Effect of the Ovsynch protocol on ovarian changes and pregnancy rates after first insemination in lactating cows with or without puerperal metritis

The aim of this study was to determine how puerperal metritis affects pregnancy rates and ovarian changes in dairy cows synchronised with the Ovsynch protocol. The study included 72 cows, which were divided into two groups. Cows treated for puerperal metritis were defined as Group M (n = 34), and those without signs of puerperal metritis as Group H (n = 38). Cows were synchronised for the first artificial insemination (AI) on day 49 +/- 3 postpartum using a modified Ovsynch protocol. The number of cows that ovulated after the first injection of gonadotropin-releasing hormone (G1) was similar between Group H and Group M (36.84 and 23.53%, respectively; P > 0.05). At G1, the size of dominant follicles was smaller in healthy nonovulated subgroup (HNO) compared to metritic an-ovulated cows (MNO) (P < 0.05). Furthermore, the volume of corpus luteum was lower in the subgroup of metritic ovulated cows (MO) compared to healthy ovulated cows (HO) (P < 0.05). At the time of prostaglandin F2a treatment, progesterone (P4) levels in subgroups HO and MO were > 1 ng/ml, and they were different compared to subgroups HNO and MNO (P < 0.05). The study showed that at the time of the second injection of gonadotropin-releasing hormone (G2), follicle size was larger in Subgroup MO compared to Subgroup HO (P < 0.05). In conclusion, at the time of synchronisation, P4 concentration and luteal volume size was lower in metritic cows compared to healthy counterparts. However, pregnancy and embryo mortality rates were similar between metritic and healthy cows.