Cow Ovulation Cycle

The average time of ovulation was 13 57 0 68 hours from the end of estrus.

Cow ovulation cycle. The first part of the cycle is called the follicular phase. Ovulation takes place approximately 30h after the onset of oestrus and after the behavioural signs of oestrus have ceased. This first half of the cycle can differ greatly for each woman lasting anywhere from 7 days to 40 days. This phase starts the first day of the last menstrual period lmp and continues until ovulation.

The estrous cycle of the cow is generally about 21 days long but it can range from 17 to 24 days in duration. During the heat cycle the follicle matures and the side opposite of the egg bulges and becomes thin. One cow an angus ovulated on two occa sions before she went off estrus. Progesterone is the hormone of pregnancy and is produced in the ovary by the corpus luteum or cl while oestrogen is the main hormone responsible for oestrus heat behaviour and is produced in the ovary by the follicle from which the egg comes.

Traditionally considered as day 0 of a new cycle the dominant follicle reaches its maximum growth matures and ovulates. Normal cl lifespan takes up 14 18 days of the typical 21 day estrous cycle of a beef cow. Ovulation is the process where an ovum or egg ruptures from a mature follicle. The two main hormones are progesterone and oestrogen.

Ovulation was found in all except three instances to occur within the first day after the end of estrus. Another angus ovulated 26 hours after the end of estrns. Ovulation is induced by high lh concentrations preovulatory lh peak. Estrous cycles give a heifer or cow a chance to become pregnant about every 21 days.

The ovulation cycle divided into two parts. The first ovulation postpartum often occurs without visual signs of the cow being in heat and is of ten followed by abnormal function of the corpus luteum cl. The patterns of the two main hormones of the cow s oestrus cycle are shown in figure 3.