Effect of urea in the diet on ovarian follicular dynamics and plasma progesterone concentration in Alpine goats

To evaluate the effect of using urea in the diet on ovarian follicular dynamics and plasma urea and progesterone concentration, an experiment was carried out with 29 Alpine goats randomly distributed into four diets, each one containing 0%; 0.73%; 1.46% or 2.24% of urea on total dry matter. The follicular dynamics was monitored daily by ultrasonography. The estrous cycles were characterized by occurrence of two, three, four or five follicular waves. The emergence day of the first follicular wave in cycles with two waves, the length of the third wave and the maximum diameter of the largest follicle of the third wave in cycles with three waves presented a quadratic behavior according to the percentage of urea in the diets. In cycles with four waves, the urea intake did not influence the follicular dynamics. The interestrus and interovulatory periods and the luteal and follicular phases length did not differ among treatments. The plasma urea concentration did not differ among diets neither among collection weeks. Plasma progesterone concentration on the estrus day and on the 11th day after estrus presented quadratic behavior, and on the 15th day after estrus, it linearly reduced acording to the percentage of urea in the diets. The supply of urea in diets at levels up to 2.24% in dietary dry matter did not influence the dry matter intake and the urea plasma concentration. For goats, the emergence day and the length of the waves, the follicular diameter and the plasma progesterone concentration on the estrus day and in the latter stages of diestrus were altered when there was supply of urea in the diet.