Effects of a reusable progesterone device on conception rates and estrus cycle re-synchronization in Nelore cows

Abstract

The objective of this study was to evaluate the reuse of an intravaginal progesterone (P4) device during diestrus of Nelore cow embryo recipients in order to improve conception rate, accelerate estrus cycle re-synchronization of non-pregnant animals, and reduce the amount of waste generated by animal breeding biotechnologies. Two experiments were performed using 268 multiparous Nelore cows. In experiment 1, all animals were subjected to a timed embryo transfer (TET) procedure, but at the time of embryo transfer, two treatment groups were established: T1 - the control treatment (N = 132) and T2 - animals receiving a second-use CIDR® device for 12 days (N = 136). Experiment 2 was performed on cows that had not remained pregnant after experiment 1 using two groups: G1 - a control group (N = 69) and G2 -re-synchronized cows that received a P4 device for 12 days for the first TET (N = 74). In experiment 1, no significant effect of the P4 treatment was observed on conception rate (T1 = 37.9%, T2 = 39.7%; P = 0.50) and corpus luteum (CL) diameter (T1 = 17.5 ± 3.4 mm, T2 = 18.1 ± 3.4 mm; P = 0.61). In experiment 2, no significant effect of the treatment was observed on conception rate (G1 = 22.2%, G2 = 35.7%; P = 0.24), recipients utilization rate (G1 = 75.4%, G2 = 70.3%; P = 0.86), and CL diameter (G1 = 17.4 ± 3 mm, G2 = 18.1 ± 3.2 mm; P = 0.27). However, the P4 treatment (for re-synchronization) significantly increased the conception rate (G1 = 22.2%, G2 = 35.7%; P = 0.04), which was similar to that in a conventional TET protocol performed with a new device (38.8%). We conclude that reusable intravaginal P4 devices can help accelerate TET protocols, suggesting an alternative application method; furthermore, this protocol may help reduce waste production in assisted animal breeding.