Reproductive parameters of dairy goats submitted to estrus synchronization with prostaglandin F2α associated or not to hCG at estrous onset

The objective of this study was to evaluate the efficiency of two doses of PGF associated or not to hCG on the associated reproductive parameters in dairy goats. A total of 29 goats received two doses of 30 mu g d-cloprostenol latero-vulvar at a 10 day intervals (Day 1 and Day 10). The does were allocated according to body weight and body condition score into two treatments, to receive hCG (250IU) or saline at estrus onset. After the second dose of PGF, estrus was monitored and ultrasound exams were performed twice daily. All does were inseminated 16h after estrus onset. Blood collection was performed every day for progesterone assay. The use of hCG at estrus onset did not affect any studied parameter and therefore the data were pooled. Estrous response rate was similar (P>0.05) after the first (75.9%, 22/29) and the second dose of PGF (79.3%, 23/29). The interval between the administration of PGF and estrus onset was greater (P<0.05) after Day 1 (75.8 +/- 53.9h) than Day 10 (47.7 +/- 10.1 h). Estrus duration was superior (P < 0.05) after Day 1 (35.4 +/- 15.9h) to Day 10 (26.8 +/- 15.0h). Ovulation rate was 79.3% (23/29) after the second dose of PGF. No differences (P>0.05) between both experimental groups were detected in the following parameters, averaging: the interval from the second dose administration to the ovulation (86.6 +/- 11.4h), interval from estrus to ovulation (39.9 +/- 12.3 h), diameter of largest follicle (7.2 +/- 1.4) and number of ovulations (1.8 +/- 0.6). At Day 1, 52.4% (11/21) of does presented progesterone concentrations <1ng/mL. At Day 10, 100% of the animals presented concentrations >1ng/mL. The results of the present study indicate that estrus can be efficiently synchronized in dairy goats with the use of two doses of PGF at a 10 day interval. Further research should be done evaluating hCG use in different doses or moments of administration.