tissues. Synthesis of products like eggs. For work done by the animal.

Evaluation of carbohydrates Nutrients are needed for construction of body tissues and synthesis of products like milk, wool. For this to happen the animal need energy from cho to do work. In the process heat is generated. An animal firstly utilises free glucose for energy and if starved will mobilise energy from glycogen, fat and then protein. This is done through a catabolic process and if it becomes worse, the animal will lose weight (condition). The reverse is true if the animal is overfed and is done through the process of anabolism. The various sources of energy are: maize, wheat, barley, oats, coconut cake meal, rye grass, grass hay, Lucerne etc. Partition of food energy. When food is ingested, it has gross energy. After digestion, faeces are lost and what is left is called digestible energy. This is the energy in the feed and if we remove the energy that is lost through urine and methane gas production, we will be left with metabolisable energy. As the name suggests, this is the energy that goes towards metabolism. Metabolism generates heats and if this heat is removed, the energy left is called net energy. This is the energy that is actually available to the animal for its use. The use of this energy is prioritised towards maintenance. The excess energy from this is then used for production or is retained. If you measure the total heat that is produced by this conversion of feed to the last stage, it is the heat increment. This measures the total amount of energy that is needed to do work. Proteins Proteins are essential constituent of all tissues and organisms. Exist as the insoluble forms like feathers, hair, wool and hooves to highly soluble proteins such as plasma proteins. Each protein has a distinctive function in the body eg protection (hair, skin), to defence against invading microorganisms (antibodies), structural functions (muscle, tendons, hooves, cell wall) and metabolic




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functions (blood serum proteins, enzymes, hormones and immune antibodies). Proteins in the blood have an important function of maintaining plasma osmotic pressure. Composition. Composed of long chains of amino acids, some proteins contain metals eg haemoglobin contains iron and casein has phosporus. Glycoproteins contain carbohydrates and lipoproteins contain lipids. Composed carbon, oxygen, hydrogen and nitrogen. Amount of protein in an animal food equal to amount of N x 6,25. A crude basis for protein calculation. 1/5 of animal body is proteins) therefore a good supply of proteins is important!. Built up from amino acids (A.A). About 20 amino acids are needed by the animal. Plants can synthesize all of these from ammonia and nitrates. Therefore A.A must be supplied in the diet as the body cannot synthesise them (essential A.A), others produced from other A.A. (non-essential A.A). The liver is the site of synthesis of amino acids. Ruminants benefit from microbial protein synthesis, which means they don’t have absolute need for essential amino acids.

a) Animal - (Fish, blood, carcass meal) b) Plant - (Groundnut, cottonseed, linseed, soyabean oil cake) c) NPN-Bonds - (urea) d) Wastage - (chicken litter)

Essential amino acids: Lysine Tryptophan Histidine Phenylalanine Valine Leucine Iso-Leucine Threonine Arginine Methionine Non-essential amino acids: Glycine Alanine Serine Aspartic acid Glutamic acid Proline Hydroxyproline Protein Requirements. Monogastric animals and avians have an absolute need for essential amino acids. Requirements highest for young growing animals, lactating, pregnant animals and laying chickens. Requirements are lowest for adult animals on maintenance. Protein Deficiency It is manifested in animals by poor growth rates, lowered birth weights and high infant mortality, reduced milk or egg production, infertility, pot bellies and poor defence against invading pathogens.




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Practically deficiency is most noted in young rapidly growing animals, lactating animals and laying hens. Lipids Any compound soluble in ether. True fats are most important part of the group. Composed of Carbon, Hydrogen and Oxygen. Condensed reserve and source of energy. Structural elements essential for various reactions. Ordinary roughage very little fat, main source are oil seeds (cotton). Fat releases ± 2,25 times more energy on combustion than proteins and CHOs, because of a higher C and H content. Chemically they range from fats and oils to complex sterols. Nutritionally fats and oils are important and are distinguished by melting points, fats being soluble at room temperature and oils being liquid. Fats can be grouped into essential and non essential fatty acids. The essential fatty acids are linoleic and linolenic acids. Aracdonic acid is sythesised from linolenic acid and it becomes essential when dietary linolenic acid is limited. In monogastric animals the composition of body fat is determined by the dietary fats, for example giving oils to pigs will result in a body fat that is more oily and not solid. This is not true for ruminants where dietary fats undergo modification in the rumen from M/O. Fats can be protected from microbial digestion by addition of formaldehyde in the diet. Ketosis - abnormal breakdown of fats or protein for energy due to shortage of CHO. Ketone bodies result from C fragments and appear in the blood. This causes an increase in acid concentration resulting in acidosis which can lead to coma and death. This condition is responsible for acetonemia in dairy cattle and "pregnancy disease" (Domsiekte) sheep. Symptoms are high blood and urine ketone levels, low blood sugar, depleted glycogen reserve, lack of appetite and drop in yield. Treatment - glucose injection. Protein-Energy Deficiency 4. VITAMINS (Vital Amine) Organic compounds which are required in small amounts for normal growth, production reproduction and health maintenance. Functions: * structural parts of enzymes and co-enzymes. * Catalysts for enzyme systems regulate metabolism and E transfer. Can be found as provitamins or vitamin precursors. Vitamins destroyed by oxidation, which can be speeded up by heat, light and certain metals (storage) Two main groups: 1. Water soluble (B complexes, Vit. C) 2. Fat soluble (Vit. A, D, E and K) Vitamins important in animal nutrition

VITAMIN CHEMICAL NAME

Fat-soluble vitamins A Retinol




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D2 Ergocalciferol D3 Cholecalciferol E Tocopherol K Phylloquinone Water-soluble vitamins B complex B1 Thiamine B2 Riboflavin Nicotinamide B6 Pyridoxine Pantothenic acid Biotin Folacin Choline B12 Cynocobalamin C Ascorbic acid

FAT SOLUBLE VITAMINS VITAMIN A Functions Most important for growth and maintenance of cell structure - especially epithelial tissue. Found in the retina - sight. Deficiency Reduced resistance to bacterial infections of mucous membranes of lungs, eyes and reproductive organs. Results in:- 1. Night blindness - xerophthalmia. 2. Abnormal development of skeleton (in utero.) 3. Nervous symptoms in cattle, sheep and pigs. 4. More of a problem with poultry. Grazing animals have a large liver reserve - can be a problem in droughts and with ration fed animals. Sources 1. Liver is a rich source. 2. Carotene (provitamin) in plants - yellow pigment - can be converted into Vit. A.




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3. Manufactured synthetically. 4. Green plant material - destroyed by sunlight. VITAMIN D Functions Appears to facilitate deposition of Ca and P in bones. Increases absorption from the intestine of Ca and P. Deficiency 1. Young animals - Rickets - bones are weak and easily broken. Legs bowed, back arched,

swollen knees and hocks. Stiffness and paralysis. 2. Old animals - Osteomalacia - weak brittle bones from reabsorption of bone. Sources 1. Sun dried roughage and leaves of growing plants. 2. Provitamin in skin and skin secretions converted to Vit. A by sunlight. 3. Manufactured synthetically. VITAMIN E Functions Biological antioxidant (within and outside body). Combines with oxygen preventing oxidation of other vitamins. Controls tissue respiration. Deficiency 1. Young animals calves, chicks and lambs - muscular dystrophy of heart muscle - death. Skeletal muscle - stiffness and abnormal conformation. 2. Infertility in rats only. Interaction with Se with regard to most deficiency diseases. Sources 1. Widely distributed in foods - green leaves and cereal grains. Disease conditions caused by vitamin e deficiency

CONDITION ANIMAL TISSUE AFFECTED

Embryonic degeneration Sterility

Hen, ewe Cock, rat

Vascular system Male gonads

Muscular dystrophy Stiff lamb disease White muscle disease

Chick Lamb Calf, sheep, lamb

Skeletal muscle Skeletal muscle Skeletal muscle




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Necrotic liver Degeneration

Rat, pig Liver

Encephalomalacia Chick Cerebellum Exudative diathesis Rat, chick Capillary walls Blood protein Destruction

Chick Blood

Body lipid degeneration Pig, chick Depot fat oxidative Rancidity (in vivo)

Fatal syncope Pig, calf Heart muscle

VITAMIN K Functions Plays a role in blood coagulation - prevents haemorrhage. Deficiency Synthesised by M/O in rumen - deficiency in ruminants and pigs very rare. In non ruminants (chicks): 1. Haemorrhage - bird injures easily and may bleed to death. Deficiency can also result from occlusion of bile duct. Sources 1. Green leafy material. 2. Bacterial synthesis. WATER SOLUBLE VITAMINS M/O in rumen produce all these vitamins. Deficiency diseases observed with non ruminants.




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Summary of the water soluble vitamins

ANIMAL VITAMIN SYMPTOMS OF A DEFICIENCY

SOURCES

Pigs and poultry

Thiamine (Vit. B1) Poor appetite, respiratory problems and nerve degeneration

Germ of grains and green leafy crops.

Pig Chicks

Riboflavin (Vit. B2) Poor appetite, skin and eye problems. Curled toe paralysis

Green leafy crops, synthetic.

Pigs Poultry

Nicotinamide Enteritis, dermatitis and poor growth. Black tongue.

Tryptophan, Groundnuts and sunflower.

Pigs Fowls Chicks

Pyridoxine (Vit. B6) Poor appetite, anaemia Poor hatchability and egg production. Jerky movements.

Cereal grains.

Pigs Fowls Chicks

Pantothenic acid Poor growth, diarrhoea "goose stepping" gait. Poor growth, dermatitis. Poor hatchability.

Cereal grains and molasses.

Chicks Folacin Anaemia, poor growth. Intestinal bacteria. Chicks Biotin Lesions on feet. Intestinal bacteria. Pigs chicks

Choline Slow growth, fatty liver. Slipped tendon.

Cereals, green leafy crops, fats.

Young animals. Fowls Pigs

Cyanocobalamin (Vit. B12)

Poor growth. Poor hatchability. Dermatitis

Intestinal bacteria. Microbial origin in foods.

Ascorbic acid (Vit. C) Not known in farm animals. Synthesised from glucose.

Green leafy veg, citrus fruits.




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THE ESSENTIAL MINERAL ELEMENTS 1. Major elements: Calcium - Ca Phosphorus - P Potassium - K Sodium - Na Chlorine - Cl Sulphur - S Magnesium - Mg 2. Trace elements: Iron - Fe Zinc - Zn Copper - Cu Manganese - Mn Iodine - I Cobalt - Co Molybdenum - Mo Selenium - Se 3. Probably essential: Fluorine - F Bromine - Br Barium - Ba Strontium - Sr MINERALS (INORGANIC MATTER) Literature - Animal nutrition McDonald, Edwards and Greenhalgh.




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Minerals constitute about 3% of body weight and 80% of this is found in the skeleton and other hard tissues. Most minerals are supplied by forages. Other sources are drinking water and supplementation. Several factors affect the mineral content of plants i.e. the genus, species and strain of plant the season of the year or climatic conditions the soil type on which it grows the stage of maturity of the plant. The applicatioon of artificial feritilizer, mostly nitrogen. "Essential mineral elements" - Those minerals which have been proved to have a metabolic role in the body. Mineral elements divided into two groups according to the amount required and amount present in the body:- 1. Macro (Major) elements - Large quantity 0.5 - 15 gm/kg. (400 kg steer = 4 kg element) 2. Micro (Trace) elements - Small quantity. 0.1 - 80 mg/kg. (400 kg steer = 8 gm element) Functions 1. Many operate in pairs or groups with complex interactions. 2. Structural components in the body. 3. Enzyme activators. 4. Cell metabolism. MACRO ELEMENTS. CALCIUM Most abundant mineral in the body Functions 1. Structural component of bone. 2. Transmission of nerve impulses. 3. Maintains osmotic pressure. 4. Muscle contraction. 5. Coagulation of blood. Deficiency 1. Rickets. 2. Osteomalacia. 3. Milk fever. Abnormal Ca : P ratios, P or Vit D deficiency also responsible for rickets and osteomalacia. Ca : P ratio should be 1:1 to 2:1




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Sources 1. Green leafy crops (legumes). 2. Fish meal, bone meal. 3. Limestone, di and monocalcium phosphate. PHOSPHORUS Functions 1. Structural component of bone. 2. Found in cell nucleus - cell division. 3. Important component of blood. Plays a role in energy metabolism as adenosine triphosphate (ATP)




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Deficiency – Is very common in grazing animals as the content is very low on mature grass. The recommended intake is between 3 – 7 grams per day for cattle. 1. Rickets and osteomalacia. 2. "Pica" - Abnormal appetite. 3. Chronic def- stiffness and muscular weakness. 4. Prolonged def- low fertility and milk yield. Sources 1. Milk. 2. Cereal grains. Fish and bone meal. Monoclcium phosphate, dicalcium phosphate Phosphorous supplementation gas resulted in improved fertility and better growth of calves. SODIUM Functions 1. Osmotic regulation of body fluids. 2. Component of blood plasma. Deficiency 1. Retards growth. 2. Reduced utilization of proteins and energy. 3. Affects egg production. Sources 1. Carcase meal and marine foods. 2. Common salt. MAGNESIUM Functions. 1. Associated with Ca and P in the skeleton. 2. Activator of enzyme systems. 3. Important function in blood. Deficiency. 1. Hypomagnesaemic tetany of adult ruminants, nervousness, staggering, convulsions - death. Treat with Mg sulphate injection. Sources. 1. Vegetable protein concentrates. 2. Clovers. 3. Mineral supplement - magnesium oxide. MICRO ELEMENTS




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IRON Functions. 1. Component of haemoglobin (Hb)- protein involved with transport of oxygen in blood. 2. Activates enzymes. Deficiency. Anaemia especially with piglets - Fe content of milk is low. Piglets are most affected because their fast growth rate cannot match supply of the mineral in the diet. Milk is a poor source of Iron. Sources. 1. Retained when red blood cells (Hb) are catabolized. 2. Widely distributed in leafy plants and legumes. COPPER Functions. 1. Formation of blood - fixation of Fe in Hb molecule. 2. Preservation of the nervous system. 3. Pigmentation of wool and hair. 4. Maintains normal crimp. 5. Calcification of bone. 6. Maintenance of fertility. Deficiency. 1. Anaemia. 2. Degeneration of C.N.S.- Swayback in lambs and calves, difficult to treat. 3. Decolouration of wool and hair. 4. Lack of crimp in Merino wool. 5. Reproductive problems. Sources. 1. Common in most feeds. 2. Fertilize pastures with copper sulphate. 3. Copper sulphate licks. 4. Dose with copper oxide or inject. Excess copper given to animals can be toxic. COBALT Functions. 1. Required by M/O for synthesis of vit B12. 2. Required by M/O for digestion of roughage. 3. Necessary in the synthesis of Hb.




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Deficiency. 1. Anaemia 2. Weakness, emaciation, listlessness, loss of appetite and weight - death. Known as pining. Occurs on calcareous soils in the coastal areas. Sources. 1. Most foods and pastures. 2. Fertilize pastures. 3. Licks 4. Dosing and injection. IODINE Functions. Constituent of hormone thyroxine which controls metabolic rate of the body. Deficiency. 1. Goitre - enlarged thyroid gland. 2. Reproductive failure. 3. Low metabolic rate sluggishness. 4. Youthful ageing. Sources. 1. Trace amounts in most foods especially marine foods. 2. Iodised salt. MANGANESE Present in very small amounts in animal body. Functions. 1. Activates enzyme reactions. Deficiency. 1. Animals grow slowly, bone structure affected. 2. Reproductive failure - irregular ovulation, testicular degeneration. 3. Perosis - slipped tendon and head retraction in chicks. 4. Lameness in pigs. Sources. Widely distributed in foods. SELENIUM




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Mostly known for its toxicity:- 1. Alkali disease - ingestion of plants that have a high Se content (10 - 30ppm) - dullness, stiffness, lameness, loss of hair and hoof deformities. 2. Blind staggers - ingestion of plants that have a very high Se content (4000ppm). Deficiency. 1. Exudative diathesis <-> Vit E. 2. Liver necrosis in pigs <-> Vit E. 3. Muscular dystrophy <-> Vit E. 4. White muscle disease - young animals. 5. Infertility. 6. Poor growth. 7. Embryonic death. 8. Mastitis <-> Vit E. 9. Affect the immune system - susceptibility to disease - mastitis, diarrhoea. Factors associated with Se deficiency 1. Soils - leached acid soils, high S in soil. 2. Antagonists in feed (S, Cd, Ag, As), polyunsaturated F.A. Sources. 1. Fertilizing land with Se. 2. Dosing (Selenite) and injecting - vet. 3. Mineral supplement - not advisable - toxicity. 4 H.P.C high in Se - reason for growth responses? - toxicity. 5. Chicken litter - Se content? DIGESTION OF FEED "DIGESTION" Breaking down of large insoluble compounds Mechanical, chemical, microbial "ABSORPTION" Passage of digested nutrients through the mucous membranes into the blood and lymphatic system. DIGESTIVE ENZYMES 1. Breaks down food by hydrolysis. 2. Most are present as inactive precursors (zymogen). 3. Have optimum pH 6-8 (except proteolytic enzymes - lower pH). Three main groups:- 1. Carbohydrases. amylase, maltase, sucrase, lactase.




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2. Proteolytic enzymes. pepsin, rennin, trypsin. 3. Esterases. lipase. RUMINANTS a) Digestion in mouth. Mainly mechanical - mastication - break large particles down to smaller particles. Saliva - lubricant, buffer - urea. Starch Amylase Maltose (very little) b) Digestion in rumen. Rumen contents exist in 2 phases, lower liquid phase (finer food particles) and upper one (coarser solid material), and are continually mixed by biorhythmic contractions of the walls and the coarser material arriving at the anterior end will be regurgitated, chewed and returned to the rumen. Thus food breakdown is partly physical and partly chemical (enzymes secreted by bacteria and protozoa).




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Bacteria grouped according to substances they attack: 1. Cellulose - fermenting V.F.A. 2. Starch and sugar fermenting V.F.A. and polysaccharides 3. Lactic - acid - fermenting V.F.A. 4. Vitamin synthesising B group vitamins Total number and types bacteria depend on host's diet. Normal rumen flora established as early as 6 weeks. Most of food (milk) in a newborn ruminant is diverted to the abomasum via oesophageal groove. Protozoa - 2 broad categories: 1) Those that ingest food particles and utilize simple and complex CHO (cellulose); 2) Those that generally do not ingest food particles and cannot utilise cellulose. They cannot tolerate pH < 5.5, therefore absent concentrates. 70% DM converted by M.O's is converted to soluble and gaseous compounds, absorbed into blood or lost by belching (gas). M.O's and ruminant have nearly an ideal symbiotic system, as they benefit each other. The conditions provided for the M.O's are:- 1. Anaerobic environment (Lack of 02) 2. Regular intake of food, serves as substratum for growth. 3. Constant temperature (38 C - 42 C). 4. Maintenance of pH varies in narrow range around 6,5; made possible by secretion of saliva (sheep: 6-10 /d; cattle: 50-58 /d). 5. Transportation of raw material, removal of final products and byproducts is important. Reticulum plays an important role, traps heavy objects. 6. Essential nutrients for M.O's (N, P and Co) passed back to rumen via the saliva. Rumination - up to 7-8 hrs/d on pastures or balanced roughage ration, after regurgitation the fluid is swallowed while coarse material is chewed 40 to 60 times and swallowed, large amounts saliva secreted and swallowed. Microorganisms have three important tasks: 1) Digestion cellulose by cellulase, (as no other organ or secretion can accomplish this), to V.F.A.s.




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2) Construction of A.A and ammonia, independent of external sources of A.A, and also makes use of non-protein sources (urea, chicken litter). 3) Synthesise vitamins K and water soluble vitamins. These are not the only tasks they do, also modify to a greater or lesser extent CHO's, proteins and fats, provided they stay in the rumen for long enough before they move on. c) Digestion of carbohydrates (CHO). CHO (cellulose, hemicellulose, other CHO) not attacked by digestive enzymes but by microbes, end products V.F.A.s (acetic, propionic, butyric acid). Acetic acid most predominant and roughage diets give rise to acid mixtures high in acetic acid. As the proportion of concentrates increases so the proportion of acetic acid decreases and propionic acid increases. V.F.A. absorbed directly into the blood, some end up in the small intestine where absorbed. Up to 3 kg V.F.A. produced/day by adult cow. Large amount of gas is produced - cow exceeds 30 /h. CO2 and CH4 (methane). 7% of energy produced lost as gas. Most of gas lost by eructation (belching) accumulation leads to bloat. The extent to which cellulose is digested is dependent on: 1) The degree of lignification, lignin is resistant to bacterial attack and thus hinders breakdown of cellulose; 2) The amounts of starch and sugars in the diet, an increased amount results in decreased cellulose digestion. 90% of the starch is digested in rumen, the rest is digested in the abomasum and small intestine. The great size of the rumen allows food to accumulate and sufficient time for breakdown. d) DIGESTION OF PROTEIN + NPN Protein and N-bearing bonds in the ration are digested by rumen M.O's and converted into microbial protein. Before feed mass reaches abomasum, the protein ration has undergone changes, part of it is lost as NH4 (ammonia) or the total amount of N could have even increased due to the addition of urea from saliva. 2 types protein digestion to provide A.A. :- 1) Active protein digestion (degradation) and reconstruction by means of M.O.s in reticulo-rumen. - recirculation of urea is NB. 2) Normal enzymatic hydrolysis of protein components (including microbial cells) in lower digestive tract. N-bearing bonds in the feed including urea and biuret subject to bacterial action. There is an endogenous supply from liver. Urea is recycled for the following reasons:-




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1) Additional source of N for M.O.s when N concentration is low. 2) Induces an increase in the amount of A.A. which are eventually absorbed from the lower alimentary tract. 3) Provides the M.O.s with a second chance to synthesise A.A. from NPN. Recycling of urea can change a negative N-balance into a positive balance if the ration has sufficient energy, but is deficient in nitrogen. Ruminants must not be fed more than 1/3 of total proteins in the form of NPN. If an excess is ingested disorders such as bloat, urea poisoning and acidosis can result. How do ruminants differ from monogastrics? 1. No upper incisors. 2. Their ability to ruminate (up to 8 hrs/day). 3. Ruminant is a walking fermentation vat, desirable environment for M.O.s - 3 functions: i) Make it possible to digest fibre ii) Synthesize nutrients (B complex, Vit. C and K) iii) Essential A.A. synthesised by M/O. 4. Ability to belch large volume gas produced by ruminant. 5. Stomach of the newborn. The undeveloped rumen is small and not functional and the fourth stomach (abomasum) is largest of all the stomachs. Only after ± 3 months can it be considered an actual ruminant. MONOGRASTRICS a) Digestion in the mouth Mainly mechanical, mastication is important to break up large food particles and mix it with saliva acts as a lubricant. Chemical digestion starts in mouth with the enzyme Ptyalin (Amylase). Saliva secreted by 3 pairs salivary glands: 1) Parotids (in front of each ear). 2) Submaxillary (each side of lower jaw). 3) Sublingual (underneath the tongue). b) Digestion in the stomach




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The stomach consists of a simple compartment and functions as an organ of digestion and storage. Glands of mucous membrane secrete gastric juices (water, inorganic salts, mucous, HCI acid and pepsinogen (enzyme precursor ), which initiates digestion. The acid lowers the pH to about 2,0 and also converts pepsinogen to pepsin. Pepsin splits proteins. HCI acid hydrolyses proteins and splits sucrose and prevents undesirable bacterial fermentation. Sufficiently digested, semifluid food (chyme) passes slowly through the pyloric valve into the small intestine. c) Digestion in small intestine First part is the duodenum and its function is to neutralise the acid in the chyme increasing the pH to about 8.2 - 8.4. 4 secretions enter the small intestine: 1. Duodenal juice. 2. Pancreatic juice. 3. Succus entericus. 4. Bile. Pancreatic juice consists of: 1. Trypsinogen which is converted to trypsin by a co-enzyme. Trypsin acts on proteins to produce A.A.. 2. Pancreatic lipase an enzyme that splits fats into fatty acids and glycerol. 3. Pancreatic amylase an enzyme that hydrolyses starch to disaccharides. 4. Bile a secretion from liver that activates lipase and amylase, helps to emulsify fats so that they are exposed to enzymes, maintains pH (7-8). Bile salts form water soluble complexes with fatty acids, enabling them to be easily absorbed by blood. Carbohydrates and fats are virtually exclusively digested and absorbed in small intestine. CHO's broken down into simple monosaccharides which are absorbed into the portal circulation. Proteins are digested and broken down, into A.A. which are absorbed by the small intestine. The small intestine is the main site of absorption of nutrients. d) Digestion in large intestine Glands in the large intestine are mainly mucous glands and therefore digestion is brought about by enzymes carried down in the food and by microbial activity. There is extensive microbial activity in the large intestine, especially the caecum, bacteria is mainly of a proteolytic type attacking undigested proteins. A certain amount of material is resistant to digestion by enzymes secreted by the alimentary canal (cellulose, many hemicelluloses and lignin) are broken down to limited extent in the pig, but this is small compared to the horse and ruminant. The horse has a system (large caecum and colon) that deals with fibrous foods. These polysaccharides are broken down into volatile fatty acids (acetic, propionic and butyric acid). Bacterial action may




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synthesize some of the B vitamins, which are absorbed, but the amount is insufficient and dietary source is therefore needed. POULTRY NUTRITION Digestion and absorption are determined by: 1) Rate of passage of ingesta 2) Sequential exposure of ingesta to digestive enzymes. The beak will break up food particles to a limited extent. Most food whole and swallowed by propelling the food down the gullet. Poor sense of taste compared to humans but the chicken will still choose what it wants to eat. Salivary glands, present in the mouth and pharynx, moistens food before it moves into the oesophagus. Oesophagus 25 cm in length and it has a cranial and caudal part. Cranial part of the oesophagus has mucous glands which makes the food more liquid. Where it enters the thoracic cavity it has a crop which is a glandless storage organ. Rapid contractions get the food to the crop as quickly as possible. The food then moves from the crop to the caudal part by slow peristaltic movements depending on the state of the proventriculus and gizzard. The crop contracts every 1 - 1.5 minutes when empty, if full contractions may cease completely. Proventriculus Contains gastric glands which produce HCI and enzymes (pepsinogen) which are mixed with the food. Rate of passage of food dependent on the crop, the caudal oesophagus and the amount of food in the gizzard. Gizzard Well developed muscular chamber 5 cm in diameter, 2.5 cm thick has a tough, thick inner lining. Main function is to grind food, the power comes from the muscles to break down the food particles. The efficiency of this grinding is increased if grit is present (Dolomitic Grit), only needed if grains etc. are fed. Site for peptic (pepsinogen) hydrolysis. The thinner muscles are used to move the food to the duodenum, these movements depend on how full or empty it is and the nature of the food. Hard grains decrease the rate of contractions become short and sharp, softer food results in contractions of longer duration. Contractions of 3 times a minute when full, may cease when empty. Small intestine Consists of: a) Duodenum. b) Jejunum. c) Ileum.




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About the same diameter throughout, difficult to distinguish where the sections begin and end. Opening from the gizzard the pyloric chamber has ridges which act as a filter to prevent large particles including grit to pass through. A thick layer mucous acts as a barrier against highly acid material entering the duodenum. Duodenal glands are the source of secretions, mainly amylase also Proteases and Sucrases. Bile and pancreatic ducts are toward the end of the duodenum, this denotes the start of the Jejunum. Pancreatic juice contains enzyme precursors. Bile - produced by the liver (1 ml/hour) is stored in the gall bladder. Very little structural difference between jejunum and ileum - major absorptive area of the intestine. Caeca Paired blind ending sacs with a thin neck region ending in large bulbous sacs. Function in bacterial fermentation of food residues. Undigested food is first ingested into the colon and by reverse peristalsis moves up into the caeca or straight into the cloaca. Villi at the opening of the caeca prevent any solid material moving into the caeca. Contents of the caeca is chocolate in colour. Small amounts of fibrous material (cellulose) find their way into the caeca where it is broken down by micro organisms as there is no cellulase secreted by the animal. The fermentation yields volatile fatty acids, certain vitamins and amino acids which are not absorbed, but the bird eats its droppings (COPROPHAGY). Cloaca Water and electrolytes are absorbed in this area, facilitated by oscillations of the digesta and fluid. Feed intake theory The amount of food consumed is governed by the concentration of the first-limiting nutrient (amino acid, energy, vitamin, trace element). The consequence of this overconsumption to satisfy the first-limiting nutrient is excess fat deposition. Actual food intake depends on: 1. Genotype. 2. Current state (maturity, state of fat stores). 3. Feed consumption (balance between E and the first-limiting nutrient, feed bulk, toxins) 4. Environmental hotness (excess heat). Birds seek to eat an amount of food such that they have enough nutrients to just achieve their potential lean growth. Birds have no wish to become fat, i.e. to gain more fat than their minimum requirement. Fat growth above minimum is a sign of nutrient under-supply. They stop eating before they have achieved their potential lean growth, if eating more would make them too hot, cause a build-up of some toxins or reach a bulk constraint. They will form fat as a way of getting closer to an adequate nutrient intake, but not to produce heat if they are cold. Summary of feed intake theory. Concentration of first-limiting nutrient (A.A., energy, vitamin, trace element).




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Overconsumption excess fat deposition. Actual food intake depends on: Genotype, current state, feed consumption and environmental temperature. Eat to achieve potential lean growth, have no wish to become fat. Cold conditions - food has lower nutrient : energy ratio. Hot conditions - E level too high, push up nutrient concentration, drop E level or drop temperature of room. Energy Dietary E used for: (1) Supply E for work. (2) Converted to heat. (3) Stored as body tissue. Partitioning of dietary E. Sources of E - fats or lipids. Advantages: (1) Concentrated source of E. (2) Solvent, aids in absorption of fat soluble vitamins. (3) dustiness. (4) Making pellets easier. (5) palatability. (6) Helps alleviate heat stress. Reasons broilers use E from oil: (1) Lower HI when oils used. (2) Higher E density in feed. (3) Synergism between sources. Amino acids. A.A. may be in a feed but not available, can't ensure correct levels. Heat treatment of proteins bind A.A. and they become unavailable. Requirement varies during stages of growth, cannot use one A.A. profile for complete period. A.A. differ depending on balance of other A.A. being fed. Factors to be considered when choosing an A.A. allowance for laying hens: 1. Factors concerned with feed. 2. Factors concerned with bird. 3. Factors concerned environment.




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If fed according to mean of flock, half of birds underfed. Consequences are lower egg output increased food intake and decreased FCE If broilers are being fed need to ask some questions: 1. What level should be fed? 2. When should feed be changed? 3. What basis should changes be made? Undersupply nutrients cause: 1. FI to increase. 2. Body mass gain decreases. 3. Fat content will increase. Oversupply causes: 1. Body mass gain to be maximised. 2. FI reduced. 3. Fat content is minimal. 4. Cost of production slightly increased. Factors affecting apparent protein quality: 1. Factors inherent in the animal. a) Age b) Strain c) Growth rate. 2. Nutritional factors. a) Protein level b) E level Adverse effects of feeding feeds containing disproportionate amounts of A.A. a) Toxicities. b) Antagonists. c) Imbalances. Feed imbalances cause bird to eat less resulting in depressed growth rate. If one can increase FI can increase growth rate. Ways to do this: 1. Drop temp. 2. Decrease energy content of feed. 3. Inject insulin.

MANAGEMENT STRATEGIES DURING DROUGHT




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THE 4 PRIMARY RULES OF DE-STOCKING 1. DECIDE EARLY. The sooner a problem is identified, the sooner appropriate action can be taken.

The practice of keeping young cows (less than 4 years old) at the expense of more productive middle-aged cows (4-7 years old) when culling is finally started.

2. SELL EARLY. The sooner de-stocking adjustments are made, the less severe herd reductions will

need to be. 3. THINK ABOUT IT. Maximise available options and minimise long-term negative impacts on the

forage resource (your grazing areas) 4. AVOID A DUST BOWL. Have enough residual grass cover to capture and utilise any limited rainfall

and reduce evaporative losses. COMMON DE-STOCKING MISTAKES

There are three common mistakes farmers make when faced with forced liquidation of the breeding

herd:

1. Do nothing now in the hope that rain will come eventually or that you will find additional grazing later in the year (just when everybody else is also looking).

2. When the decision to reduce stock is made, the most common (and mistaken) strategy is

to early wean calves and then hope conditions improve and that the cows will not have to be sold.

3. The practice of keeping young cows <4yrs at the expense of more productive older cows 4

– 7 yrs old. Culling calves at this time will not decrease the total forage demands of the herd. Calves only consume 15-20% of consumed by their dams. Light weight, early-weaned calves have little value in current market conditions. Use early weaning as a management tool to improve cow condition before calving - not to decrease forage demand. A commercial ranch cannot afford to purchase hay to survive a drought or an overstocked situation. Short-term management practices such as feeding hay are expensive and seldom the best alternative. Decreasing forage demand is imperative during drought and requires the sale of breeding stock. Producers should not cull cattle and use the money to buy feed or hay for the remaining cows. To do so will cause a ranch to come out of a drought without any cows or any money left!




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STRATEGY TO BE ADOPTED.

1. Cull any cow, which does not currently have a calf at her side. Be ruthless - this is not the time to wait for next year’s income.

2. Cull any replacement heifers, which are not already in production. During drought, first

calvers will wean the lightest calves and have the lowest re-breeding potential in the entire cow herd.

3. Look at your cowherd objectively when they come in for dipping. Check teeth, feet, legs,

udders and the quality of the calf at their side. Consult your herd records during this process and do not overlook cows with a marginal production record. This is the ideal time to get rid of any dodgy ones.

4. Checking teeth is especially important. Cows with poor teeth will be the first group to

decline in a drought environment as the grazing gets tougher.

5. Once all the marginal cows have been removed, the only culling option left is based on uniformity. Sell the smaller and the larger end of cows - get rid of the extremes.

Of course it is very difficult to cull a cow with a calf but remember the goal is to remove a sufficient number of cows to ensure that adequate forage is available to carry those cattle that remain. De-stocking decisions are never easy to make and are seldom made without substantial cost. Remember early de-stocking adjustments will be less severe than later ones and will lead to great market flexibility and net realisation. The strategies outlined here are designed to cull cows of the least immediate economic benefit and to maximise individual animal production in the remaining herd.




Documents

Animal nutrition (Compiled by Austine Mabika)