THE INFLUENCE OF OVARIAN STATUS ON RESPONSE TO ESTRUS SYNCHRONIZATIONTREATMENT IN DAIRY GOATS DURING THE BREEDING-SEASON

The influence of ovarian status (presence of a corpora lutea and folli cles) on the times of the onset of estrus, LH peak and ovulation rate at a synchronized estrus was evaluated in 73 Alpine and Saanen cyclic goats. Does were treated for 11 d with 3 mg norgestomet implants or 45 mg fluorogestone acetate (FGA) sponges. They also received 400 IU of P MSG and 50 mu g of a PGF(2 alpha) analog on Day 9 of progestagen primi ng. Follicles (1 to 7 mm) and corpora lutea (CL) were counted by lapar oscopy on Days 0 and 9 of progestagen treatment and 5 or 6 d after the synchronized estrus. Estrus was detected every 4 h from 16 to 60 h af ter the end of progestagen treatment using a vasectomized buck. The LH concentration was determined by radioimmunoassay (RIA) in blood sampl es collected every 4 h for 24 h beginning at the time of the onset of estrus. The number of follicles on Days 0 and 9 of progestagen treatme nt was not related to the time of the onset of estrus and occurrence o f the LH peak or to ovulation rate. The number of CL on Day 9 influenc ed the time of occurrence of the LH peak but not the time of the onset of estrus. Thus, in does with 2 or 3 CL on Day 9, the LH peak occurre d at 46.9 h after the end of progestagen treatment, and in does with 1 or 0 CL at 42.2 and 42.5 h, respectively, after treatment, suggesting that the number of CL at luteolysis is a factor in the variability of response after the synchronization of estrus.