Oestrous cycle - interval between two oestrous Ovulation - shedding of eggs by the ovary in the female Ejaculation- shedding of sperms in the vagina by the male Fertilization - union of the sperm and egg in the female reproductive tract Conception - union of the fertilized egg unto the wall of the uterus (placentation) Pregnancy o r Gestation - period of development of the foetus in the uterus or womb Parturition – act of giving birth
TIME OF MATING Heifers should be at least 18 months old at the time of first mating. The heifer or cow will accept the bull during the oestrus period or heat. This period lasts for about 12- 24 hours. At the time of oestrus, the animal exhibits both physical and behavioural changes. These changes are:
restlessness
bellowing
mounting other animals and also allowing herself to be mounted
loss of appetite
swelling and reddening of the vulva
milk production in lactating animals decreases.
During the oestrus period, ovulation takes place about 12 hours after standing heat. The best time for mating the cow is about 10 hours after the end of standing heat i.e. if heat begins in the morning, the farmer should breed in the evening. If it begins in the afternoon, breeding should be done the next morning. It is during this time that conception is likely to take place. If the animal is not mated during oestrus, or if conception does not take place, the cow will return into heat/oestrus within 18-21 days. This period between one oestrus and the next is the oestrus cycle. 98