(a) Describe the cellular and fluid constituents of semen in domestic animals. (20 marks) (b) Describe the scientific management…

(a) Cellular and Fluid Constituents of Semen

Semen is a complex biological fluid comprising cellular elements and seminal plasma, essential for fertilization and sperm survival. The cellular constituent is the spermatozoon, which consists of three distinct parts: the head, midpiece, and tail. The head contains the nucleus with genetic material and the acrosome, a cap-like structure rich in hydrolytic enzymes (hyaluronidase, acrosin) required to penetrate the zona pellucida. Head shape varies by species: it is flat and paddle-shaped in the bull, ram and boar, but long and cylindrical in the cock. The midpiece houses mitochondria arranged in a helical pattern, providing ATP for motility. The tail (flagellum) facilitates propulsion. Sperm abnormalities are classified as primary (developmental defects like double heads or coiled tails) or secondary (post-formation damage like detached heads, bent tails or distal cytoplasmic droplets), both reducing fertility.

The fluid fraction, seminal plasma, is secreted by accessory glands: seminal vesicles, prostate, and bulbourethral glands. In bulls, seminal vesicles contribute the bulk of volume and fructose, the primary energy substrate for sperm metabolism. Citric acid acts as a buffer and chelator, while prostaglandins induce uterine contractions. In rams, fructose is also the principal sugar in seminal plasma, supporting sperm motility, with smaller amounts of sorbitol. Enzymes such as acid phosphatase (prostatic origin) and alkaline phosphatase are markers of glandular health. In boars and stallions the ejaculate is fractionated into sperm-rich fractions (high sperm density, low fructose) and sperm-poor fractions (low sperm density, high fructose and enzymes). The plasma provides nutrients, buffers, and immunoprotection, while its decapacitation factors prevent premature capacitation—the physiological modification of sperm required for fertilization, which occurs in the female tract.

(b) Scientific Management of Dairy Cows Post-Parturition

Post-partum management focuses on calving hygiene, uterine health, metabolic stability, and lactation. The calf receives colostrum within the first hour, the cow's udder and hindquarters are washed, and she is offered lukewarm water with bran and kept in a clean, dry, well-bedded calving pen. After calving, the placenta should be expelled within 12–24 hours; retention beyond 24 hours requires veterinary intervention to prevent metritis. Uterine involution is monitored via rectal palpation and ultrasonography to ensure the uterus returns to pre-pregnancy size by 40–60 days. Lochial discharge is tracked; normal lochia transitions from bloody to serous to mucoid over 2–3 weeks. Abnormal discharge (foul smell, purulent) indicates endometritis, treated with antibiotics or intrauterine infusions.

Metabolic challenges are critical during the transition period. Parturient paresis (milk fever) is prevented by dietary calcium management, such as low-calcium pre-calving diets or anionic salts (negative DCAD diets). Subclinical ketosis is managed by monitoring beta-hydroxybutyrate (BHB) levels and providing adequate energy-dense rations. Mastitis prevention involves strict hygiene during milking, dry cow therapy, and teat dipping. Nutritionally, cows enter negative energy balance; gradual increase of concentrates prevents acidosis. Peak yield comes around 6–8 weeks, so concentrate is matched to yield (roughly 1 kg per 2.5 kg of milk above maintenance in cows) and daily milk recording tracks the lactation curve. Reproductive readiness is assessed before first service (typically 60–90 days post-partum) via estrus detection or timed AI, ensuring the cow has recovered body condition and uterine health.

(c) Feeding of Ewe Flock During Gestation and Suckling

Gestation feeding is phased to match fetal growth. In early gestation (first 8 weeks), ewes require maintenance nutrition as fetal growth is slow. Mid-gestation (weeks 9–12) sees moderate nutrient demand. The critical phase is late gestation (last 4–6 weeks), where 70% of fetal growth occurs. Steaming-up is employed here, providing 0.5–0.75 kg of concentrate per head per day to prevent pregnancy toxaemia and enhance colostrum production, directly impacting lamb birth weight and survival.

During the suckling period, nutrient demands peak due to milk production. Ewes require high-energy rations to maintain body condition score (BCS) between 2.5 and 3.0, preventing excessive weight loss. Creep feeding for lambs begins at 2–3 weeks of age, introducing starter pellets to stimulate rumen development and weaning readiness. Clean water ad libitum and a mineral mixture with salt are provided throughout, with extra calcium in late pregnancy. In accelerated lambing systems, flushing (a raised plane of nutrition for 2–3 weeks before rejoining the ram) improves ovulation rate for the next mating, which matters in Indian smallholder flocks where feed resources are often limited.