Comparison of the CoSynch Protocol with and Without the Addition of Progesterone and eCG on the Pregnancy Rate and Follicular Diameter in Bos indicus Heifers

The IATF is a biotechnological tool that allows the control of the estrous cycle of the female through the incorporation of hormonal compounds that specify the exact moment of heat and ovulation. The combination of these compounds has allowed the emergence of countless hormonal protocols that seek to improve synchronization. The objective of this study was to evaluate the use of GNRH-based hormonal protocols on the fertility of Bos indicus heifers. A total of 180 clinically healthy Brahman heifers (cyclic and acyclic) with a body condition score of four were synchronized. The experimental treatments corresponded to three protocols that included the following hormones: GNRH-PGF2-GNRH (T1-T2), DIB-GNRH-PGF2-GNRH (T3-T4) and DIB-GNRH-PGF2-eCG-GNRH (T5 and T6). The animals were evaluated for preovulatory follicle size and pregnancy diagnosis by means of ultrasonography using an ALOKA Co., Ltda. UST-5820-5 ultrasound machine equipped with a 5MHz linear translator, the screen was divided into 2B mode, the The image was frozen with the Freeze option. With the synchronization protocols, a total pregnancy rate of 10.7% (T1), 16.6% (T2) 36.8% (T3) 41.9% (T4) was obtained. 38.7% (T5) and 27.68% (T6). An effect (P= 0.0803) was found between the treatments when comparing pregnancy proportions, it was found that T 1 and T 2 were statistically equal (p>0.05). The same happened with treatments T6, T3, T5 and T4, but differences (p <= 0.05) were found between treatments T1 and T2 when compared with Treatments T6, T3, T5 and T4. There were no differences (P >= 0.05) in the average preovulatory follicle size, these being 10.28, 11.21 and 11.77 mm for heifers synchronized with treatments 1, 2 and 3 respectively. The use of the GnRH hormone in combination with progesterone in the Cosynch protocol significantly improves pregnancy rates in Bos indicus heifers, compared to the traditional Cosynch protocol.