Reproductive performance of Creole goats subjected to estrus synchronization protocols differing in duration and GnRH administration

Abstract

Reproductive efficiency in goats is essential for improving productivity, with estrus synchronization and artificial insemination (AI) being strategic reproductive tools. Although post-AI GnRH administration has been proposed to improve luteal function and fertility, its effectiveness under different synchronization protocols in goats remains unclear. Therefore, this study evaluated the effect of GnRH administration five days after AI on the reproductive response of goats synchronized using short- and long-term protocols. A total of 39 Creole goats were distributed according to protocol type (short-term: n = 26; long-term: n = 13) and treatment (control: n = 18; GnRH: n = 21). In both groups, intravaginal sponges containing medroxyprogesterone acetate were inserted on Day 0. Artificial insemination was performed 64 h after device removal, and the depth of cervical semen deposition was recorded. Estrus expression was concentrated between 24 and 48 h after device removal in both protocols, with greater synchrony in the long-term protocol. No significant differences were observed in pregnancy rate between protocols (57.7 vs. 53.8%) or treatments (57.1 vs. 55.6%). Intermediate cervical semen deposition resulted in a greater pregnancy rate (69.2%) than superficial deposition (25.0%). Multiple correspondence analysis revealed associations between reproductive variability, insemination depth, and estrus expression patterns. In conclusion, neither post-AI GnRH administration nor protocol duration affected pregnancy rate. However, reproductive performance appeared to depend more on insemination-related factors than on hormonal treatments under field conditions in Creole goats subjected to cervical artificial insemination programs.