Gonçalves Larissa de Paiva Nunes, Prado Alisson Jordão, Pacheco Aline, Almeida Yana Eliza Feitosa de, Baruselli Pietro Sampaio, Silva Welligton Conceição da, Minervino Antônio Humberto Hamad, Lima Jucelane Salvino de, Neves Kedson Alessandri Lobo
Postgraduate Program in Biosciences, Federal University of Western Pará (UFOPA), Santarem 68040-255, PA, Brazil.
Postgraduate Program in Animal Science, Federal University of Western Pará (UFOPA), Santarem 68040-255, PA, Brazil.
Vet Sci. 2025 Jan 8;12(1):27. doi: 10.3390/vetsci12010027.
We aimed to evaluate the reproductive efficiency of Nelore cows in fixed-time artificial insemination (FTAI) programs with early resynchronization. A total of 468 Nelore cows were divided into two experimental groups: R30-conventional resynchronization at 30 days ( = 234); R22-early resynchronization at 22 days ( = 234). Both groups followed a synchronization protocol using intravaginal progesterone devices combined with the administration of steroids and gonadotropins. The R30 protocol involved resynchronization 30 days after FTAI, while the R22 protocol implemented early resynchronization 22 days after FTAI without prior pregnancy diagnosis. In both groups, one FTAI was followed by two resynchronizations. The results showed similar pregnancy rates between the groups, with the pregnancy rate in the 1st FTAI being 50.85% in the R30 group and 48.72% in the R22 group ( = 0.742). During the 1st resynchronization, the rates were 45.22% in the R30 group and 46.67% in the R22 group ( = 0.742). The cumulative pregnancy rate after the 1st FTAI, 1st, and 2nd resynchronizations was 80.77% in the R30 group and 82.91% in the R22 group ( = 0.643), with no significant difference observed. Follicular dynamics were also monitored, with ovulation occurring in 78.95% of cases in the 1st FTAI, 91.67% in the 1st resynchronization, and 88.98% in the 2nd resynchronization. The mean diameter of the ovulatory follicle was 13.64 ± 3.48 mm, and the largest follicle diameter was significantly greater (14.47 ± 2.76 mm) in cows that ovulated compared to those that did not (11.54 ± 4.24 mm) ( < 0.05), reinforcing the association between follicle size and the likelihood of ovulation. These findings indicate that both early and conventional resynchronization protocols perform similarly, with early resynchronization offering advantages in reducing the calving interval. Furthermore, the relationship between follicular diameter and ovulation confirms the importance of follicle size as an indicator of reproductive success.
我们旨在评估进行早期再同步化的定时人工授精（FTAI）程序中内洛尔牛的繁殖效率。总共468头内洛尔牛被分为两个实验组：R30组——30天进行常规再同步化（n = 234）；R22组——22天进行早期再同步化（n = 234）。两组均遵循使用阴道内孕酮装置并结合类固醇和促性腺激素给药的同步方案。R30方案是在FTAI后30天进行再同步化，而R22方案是在FTAI后22天进行早期再同步化，且无需事先进行妊娠诊断。在两组中，一次FTAI后接着进行两次再同步化。结果显示两组之间的妊娠率相似，R30组第一次FTAI的妊娠率为50.85%，R22组为48.72%（P = 0.742）。在第一次再同步化期间，R30组的妊娠率为45.22%，R22组为46.67%（P = 0.742）。第一次FTAI、第一次和第二次再同步化后的累积妊娠率，R30组为80.77%，R22组为82.91%（P = 0.643），未观察到显著差异。还监测了卵泡动态，第一次FTAI中78.95%的病例发生排卵，第一次再同步化中为91.67%，第二次再同步化中为88.98%。排卵卵泡的平均直径为13.64±3.48毫米，与未排卵的母牛相比，排卵母牛中最大卵泡直径显著更大（14.47±2.76毫米）（P < 0.05），这加强了卵泡大小与排卵可能性之间的关联。这些发现表明，早期和常规再同步化方案的效果相似，早期再同步化在缩短产犊间隔方面具有优势。此外，卵泡直径与排卵之间的关系证实了卵泡大小作为繁殖成功指标的重要性。
