THE EFFECT OF DIETARY-PROTEIN ON REPRODUCTION IN THE MARE .3. OVARIANAND UTERINE CHANGES DURING THE ANOVULATORY, TRANSITIONAL AND OVULATORY PERIODS IN THE NONPREGNANT MARE

In the main experiment the total daily protein intake and quality (ess ential amino-acids) was varied in 4 groups of mares. The incidence of oestrus in mares during the transitional period was unaffected by prot ein nutrition. Ovarian activity, as evaluated by follicular developmen t and size of the ovaries, was affected. Mares that received low-quali ty protein (Groups 1 and 2) had a higher number of smaller follicles ( < 10 mm) that developed during the transitional period compared to mar es on a high-quality protein intake (Groups 3 and 4). The mares that r eceived the high quality protein ovulated 2-3 weeks earlier in the bre eding season in a synchronised period of 4-5 weeks compared to a perio d of 6-8 weeks in Groups 1 and 2. The duration of the subsequent oestr ous cycles was not affected. There was no difference in the diameter o f the largest follicle of mares between groups on the day before ovula tion. In a separate experiment, 5 maiden Anglo-Arab mares, 4-5 years o f age, were slaughtered at different stages during the anovulatory, tr ansitional and ovulatory periods of the breeding cycle. The morphology of the ovaries and uteri of these mares was described and photographe d for use as guidelines when comparing ovarian changes and follicular activity of mares.