Evaluation of different hormonal treatments on oestral and ovarian responses in Moroccan Beni Arouss goats during anoestrus and breeding season.

Abstract

The efficacy of eight combinations of fluorogestone acetate (FGA, 20 or 40mg as intravaginal device during 11days), equine chorionic gonadotropin (eCG, 300 or 500UI injected 48hr before FGA removal) and prostaglandin F2α (cloprostenol, 0 or 50μg injected 48hr before FGA removal) aiming at induction and synchronization of oestrus and ovulation was evaluated during the anoestrus season in spring and during the breeding season in autumn in adult Beni Arouss goats. Oestrous behaviour was recorded between 12 and 60hr after FGA removal. Blood samplings allowing to assess onset of the pre-ovulatory LH surge and increase of progesterone as sign of an active corpus luteum were performed, respectively, between 20 and 60hr and 3, 5, 8 and 15days after FGA removal. No season-related differences (spring vs. autumn) were observed for oestrous response (95% vs. 93%), pre-ovulatory LH surge (94% vs. 84%) and luteal response after 3-8 and 11-15days post-treatment (respectively 92% vs. 66% and 92% vs. 98%). The onset of oestrus (21 [13-53] vs. 32 [12-54]hr) and LH surge (26 [20-60] vs. 38 [22-60]hr) occurred significantly later in autumn. FGA (40 vs. 20mg) in autumn significantly delayed the onset of oestrus (36 [16-54] vs. 23 [12-47]hr) and LH surge (44 [26-58] vs. 33 [22-60]hr). Significant treatment-related differences were recorded for onset of LH surge (earliest for 20mg FGA, 300IU eCG, 50μg PGF2α ) and onset of luteal phase (latest for 40mg FGA, 300IU eCG, 50μg PGF2α ). In conclusion, the hormone combinations tested appeared equally effective in terms of oestrous and ovulation rates. Season has influenced significantly the onset of oestrus and LH surge, and the high dose regimen of FGA delayed the ovarian response in autumn.