Oestrus Synchronization in Merino Sheep Using Intravaginal Sponges, Estrumate and PMSG on Oestrus Activity

Abstract

A study was conducted with 204 Merino ewes as experimental units to assess the effectiveness of four estrus synchroni-zation protocols. The ewes were divided into four groups: TRT A (Control), TRT B (Intravaginal sponges for 12 days), TRT C (Double prostaglandin injections on days 0 and 11) and TRT D (Intravaginal sponges for 13 days, a single prostaglandin injection on day 12, plus PMSG on day 13). Six rams were used to detect heat, with standing to be mounted as the primary indicator of estrus. There were no significant differences (p>0.05) in estrus response rates among the groups: 94.10% for TRT B, 96.20% for TRT D, and 90.20% for both TRT A and TRT C. Additionally, the time from treatment withdrawal to the onset and end of estrus showed no significant variation (p>0.05). The duration of estrus differed significantly among the treatments (TRT D, TRT A, and TRT C) with notable differences
at specific time intervals: 48h and 36h for TRT D, and 24h for TRT C (p<0.05). Significant differences were also found between TRT B and TRT D at 48h and 60h post-treatment withdrawal. Additionally, TRT D showed high significance at 24h and 36h intervals. At 72 hours, both TRT C and TRT D were significant, with TRT D remaining significant at 84h (p<0.05). Overall, combination treatment (TRT D) was more effective in synchronizing estrus in Merino ewes, resulting in a higher response rate and shorter interval from treatment withdrawal to estrus onset.