(a) Describe the factors regulating glomerular filtration rate in animals. (15 marks) (b) Enlist the objectives and describe the…

(a) Factors regulating glomerular filtration rate

GFR is the volume of plasma ultrafiltrate formed by all glomeruli per unit time (dog about 3–5 ml/min/kg, cattle 1–2 ml/min/kg). GFR = Kf × NFP, where Kf is the ultrafiltration coefficient (permeability × surface area) and net filtration pressure NFP = PGC − (PBS + πGC), about 55 − 15 − 28 ≈ 12 mmHg in the dog.

Determinants: afferent dilatation or efferent constriction raises PGC and GFR; the reverse lowers it. Raised Bowman's-space pressure (ureteral obstruction) or plasma oncotic pressure lowers GFR, and mesangial contraction lowers Kf.

Regulation: GFR stays nearly constant over mean arterial pressure of about 80–180 mmHg.

1. Myogenic autoregulation: stretch of the afferent arteriole makes it constrict and restores PGC.
2. Tubuloglomerular feedback: more NaCl at the macula densa releases adenosine/ATP, which constricts the afferent arteriole; low NaCl releases PGE₂ and NO and renin, dilating it.
3. Renin–angiotensin: angiotensin II constricts the efferent arteriole more than the afferent, so GFR is preserved when flow falls.
4. Sympathetic nerves: intense stimulation constricts the afferent arteriole (α1) and lowers GFR.
5. Hormones: ANP dilates the afferent arteriole; prostaglandins protect flow in hypovolaemia.

Stable GFR gives the tubules a constant load for precise reabsorption.

(b) National Programme for Dairy Development: objectives and components

NPDD is a Central Sector scheme of the Department of Animal Husbandry and Dairying, in force since 2014, restructured in 2021 to run to 2025–26.

Objectives:

• Create and strengthen infrastructure for quality milk testing at farmer level.
• Expand procurement, chilling, processing and marketing of milk by cooperatives and producer companies.
• Build village-level cold chain, with priority for the North-East, hill areas and Union Territories.
• Train farmers and dairy staff in clean milk production.
• Raise returns to milk producers and create rural employment.

Components:

Component A, nationwide dairy development: new dairy cooperative societies and producer companies, bulk milk coolers and automatic milk-collection units, milk and product testing laboratories and adulteration-testing kits, processing and value addition, and training, awareness and monitoring.

Component B, dairying through cooperatives, implemented with NDDB and externally aided (JICA): strengthening of processing and feed plants, village-level institutions, productivity enhancement, and ICT and marketing support in selected states.

(c) Oestrus detection and time of insemination for better conception

Accurate detection and insemination timed to ovulation decide the conception rate.

Detection methods:

• Visual observation twice daily (dawn and dusk, 30 minutes each): standing to be mounted is the certain sign, with restlessness, bellowing, swollen vulva, clear elastic mucus, reduced milk yield and frequent urination. Silent heat is common in buffaloes and high yielders.
• Marking aids: tail chalk, tail paint, rump patches rubbed off on mounting, and chin-ball markers on teaser bulls.
• Teaser bulls or androgenised cows with aprons.
• Electronic devices: pedometers and activity or rumination collars that flag a rise in activity.
• Hormonal: milk or plasma progesterone assay (low in oestrus).
• Synchronisation: PGF2α given when a corpus luteum is present (cycle days 6–16) brings heat in 48–96 hours; Ovsynch or CIDR protocols allow fixed-time AI.

Body condition score of 3.0–3.5 improves expression of heat and conception.

Timing of insemination: ovulation follows onset of standing heat by about 24–32 hours in cattle (often later in buffalo), sperm need 4–6 hours for capacitation, and the ovum stays fertilisable for 6–12 hours. By the AM–PM rule, a cow first seen in heat in the morning is inseminated that evening, and one seen in the evening is inseminated next morning, which places sperm in the oviduct before ovulation. Buffaloes may need a slightly later window, and sexed semen is deposited later still because its fertile life is shorter.