Fertility in dairy cows treated in the early luteal phase with a reused progesterone-releasing intravaginal device

Abstract

In this study, we tested whether early luteal phase  treatment with a previously used progesterone-releasing intravaginal device (DIV) increased conception rate (CR) in dairy cows. Two experiments were performed; in the first, progesterone concentrations were determined in cows treated with a reused DIV. Seven cows received PGF2a and a reused DIV was inserted for seven days. Blood samples were collected daily for progesterone determination. Progesterone increased from 0.42 ± 0.17 ng/mL (mean ±  standard deviation) at DIV insertion to 1.99 ± 0.52 ng/mL at  24 h and 2.11 ± 0.40 ng/mL at 48 h after; during the  treatment period, progesterone showed an average  concentration of 1.4 ± 0.55 ng/mL. In the second  experiment, 383 cows were randomly divided on day 4 post-insemination, into two treatment groups: DIV (n = 188), received a reused DIV, which was removed on day 14;  control (n = 195), did not receive DIV. Progesterone  concentrations were determined in seven cows from each group. The CR was not affected by treatment [DIV (33.5 %)  vs. Control (37.4 %); P > 0.05]. No interaction was observed between treatment and service number, parity, the type of postpartum (normal or pathological), body condition, or  days in milk (P > 0.05). Progesterone concentrations were similar between treatments (P > 0.05). We conclude that the insertion of a reused DIV at early diestrus did not increase serum progesterone concentrations or conception rate in dairy cows.