Effects of body condition change over oestrus, follicular development and ovulation rate in Pelibuey ewes under tropical conditions
In order to study the effect of changing body condition on the oestrus, follicular development and ovulation rate, twenty two Pelibuey ewes were divided in two groups of High Body Condition (HBC>L) and Low Body Condition (LBC>H). The ewes were evaluated over an oestrus cycle at the initial body condition, and during a seven week period, the HBC>L group received a diet with half and the LBC>H with double of their maintenance energy requirements to induce a change in body condition. A second oestrus cycle was evaluated at the end of seventh week, at the final stage of change, when both groups reached a similar body condition. Before each oestrus cycle evaluated, ewes were synchronized and the oestrus detected. The oestrus length, oestrus cycle length and the follicular populations of small, medium and large follicles were estimated. Ovulation rate was determined nine days after the oestrus. There were no differences in both groups in oestrus length and oestrus cycle length (P>0.05). The maximum follicular size was similar in both groups (P>0.05). The mean number of follicles that attained a diameter > 4 mm was higher in CCB>A ewes when gaining body condition, compared to their previous one (P<0.05), however, it was similar in CCA>B group before vs. during the loss of body condition. There was no difference in ovulation rate in both groups, before vs. during the change of body condition (P>0.05). It is concluded that Pelibuey ewes in low or high body condition, that gain or lose body condition and reach a similar body condition (medium), have no differences in oestrus length, oestrus cycle length and maximum follicular size, but showed differences in the number of large follicles reaching an ovulation size in ewes gaining body, which doesn't mean an improvement in the ovulation rate.