Resynchronization of ovulation with new and reused intravaginal progesterone-releasing devices without previous pregnancy diagnosis in Bos taurus indicus cows subjected to timed-artificial insemination.

Abstract

The study aimed to evaluate pregnancy per artificial insemination (P/AI) of cows subjected to synchronization and resynchronization in ovulation protocols using intravaginal progesterone-releasing insert (P4) before pregnancy diagnosis (PD) and the relationship of PR with the diameter of preovulatory follicles (ØPOF) before TAI. Cows (n=378) were distributed into two groups: a resynchronization group with new devices (GRN; n=185) and resynchronization group with used devices (GRU; n=193). On Day 0, both groups received a new P4 and estradiol benzoate (EB). On D8, P4 removal+D-cloprostenol+eCG+estradiol cypionate (EC) was done. On d10, TAI was conducted. On d32, cows were resynchronized and divided into two groups, GRN (n=185) and GRU (n=193). The GRN group received a new P4+EB, and the GRU group received a used P4+EB. On d40, the P4 was removed+PD. The non-pregnant cows received D-cloprostenol+eCG+EC. US was done again on d42 to determine ØPOF before the second TAI. The P/AI of the GRN and GRU groups after synchronization were 56.2% and 57.0% (p=0.87), respectively, and those after resynchronization were 58.0% and 37.3% (p<0.008), respectively. The P/AI of the GRN and GRU groups observed after TAI (synchronization+resynchronization) were 81.6% and 73.1%, respectively (p=0.047). No difference (p=0.067) in ØPOF between the pregnant and non-pregnant cows in the GRN was found, whereas the GRU group showed a significant difference (p=0.003). Resynchronization protocols optimized the P/AI in both groups. New intravaginal devices resulted in greater P/AI and P/AI accumulation in resynchronization as compared with the GRU; the ØPOF was related with P/AI.