Nutrition and ovarian activity of mares early in the breeding season.

Abstract

The length of the oestrous cycles, the size and activity of the ovaries, and the time and incidence of ovulation early in the breeding season of mares kept on veld grazing (Group A) were compared with those of mares which received a supplementary diet of concentrates and lucerne hay (Group B). more or less constant against a marked increase in body mass in Group B. All the mares in Group B came into oestrus and ovulated within a period of 43 days. In Group A only 25% of the mares ovulated, while 25% remained in anoestrum. The remaining 50 per cent came on heat but did not ovulate during the 53-day experimental period. A marked difference in ovarian activity between the two treatment groups was noticeable.