(a) Write composition of egg yolk citrate dilutor and method of its preparation. (10 marks) (b) Explain the process of…

(a) Egg Yolk Citrate Dilutor Egg yolk citrate (EYC) is the standard extender for liquid bovine semen. It has two components: 2.9% sodium citrate dihydrate solution as buffer, and 20% (v/v) fresh egg yolk, the protective agent whose lipoproteins and phospholipids guard the sperm membrane against cold shock.

Preparation: dissolve 2.9 g sodium citrate dihydrate in 100 mL double-distilled water and sterilise by autoclaving. Wash a fresh hen's egg, disinfect the shell with alcohol and separate the yolk from the white aseptically; rolling the yolk on sterile filter paper removes albumen. Puncture the yolk membrane and add 20 mL yolk to 80 mL cooled citrate solution, mixing gently without foaming. Add penicillin (1,000 IU/mL) and streptomycin (1 mg/mL). Let it settle and use the extender at about 5°C. For frozen semen, glycerol (about 7%) is added as cryoprotectant in the second fraction.

(b) Erythropoiesis Erythropoiesis is the formation of red blood cells. Its site shifts with age: yolk sac in the early embryo, then liver and spleen in the foetus, and red bone marrow after birth.

Pluripotent haemopoietic stem cells give rise to myeloid progenitors, then BFU-E and CFU-E. Hypoxia makes the kidney (peritubular interstitial cells) release erythropoietin (EPO), which drives CFU-E through proerythroblast, basophilic, polychromatic and orthochromatic erythroblast stages. Haemoglobin synthesis starts early and the cell shrinks as haemoglobin accumulates. The orthochromatic erythroblast extrudes its nucleus to form a reticulocyte, which is released into blood and matures into an erythrocyte within one to two days.

Iron, copper, vitamin B12, folic acid, B6 and protein are essential. Rising oxygen delivery suppresses EPO, a negative feedback. Small-erythrocyte species such as goat and sheep have high RBC counts.

(c) Adaptation to Extreme Climates Animals keep core temperature within narrow limits by combining physiological, morphological, behavioural and metabolic adjustments.

In heat: peripheral vasodilation, sweating (cattle, horse) or panting (dog, sheep), higher respiratory rate, and reduced feed intake and thyroid activity to cut metabolic heat. Morphological features include loose skin, large dewlap, short sleek coats and light coat colour; Tharparkar and Sahiwal cattle and Chokla sheep tolerate arid heat well. Behaviour includes shade-seeking, wallowing (buffalo) and night grazing. Camels tolerate dehydration by letting body temperature fluctuate and by concentrating urine.

In cold: shivering and non-shivering thermogenesis (brown fat in neonates), peripheral vasoconstriction, countercurrent heat exchange in limbs, thick coat and subcutaneous fat, huddling, and higher feed intake. Hibernation and migration are further strategies in some species.

(d) Partitioning of Food Energy Gross energy (GE) is the heat released on complete combustion of the feed. Subtracting faecal energy gives digestible energy (DE). Subtracting urinary energy and gaseous energy (mainly methane in ruminants) from DE gives metabolisable energy (ME).

ME divides into heat increment (HI), the heat produced in digestion, fermentation and nutrient metabolism, and net energy (NE). NE has two parts: NE for maintenance (basal metabolism, voluntary activity and temperature regulation), which yields no product, and NE for production (growth, fattening, milk, pregnancy, work, wool, eggs).

Efficiency of use of ME is higher for maintenance and lactation (about 60–70%) than for growth and fattening (about 40–50%), and lower on fibrous diets. Total digestible nutrients (TDN) and starch equivalent are practical expressions. Rations are formulated on this basis to reduce wasteful losses.

(e) Feeding of Calves, Birth to Three Months Colostrum: feed the first colostrum within one to two hours of birth, and about one-tenth of body weight daily for the first three days, in two or three feeds. It supplies immunoglobulins, vitamin A and laxative action; poor intake causes failure of passive transfer.

Milk: from the fourth day, whole milk or milk replacer at about one-tenth of body weight daily up to one month, then about one-fifteenth till weaning. Buckets and nipples must be kept clean.

Solid feed: offer calf starter (about 20% crude protein, highly digestible), clean water and good-quality hay from the second week to stimulate rumen development; papillae grow with volatile fatty acids from starter fermentation.

Weaning: milk is reduced gradually and stopped at 8–12 weeks, when starter intake reaches about 1 kg/day for the calf. Add deworming, vaccination, dehorning and hygiene.