Chapter 4

1. Chapter 4 The Feeding requirements of Farm Animals

2. Energy • Energy available in digestible food • Energy that can be utilized in body cells is based on mediating compounds that make oxidation possible at low temp. • Important mediating compound: adenosine triphosphate (ATP)  has three energy rich phosphate bonds • In interaction with ADP and AMP the ATP can store or release energy (as with a battery) • Basic reaction: Food + O2 + ADP + P  CO2 + H2O + ATP

3. Gross energy • The quantity of chemical energy present in food is measured by converting it into heat energy, and determining the heat produced • This conversion is carried out by the complete oxidation of the food by burning it in a bomb calorimeter • Not much variation in GE between feedstuffs, thus not much value when comparing different feedstuffs • Fails to take into account the losses of energy occurring during digestion and metabolism

4. Digestible energy • It is the gross energy intake (BE) less the energy contained in the faeces • There is a great resemblance between the DE and the total digestible nutrients (TDN) TDN = digestible CP + digestible CF + digestible NFE + digestible fat  2.25

5. Metabolisable energy • The ME of feed is the DE less the energy lost in urine and combustible gases (methane) • In non-ruminants energy losses as fermentation gases are negligible but in ruminants it can be as much as 6 to 10% of total energy (BE) of the food • For foods such as concentrates which are digested to much the same extent by ruminants and non-ruminants, ME-values will be greater for non-ruminants

6. Heat increment of foods • It is the increase in heat production because of feed intake • ME is not used for body function with 100% efficiency, a part of it is lost as heat For example, if glucose is oxidised in the formation of ATP, the efficiency of free energy capture is only 44%, 56% being lost as heat • Energy loss through heat, fermentation by MO, energy for mastication • Energy loss directly as heat through evaporation

7. Net energy • Net energy is the difference between ME and the heat increment (HI) • The NE of a food is that energy which is available to the animal for body maintenance and for the different forms of production • A certain feed’s NE-value vary according to the type of animal and the physiological function the energy is used for, NEm = NE for body maintenance NEf = NE for fattening NEg = NE for growth NElakt = NE for milk production

8. Energy Brute energy Digestible energy Energy in faeces Metabolisable energy Energy in methane and urine Nett energy Conversion losses (heat loss)

9. Protein • The fat free, moisture free body of the animal consists of 80% protein and 20% minerals • Moisture free full milk has 30% protein • Wool fibers consist of pure protein Without protein the animal cannot grow or produce

10. Amino acids as building blocks for proteins • Building blocks for synthesis of cells • Building blocks for synthesis of enzymes and hormones • Detoxicating harmful substances • Energy can also be produced from amino acids

11. Protein synthesis • All enzymes are proteins • The building blocks of proteins are amino acids • Characteristics of proteins depend on the sequence of amino acids in the protein • This sequence depends on the message from the genes • DNA produces RNA and RNA carries the instructions to the ribosomes where the work is done • Amino acids in the cytoplasm that are used as building blocks come from digested food

12. Protein synthesis • mRNA is built in the nucleus by DNA & carries the code to ribosomes in cytoplasm • The code is sent by codons (three consecutive bases) • Codon specifies particular amino acid • tRNA identifies amino acid by means of anticodon corresponding to codon of mRNA • tRNA carries amino acid to ribosome, where proteins are built along the mRNA molecule • The kind of protein built depends upon kind, number and arrangement of amino acids

13. Amino acids (a/a) • Especially important practical implications in the feeding of non ruminants • Divided into essential and non-essential a/a • Both are equally important to the animal • Essential refers to feed – essential a/a need to be included in the feed, non essential a/a can be synthesized in the tissue.

14. Essential amino acids • Especially important practical implications in the feeding of non ruminants • The 10 essential a/a have to be provided by the diet because: • It can not be synthesized in the body tissues • It is synthesized so slowly that normal production cannot be sustained • Amino acids that are available are de-aminated to form an amino acid that is not readily available • N-part of amino acid that is “wasted”, is excreted in the urine

15. Protein quality for ruminants • The amount and quality of true protein that reaches the lower digestive tract and that can be absorbed there • It is influenced by: • Rumen degradability of the protein • DOM ingested for rumen microbe protein production • Efficiency of conversion of RDP to microbial protein (100% for a/a-N and 80% for ureum-N) • Digestibility and absorption of amino acids from microbial protein or diet protein

16. Protein quality for monogastric animals • Biological Value • EAAI (Essential Amino Acid Index) • Ideal protein • These measure have no impact on ruminants, for amino acids get changed in the rumen by the micro organisms.

17. Biological value • BV = N intake – (manure N – MMN) – (urine N – EUN) x 100 / N intake – (manure N – MMN) • * Nitrogen intake • * Nitrogen excretion in manure • * Nitrogen excretion in urine • * Metabolic manure nitrogen (MMN) • * Endogenic urine nitrogen (EUN)

18. EAAI (Essential Amino Acid Index) • Essential a/a ratio compared to the amino acid ratio of an egg • Arbitrary BV value of 100 is given to the egg and feedstuff is then compared with that.

19. Ideal protein • The lean muscle of a pig is analysed and the a/a composition determined. • Is used as example of “ideal” a/a composition in a ration.

20. Practical use of NPN sources NH2 Urea Nitrogen content of 46% Equivalent to a CP content of: 46.4 × 6.25 = 290% CP C = O NH2 Urea is hydrolysed by the urease activity of the rumen micro-organisms with the production of ammonia: NH2 NH2 C = O + H2O  2NH3 + CO2

21. Practical use of NPN sources Factors affecting the utilization of NPN: • Source of readily available energy so that microbial protein synthesis is enhanced and wastage reduced (the entry of readily available carbohydrate into the rumen will bring about a rapid fall in rumen pH and so reduce the likelihood of toxicity – at a lower pH the urease activity is lower) • Slower intake of NPN over longer period, more efficient utilization and lower toxicity • Availability of natural protein in diet • A ration with enough protein will make the inclusion of NPN needless

22. NPN toxicity • Sheep can die with an intake of 8.5g/day of urea ..... others live after intake of 100g/day • Ammonia is the toxic agent • Ammonia is most toxic at high ruminal pH owing to the increased permeability of the rumen wall to ammonia (that is why enough readily available carbohydrate is necessary with NPN) • An adaptation period when feeding NPN is important

23. Symptoms of urea toxicosis • Muscular twitching • Excessive salivation • Tetany • Bloating • Respiration defects (rapid shallow, slow deep) • Ataxia Treatment: Dose with large volumes of diluted vinegar

24. Feeding of urea Urea with molasses • Diluted solution of urea and molasses sprayed on dry grassland, hay or straw. • Solution of 1kg urea per 10kg undiluted molasses as a supplement on low protein veld grazing or low grade roughage.

25. Feeding of urea Mineral licks and lick blocks as carriers • Many mineral licks and lick blocks include urea. • Salt is often used as a regulator of urea. • Hardness of lick blocks also influences the intake.

26. Feeding of urea Urea in concentrated rations • Urea is commonly included in concentrated rations • Not more than one-third of the dietary nitrogen should be provided as urea • Limit the inclusion to 1% because: • Danger of toxicity • Urea is bitter and lowers intake of feed • Make sure that urea is mixed properly with the concentrate

27. Minerals for farm animals The term ‘essential mineral element’ is restricted to a mineral element which has been proved to have a metabolic role in the body. Before an element can be classed as essential it is generally considered necessary to prove that diets lacking the element cause deficiency symptoms in animals.

28. Calcium • Most abundant mineral element in the animal body (40% of body ash) Functions: • Transmission of nerve impulses • Normal contractile properties of muscle • Concerned in the coagulation of blood • Important part of milk

29. Calcium • The skeleton is not a stable unit in the chemical sense, large amounts of the Ca and P in bone can be liberated by resorption. • This takes place particularly during lactation. • This resorption of Ca is controlled by the action of the parathyroid gland, which is stimulated if animals are fed on a low Ca diet. • The skeleton is an important reservoir for Ca and makes an important contribution to production.

30. Calcium(deficiency symptoms) • Young growing animals: • Adequate bone formation cannot occur  rickets  misshapen bones, enlargement of the joints • In adult animals: • Osteomalacia  Ca in bone is withdrawn and not replaced  bones become weak and are easily broken • Milk fever (parturient paresis)  commonly occurs in dairy cattle shortly after calving • Sources of Ca: • Green leafy crops, especially legumes, animal by-products, dicalcium phosphate

31. Phosphorus • Closely associated with Ca in the body Functions: • Bone and teeth formation • Involved in energy metabolism • Part of DNA and RNA

32. Phosphorus(deficiency symptoms) • Rickets • Osteomalaci • Pica (depraved appetite) • P-deficient Northwestern Cape • Infected with Clostridium botulinum • Poor growth and reproductive performance • Sources: Phosphates, steamed bone meal, cereal grains, oil seed meal

33. Potassium Functions: • The essential function of cell osmosis and maintenance of electrolyte balance • Enzyme activator • Muscle/verve function Deficiency symptoms: • Decrease in feed intake, loss of hair glossiness Food sources: • Legume forages, potassium chloride, potassium sulphate

34. Sodium and chlorine Functions: • Acid-base balance • Maintenance of the normal tension in muscles, nerves and arteries Deficiency symptoms: • Reduced appetite, incoordination weakness, shivering Sources: • Common salt Ruminants have the ability to work very economically with NaCl and can get rid of large quantities through the urine

35. Magnesium • In large quantities in the skeleton, as Ca & P • Young animals able to mobilize 1/3 of Mg in skeleton, while adult animals will show a deficiency sooner Functions: • Activate enzyme systems, especially those that are important for transmission of nerve impulses and muscle contraction • Electrolytic role in buffer systems (except K the most abundant cation in blood)

36. Magnesium Deficiency symptoms: • Young animals  low serum-Mg, tetany-increased excitability • Adult ruminants  hypomagnesaemia, magnesium tetany, grass staggers (nervousness, tremors, twitching of the facial muscles, staggering gait, convulsions) Sources: • Wheat bran, dried yeast and most vegetable protein concentrates, especially cottonseed cake and linseed cake, Mg-oxide

37. Sulphur • Most of the S in the body occurs in proteins containing the amino acids cystine, cysteine and methionine • The vitamins, biotin, and the hormone, insulin, also contain sulphur • Deficiency is not usually considered, since the intake is mainly in the form of protein and a deficiency of S would indicate a protein deficiency. In ruminant diets in which NPN is used as a partial nitrogen replacement for protein N, S may be limiting for synthesis of cysteine, cystine and methionine

38. Iron • Form structural part of haemoglobin, that is responsible for the oxygen transportation ability of blood • Activate different enzyme systems Deficiency symptoms: • Nutritional anemia, pale mucus membranes, panting Sources: • Leafy green forages, hays, grains

39. Copper Functions: • Vital role in activating enzyme systems • Important role in the process of blood formation (necessary for haemoglobin formation) • Maintenance of central nervous system • Necessary for the normal pigmentation of wool and hair • Plays an important role in ‘crimp’ in wool • Role in enzyme systems that are responsible for calcification of the skeleton

40. Copper Deficiency symptoms: • Anaemia, even when enough Fe is available • Degeneration of the brain stem and spinal cord (sway-back) • Depigmentation of hair and wool • Wool lacks crimp and is referred to as ‘stringy’ or ‘steely’ wool • Bone abnormalities

41. Copper Sources: • Cu in pastures influenced by the pH of the soil and the type of pasture. On high pH the availability of the Cu is lower • Cu is stored in the liver • Cu is widely distributed in foods and under normal conditions the diet of farm animals is likely to contain adequate amounts • Seeds and seed by-products are usually rich in copper, but straws contain little

42. Copper toxicity • Continuous ingestion of copper in excess of nutritional requirements leads to an accumulation of the element in the liver • This accumulation leads to copper toxicosis • Sheep are very susceptible for Cu-toxicosis • It is unwise to administer copper supplements to sheep unless symptoms of deficiency occur

43. Manganese • The highest concentration in the body occurring in the liver and bones • The amount of Mn in the animal body is extremely small Functions: • Important as an enzyme activator • This enzymes are all important in carbohydrate-, fat- and protein metabolism and the calcification of bone

44. Manganese Deficiency symptoms: • Cattle and sheep  delayed oestrus and depressed reproduction, birth of calves with weak twisted legs and enlarged joints, dull coat, brown edge of black spot on Friesians Sources: • As with Cu and Fe, low accessibility at high pH of the soil • Most green foods contain adequate amounts • Commercial mineral supplements

45. Cobalt • Required by micro-organisms in rumen for the synthesis of vitamin B12 • Vitamin B12 (4.5% Co) is necessary for the synthesis of haemoglobin and for normal growth and production of animals Deficiency symptoms: • Wasting disease, pining Sources: • Cobalt-containing salt licks or dosing with cobalt sulphate

46. Iodine • Concentration in animal body very small • Constituent of the hormone, thyroxine, produced by the thyroid gland • Hormone controlls the metabolic rate Deficiency symptoms: • Enlargement of thyroid gland (endemic goitre) • Breeding animals give birth to hairless, weak or dead young • Adult animals  early aging Sources: • Foods of marine origin, iodised salt

47. Zinc • High concentrations in the skin, hair and wool of animals • Important for acid-base balance in body • Important role in natural immunity of animals (mastitis) • Ca work antagonistic against Zn Deficiency symptoms: • Parakeratosis (scabs) in pigs Sources: • Bran and germ of cereal grains • Yeast is a rich source

48. Selenium • In South Africa it is not a problem (deficiency is actually better than excess because of toxicity) • An acute deficiency leads to muscular dystrophy in lambs and calves (white muscle disease) • Functional interaction between selenium and vitamin E

49. Fluorine • Concentrated in the bones and teeth • Important as a trace element in preventing dental caries • The element is very toxic, and a level in the diet above 20 mg/kg causes fluorosis in which the teeth become pitted and worn and sensitive • Fluorine is a cumulative poison, and the ingestion of small amounts over long periods of time may produce toxic symptoms

50. Vitamin requirements • Very important for animals, but in very small amounts compared with other nutrients • Two main groups: • Fat-soluble vitamins • Water-soluble vitamins