The experimental objective was to evaluate the effect of human chorionic gonadotropin (hCG) administration on pregnancy rate and gestation length and on serum concentration of progesterone (P4) in Alpine (83) and Saanen (60) dairy goats induced by artificial photoperiod to enter the breeding season. Animals were randomly allocated to two treatments following estrus: in treatment 1 (T1) goats received 1ml saline solution and in treatment 2 (T2) animals received 250IU of hCG in 1ml saline intramuscularly during the third day after estrus. Pregnancy rates detected by ultrasound technology 35 days after mating did not differ significantly between treatments (P>0.05). They equaled 80.4 and 70.3% for Alpine goats and 72.7 and 81.5% for Saanen goats in T1 and T2, respectively. Overall pregnancy rates were 77.2% and 75.0% for the controls and treated animals, respectively. Gestation length was not affected by the hCG treatment. Blood samples were collected from 5 Alpine does from each treatment the day of estrus (day 0) and on days 3, 8, 15, 21, 42 and 60 after estrus, for determination of progesterone concentration in plasma. Means were 5.84 and 5.76ng/ml for the control and treated does, respectively, and were not affected by treatment (P>0.05), although concentrations did differ among collection days (P<0.05). The administration of hCG the third day after estrus did not affect pregnancy rate or P4 concentration and had no beneficial effect on reproduction in the does.
goat; pregnancy; estrus; hCG; progesterone