Breeding, Reproduction and Improvement of Livestock
Reproduction basics
The exam tests the oestrus cycle, heat detection, artificial insemination timing, gestation length and breeding systems for improvement. Buffaloes are a common source of error because their heat signs are subtle.
Core rules and concepts
- Oestrus cycle: about 21 days in cattle and buffalo; heat duration roughly 12–18 hours in cattle and often 24–48 hours in buffalo.
- Ovulation occurs after heat; AI is usually done about 12 hours after standing heat, with a second dose if heat persists.
- Gestation: about 280–285 days in cattle and 310–315 days in buffalo.
- AI uses frozen semen stored in liquid nitrogen at about −196°C; thawing and insemination must follow protocol.
- Improvement methods: selection, progeny testing, crossbreeding and grading up. Inbreeding should be avoided.
- Record heat dates, AI dates and calving dates to calculate expected calving and detect repeat breeders.
Worked example
A cow is seen standing to be mounted at 7 a.m. on 1 June. AI is planned for the evening of 1 June or the morning of 2 June, about 12 hours after standing heat. Expected calving is around 280–285 days later, in mid-March. The reasoning links heat timing to ovulation and then to gestation length.
Traps that cost marks
Do not inseminate a buffalo only because she is quiet; silent heat is common. Do not use cattle gestation for buffalo. Do not inseminate long after heat ends. Do not ignore repeat breeding. Do not confuse grading up with crossbreeding.