Effects of Two Hormonal Protocols for FTAI on the Fertility of Repeat Cows

This study, carried out from January to July 2022 in three provinces of Ecuador, aimed to evaluate the effect of two hormonal protocols for fixed-time artificial insemination (FTAI) on the follicular dynamics, hormonal profile and fertility of dairy cows affected by repeat cow syndrome (RCS). Two groups of Holstein cows with RCS were formed, G1 (conventional) and G2 (J-Sinch), with 26 and 24 animals, respectively. Gynaecological examinations and hormonal determinations in blood serum were carried out. Follicular diameter and concentrations of FSH, LH and P4 were compared by <i>t</i>-Student test for independent samples, estrus and pregnancy were compared by binomial comparison of proportions, and factors associated with pregnancy were determined by a model of logistic regression (LR). In G1, the diameter of the dominant follicle was greater (<i>p</i> < 0.05) in the left ovary on day 7 following intravaginal device implantation. However, it was similar (<i>p</i> > 0.05) in the right ovary on days 7, 8 and 9. The estradiol and LH concentrations at the time of FTAI and the P4 concentrations 15 days after FTAI, as well as the pregnancy rate, were higher in G1 (<i>p</i> < 0.05). The LR model explained 60.91% of pregnancies (<i>p</i> < 0.001), and the concentrations of estradiol, LH and P4 and the absence of estrus at the time of FTAI had an influence on the pregnancy rate (<i>p</i> < 0.05). It was concluded that the inclusion of estradiol benzoate increased the dominant follicle diameter and the concentrations of estradiol, LH and P4 and the pregnancy rate at the first FTAI.