Oestrus synchronization with short-term and long-term progestagen treatments in goats: the use of GnRH prior to short-term progestagen treatment

Abstract

The aim of the present study was to determine the efficacy of the synchronization of oestrus using short- and long-term progestagen treatments in Hair goats at the onset of the breeding season, and to evaluate the effect of the exogenous GnRH administration immediately prior to short-term progestagen treatment on the reproductive performance. A total of 75 Hair goats, aged 2.5-5 years-old were used in this experiment. Goats were divided equally into three groups (n=25 per group). Animals in LT-FGA (long-term progestagen treatment), ST-FGA (short-term progestagen treatment) and Gn-ST-FGA (GnRH-short-term progestagen treatment) groups received an intravaginal sponge (day 0) containing 30 mg fluorogestone acetate (FGA) for 14, 8 and 8 days, respectively, plus 75 μg cloprostenol i.m. 24 h before sponge removal and 400 I.U. equine chorionic gonadotrophin (eCG) i.m. at the time of sponge removal. In addition, the goats in the Gn-ST-FGA group received 10.5 μg busereline acetate i.m. at the time of sponge insertion (day 0). Oestrus response for all treatment groups was 100%. The mean interval from sponge removal and the onset of oestrus for the LT-FGA, ST-FGA and Gn-ST-FGA groups was 28.0±1.0 h, 28.83±1.1 h and 33.1±2.0 h, respectively. No significant difference in onset of oestrus among groups was recorded. The pregnancy rate, kidding rate, multiple kidding rates and litter size were 72.0, 61.1, 45.5% and 1.6 in the LT-FGA, 70.8, 76.5, 69.2% and 1.8 in the ST-FGA and 58.3, 78.6, 63.6% and 1.6 in the Gn-ST-FGA groups, respectively. The pregnancy rates were similar in the LT-FGA (72.0%) and ST-FGA (70.8%). However, the kidding rate, multiple kidding rates and litter size were numerically higher in the ST-FGA (76.5%, 69.2% and 1.8, respectively) group than in the LT-FGA (61.1%, 45.5% and 1.6, respectively) group. Although not statistically different, pregnancy rate and litter size was lower in the Gn-ST-FGA group (58.3% and 1.6, respectively) compared with the ST-FGA (70.8% and 1.8, respectively). In conclusion, it can be said that oestrus synhcronization with long-term progestagen treatment (14 d-FGA- PGF2α- eCG) could be replaced with short-term progestagen treatment (8 d-FGA-PGF2α- eCG) without a reduction in oestrus rate and fertility parameters in lactating goats at the beginning of breeding season. However, the use of GnRH prior to short-term progestagen treatment (8 d-FGAPGF2α- eCG) do not have a positive effect on fertility parameters in goats.

Keywords

• Gonadotropins, FGA, PGF2α, Oestrous synchronization, Goats.