(a) Write short notes on the following : (i) Metabolizable energy (ii) Role of pancreas and liver in digestion (iii) Transgenesis…

(a) Short notes

(i) Metabolizable energy

Metabolizable energy (ME) is the feed energy available to the animal after faecal, urinary and gaseous (methane) losses: ME = GE − FE − UE − gaseous energy. It is expressed in MJ or Mcal/kg DM, and methane loss is about 6–10% of GE in ruminants. ME divides into heat increment and net energy, and it is the practical unit for ration formulation; maize grain supplies about 13.5 MJ ME/kg DM.

(ii) Role of pancreas and liver in digestion

The pancreas secretes trypsinogen, chymotrypsinogen, procarboxypeptidase, α-amylase and lipase, with bicarbonate that neutralises acid chyme; enterokinase converts trypsinogen to trypsin, which activates the other zymogens. The liver secretes bile salts, which emulsify fat and form micelles for absorption of fatty acids and fat-soluble vitamins; without bile, fat digestion fails and steatorrhoea follows. The liver also stores glycogen, makes plasma proteins and detoxifies ammonia.

(iii) Transgenesis

Transgenesis is the stable insertion of foreign DNA into the germline so that it passes to offspring. Methods are pronuclear microinjection, nuclear transfer with transfected cells, lentiviral vectors and CRISPR-Cas9. Examples are sheep secreting human α1-antitrypsin in milk and cattle producing human lactoferrin. Uses are pharming, disease models and production traits, under biosafety regulation.

(iv) Prebiotics as feed additives

Prebiotics are non-digestible ingredients that selectively stimulate beneficial gut bacteria, unlike probiotics, which are live organisms. Examples are inulin, fructo-oligosaccharides, galacto-oligosaccharides and mannan-oligosaccharides, used at about 0.2–0.5% of the diet. Fermented to short-chain fatty acids, they lower gut pH, suppress pathogens and improve feed conversion in calves, piglets and poultry.

(b) Crossbred cattle breeds developed in India and types of crossbreeding

Crossbreeding is mating animals of two different breeds to combine the milk yield of Bos taurus with the hardiness of Bos indicus, using heterosis.

Indian crossbreds: Karan Fries (Holstein-Friesian × Tharparkar, NDRI), Karan Swiss (Brown Swiss × Sahiwal, NDRI), Frieswal (5/8 Holstein-Friesian × 3/8 Sahiwal, with Military Farms), Sunandini (local × Brown Swiss, Jersey and HF, Kerala), Vrindavani (Hariana × HF, Jersey and Brown Swiss, IVRI) and Phule Triveni (Gir × HF × Jersey, Maharashtra).

Types of crossbreeding:

1. Two-breed cross: a local female with an exotic bull; the F1 is used for milk.
2. Grading up: bulls of one improver breed used on successive generations, so the herd approaches the improver breed.
3. Criss-crossing: exotic and indigenous bulls used in alternate generations, retaining about 67% heterosis.
4. Three-breed rotation: a third breed is added in the rotation.
5. Synthetic or composite breed: crosses are mated among themselves and selected, as in Frieswal, Sunandini and Vrindavani.
6. Terminal cross: crossbred dams mated to a third-breed sire, and all progeny sold.

The aim in India is a stable level of about 50–62.5% exotic blood.

(c) Herd recording and its significance for efficient dairy farm management

Herd recording is the systematic identification of every animal and regular collection of its production, reproduction, health and pedigree data.

Records kept: identification and pedigree; milk yield, fat and SNF; heat, service, pregnancy, calving and calving interval; vaccination and treatment; feed and body condition score; costs and culling.

Significance:

• Genetic improvement: records with pedigree allow selection of high-yielding dams and progeny-tested bulls.
• Health: a sudden fall in yield or rise in somatic cell count flags mastitis or metabolic disease early.
• Reproduction: long calving intervals and repeat breeders are detected and dry-off dates planned.
• Feeding: lactation and body-condition data allow grouping and ration changes that cut feed cost per litre.
• Economics: culling of poor producers, profit calculation and records for credit.

Computerised systems such as NDDB's INAPH store these data and produce action lists.