Effect of synchronization protocols and GnRH treatment on the reproductive performance in goats

Abstract

Experiment 1 was designed to determine if the estrous response and pregnancy rates differ between two synchronization protocols (Ovsynch vs two PGF2α injections, 10 days apart), in Beetal and Dwarf does. The Ovsynch group of goats (n=14) received an intramuscular injection of a GnRH analogue (12.5μg lecirelin) on day 0 and a treatment of a PGF2α analogue (37.5μg d-cloprostenol), on day 7 – followed by a second injection of the GnRH analogue 48h later (day 9). The double PGF-treated goats (n=14) received two intramuscular injections of a PGF2α analogue 10 days apart. The estrous response did not differ significantly between the regimes (Ovsynch 71%; double PGF 100%). Further, the interval from standing estrus to ovulation (24±3.7h vs 30±2.7h), ovulatory diameter (7.1±0.2mm vs 7.0±0.2mm), pregnancy rate (60% vs 78%) and fecundity (1.6±0.5 vs 1.6±0.7) was not significantly different between the Ovsynch and PGF treatment groups. The objective of Experiment 2 was to determine if the administration of GnRH at the time of natural breeding increases the pregnancy rate in Beetal goats. Goats were randomly allocated to two groups (GnRH, n=11 and Control, n=14). The GnRH-treated does received 12.5μg lecirelin on the day of natural breeding, while the control does received no treatment. The interval from standing estrus to ovulation (31.2±2.9h vs 36.0±5.3h; P>0.05), ovulatory follicle diameter (6.7±0.1mm vs 7.2±0.5mm; P<0.05), pregnancy rate (54% vs 64%; P>0.05) and fecundity (1.5±0.5 vs 1.7±0.5; P>0.05) were evaluated for the GnRH and control does, respectively. It could be concluded that the Ovsynch treatment appeared to be similar to the double PGF protocol in terms of the reproductive response. However, this needs to be tested on a larger herd size. Furthermore, it would seem that the use of GnRH at the time of breeding also did not significantly improve the reproductive rate in goats.