RESUMO
The goal of this study was to assess the efficacy of the re-utilization of an ear implant impregnated with norgestomet on estrus synchronization response and pregnancy rates in sheep. Fifty-five Texel ewes were classified according to body condition (3.5) and live weight (65 kg), and randomly assigned to two experimental groups: NORN-new (n = 30) and NORU-used (n = 25). The dose of norgestomet used in the treatments was half of that recommended for bovine (1.5 mg). The synchronization protocol consisted of an ear implant inserted on day 0 (beginning of the experiment) and kept for 6 days. The removal of the implant on day 6 was followed by an injection of a prostaglandin analogue (0.263 mg) and eCG (250 IU). Rams with paint applied to their chest were used to facilitate estrus detection for 5 days following implant withdrawal. Estrus behavior was observed in 93.3% (28/30) and 90% for NORN and NORU, respectively. Pregnancy rates for NORN were 73.3% and for NORU were 68%. Estrus behavior and pregnancy rates between treatment groups did not differ statistically. Therefore, the re-utilization of ear implants impregnated with norgestomet, in addition to eCG and a prostaglandin analogue in short-term estrus synchronization protocols, allow acceptable estrus response and pregnancy rates in sheep.
