Conception rates following an Ovsynch and fixed-time insemination protocol with progesterone inclusion in cyclic dairy cows during the warm and cold seasons

Progesterone plasma levels during the warm period of the year (summer) are more variable and this can induce a reduction in the fertility of dairy cows. Therefore, the aim of this study is to investigate the effect of the combined use of progesterone supplements with an Ovsynch and FTAI protocol on conception rates during the summer in cows. The data were compared with treatments carried out during the cold season (winter). In total, 120 cows underwent oestrus synchronization by using an Ovsynch and FTAI protocol. After this, one group of 60 cows received progesterone supplements and another group of 60 cows did not. In each group, 30 cows were treated during the summer and 30 cows were treated during the winter. All cows were pre-synchronized with PGF2α 25 days and 11 days before starting the Ovsynch protocol. The conception rate at days 30 and 40 post-insemination was not changed by the Ovsynch protocol being supplemented with progesterone. No interaction between progesterone supplementation and the season (winter or summer) was observed (P=0.17). The results of the study indicate that in cyclic cows with a functional corpus luteum the supplementation of the Ovsynch-FTAI protocol with progesterone did not improve the conception rate during the warm or cold seasons.