Abstract
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 30µg 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.
Highlights
Depending on latitude and breed goats are seasonal breeders
The use of progestagens is under review in some countries, due to issues related to public health and animal welfare
Previous studies in goats had associated the use of Human chorionic gonadotropin (hCG) to induction acessory corpus luteum, induction of estrus (Fonseca et al, 2006), and to overcome the negative effect of premature regression of corpora lutea after superovulatory treatment (Saharrea et al, 1998)
Summary
Depending on latitude and breed goats are seasonal breeders. The brazilian territory consists of a wide variety of latitudes (5o16’N to 33o45’S), strongly or weakly influencing goat reproduction. In Southeastern Brazil, commercial dairy systems using specialized dairy breed regularly must induce or synchronize estrus in order to obtain a good amount of milk throughout the year. A combination of progestagens, gonadotropins and prostaglandins is the most used program to induce estrus (Souza et al, 2011). We have demonstrated previously that estrus can be efficiently synchronized in Alpine and Saanen breeds using two doses of cloprostenol 10 days apart during the breeding season (Fonseca et al, 2012)
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