Animal Breeding, Genetics and Reproduction
Animal breeding, genetics and reproduction tests inheritance, selection, AI, estrus detection and reproductive cycles in cattle, buffalo, sheep, goat and pig. Punjab questions often stress buffalo reproduction because silent estrus and long calving intervals are common field problems.
Core rules
- Cow estrous cycle about 21 days (18–24), buffalo about 21–22; standing estrus is shorter in buffalo and often silent. Ovulation occurs after estrus ends; AI timing should follow detection.
- Gestation: cow about 280 days, buffalo about 310, sheep about 148, goat about 150, pig about 114.
- Selection response R = h² × S. Heritability h² is population-specific; high h² traits such as milk yield respond faster than low h² traits such as fertility.
- Crossbreeding exploits heterosis but needs a planned grading-up programme. Inbreeding raises homozygosity and exposes recessive defects.
- AI requires correct semen handling: thaw at recommended temperature, deposit in body of uterus, record heat and insemination.
Worked example
A herd has h² for 305-day milk yield = 0.30. Selected parents average 100 kg above herd mean. R = 0.30 × 100 = 30 kg expected genetic gain per generation. Reasoning: only the heritable fraction of the selection differential is transmitted; the rest is environmental. A trait with h² 0.05 would give only 5 kg.
Traps
Do not time AI by the calendar alone; use observed estrus. Do not confuse heritability with repeatability. Do not assume crossbreds are always superior-management and adaptation matter. Do not ignore the postpartum period: uterine involution and negative energy balance affect conception.