(a) Describe causes of different types of anoestrus in dairy cows and suggest their remedial measures. (15 marks) (b) Describe…

(a) Anoestrus in Dairy Cows: Causes and Remedies Anoestrus is absence of observed oestrus. Types: (i) true anoestrus, with inactive ovaries (hypofunction or atrophy), or ovaries held static by a persistent corpus luteum, luteal cyst, pyometra, mummified foetus or pregnancy; (ii) subestrus or silent heat, with normal cyclicity but weak or undetected signs; (iii) postpartum anoestrus, the commonest in Indian dairy cows and buffaloes, where cyclicity does not resume within 60–90 days of calving.

Causes: negative energy balance and protein, phosphorus, copper, cobalt and selenium deficiency suppress GnRH and LH pulses; high milk yield; heavy suckling; uterine infection and retained placenta; heat stress; poor heat detection (for subestrus); and parasitism or chronic disease.

Remedies, matched to cause:

• Correct feed: balanced ration, area-specific mineral mixture, bypass fat, deworming.
• Inactive ovaries: GnRH or hCG, eCG (PMSG), and progesterone devices (CIDR or PRID) followed by PGF2α.
• Persistent CL or luteal cyst: PGF2α or analogue, and treat pyometra.
• Follicular cysts: GnRH or hCG.
• Fixed-time AI by Ovsynch (GnRH, PGF2α after seven days, second GnRH about 56 hours later, AI at 16–18 hours) removes the need for heat detection.
• Management: record keeping, tail-paint or activity monitors, treat uterine infection early.

(b) Respiration in Poultry The avian lung is small, compact and non-expansile, fixed to the ribs and vertebrae, and has no diaphragm. Air flows through the primary bronchus into secondary bronchi and then into parabronchi, where gas exchange occurs across blood capillaries. Nine air sacs (cervical, clavicular, two cranial thoracic, two caudal thoracic, two abdominal) act as bellows but are not sites of gas exchange. Movement of the sternum and ribs by muscles changes the volume of the body cavity.

Mechanism: one breath needs two cycles. First inspiration: fresh air passes through the lungs into the caudal air sacs, and some enters the lungs. First expiration: air from the caudal sacs passes into the lungs. Second inspiration: air from the lungs moves to the cranial sacs. Second expiration: it is expelled through the trachea.

Because flow through the parabronchi is almost unidirectional and cross-current to blood flow, gas exchange is more efficient than in the mammalian tidal system. Expiration is also active. Panting through air sacs aids cooling.

(c) Protein Requirement of Growing Calves Use the factorial method: requirement equals the protein needed for maintenance plus protein deposited in gain, corrected for efficiency of use.

Step 1: maintenance protein covers scurf (skin and hair), endogenous urinary and metabolic faecal losses, all rising with body weight or feed intake.

Step 2: protein for gain equals daily gain multiplied by protein content of gain (about 17–20% in young calves), divided by the efficiency of use of absorbed protein, around 0.5.

Step 3: add both to get metabolisable protein, then convert to crude protein using the diet's digestibility and rumen microbial supply.

Illustration (assumed values): a 100 kg calf gaining 500 g/day deposits 0.5 × 18% = 90 g protein. At 0.5 efficiency, growth needs about 180 g metabolisable protein, to which maintenance (assume 40 g) is added to give about 220 g.

In India, ICAR feeding standards give DCP and TDN per animal by weight and gain. Preruminant calves need milk or milk replacer with high-quality protein, whereas weaned calves also use microbial protein and bypass protein from soybean meal or groundnut cake.

(d) Calorie:Protein Ratio in Poultry The calorie:protein ratio is the metabolisable energy (kcal/kg) divided by crude protein (%), commonly expressed as ME:CP. Birds eat to satisfy energy requirement, so an ideal ratio ensures adequate protein and amino-acid intake at that energy intake.

Typical values: broiler starter about 3,000 kcal ME and 22–23% CP (ratio about 130); finisher about 3,100–3,200 kcal and 19–20% (about 160); layers about 2,600–2,700 kcal and 16–17% (about 160).

A wide ratio (excess energy) causes fat deposition, fatty liver and poor egg and meat yield. A narrow ratio (excess protein) wastes expensive protein as uric acid, raises litter ammonia and heat increment, and costs more. In heat stress, intake falls, so nutrient density and the ratio must be adjusted. Because feed is 60–70% of production cost, balancing cheap sources such as maize and soybean meal helps economics.