The Oestrus Cycle (or Estrous Cycle) is the recurring reproductive cycle of most female mammals — determining when they are sexually receptive and fertile. It is a key topic in Class 12 Biology (Reproduction chapter).
Cattle farmers closely track the oestrus cycle (21-day cycle in cows) to optimise conception — either through natural mating or artificial insemination (AI).
The oestrus cycle is the cyclical reproductive pattern in non-primate female mammals (like cows, dogs, cats, rats, and sheep). It consists of hormonal, physiological, and behavioural changes preparing the female for mating and pregnancy.
The term 'oestrus' (from Greek 'oistros' meaning frenzy) specifically refers to the fertile period when the female is receptive to mating.
| Feature | Oestrus Cycle | Menstrual Cycle |
|---|---|---|
| Occurs in | Non-primate mammals | Primates (humans, apes) |
| Fertile period | Oestrus (heat) | Around ovulation (day 14) |
| Uterine lining | Reabsorbed | Shed (menstruation) |
| Sexual receptivity | Only during heat | Can occur anytime |
| Duration | Varies (cow: 21 days) | ~28 days (human) |
'Heat' is the colloquial term for the **oestrus phase** — the period when a female animal is sexually receptive and fertile. A dog in heat, for example, is in her oestrus phase.
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