Effects of prostaglandin F 2α treatment at follicular wave emergence on endometrial epidermal growth factor concentration on day 3 of the next estrous cycle and on fertility in dairy cows.

Inadequate exposure to estradiol (E ₂ ) and progesterone (P ₄ ) may be the main causes of altered endometrial epidermal growth factor (EGF) profile, leading to reduced fertility in dairy cows. We hypothesized that PGF _2α administration at different timings of the estrous cycle and stages of follicular development could change the profile of steroid hormones between luteolysis and estrus. This results in reduction in the peak concentration of endometrial EGF on day 3 (day 0 = estrus) in the next estrous cycle. In study 1, lactating Holstein cows were treated with PGF _2α either on days 12-14 (selection phase group, n = 20) or on days 16-17 (control group, n = 24) of the estrous cycle. Blood samples were obtained before PGF _2α treatment, 24 and 48 h after treatment, and on the day of estrus and ovulation for E ₂ and P ₄ assays. Endometrial tissues were collected by biopsy on day 3 for EGF assays. The duration from PGF _2α treatment to both estrus and ovulation was longer in the selection phase group than in the control group (P < 0.05). The time between estrus and ovulation was longer in the selection phase group (P < 0.05). E ₂ concentrations were higher in the control group on the day of estrus (P < 0.05). P ₄ concentrations were not different between the groups. Endometrial EGF concentrations were lower in the selection phase group than in the control group (P < 0.05). In study 2, lactating Holstein cows were treated with PGF _2α either on day 12 (selection phase group, n = 76) or day 16 (control group, n = 80). They were subjected to artificial insemination (AI) at estrus, and those that failed to ovulate by 24h after the first AI were subjected to second AI. On day 3, endometrial EGF concentration was determined. At estrus and on days 3 and 7, blood was collected for E ₂ and P ₄ assay from 20 randomly selected cows in each group before PGF _2α treatment. The cows in the selection phase group exhibited lower EGF concentration, proportion of cows with normal EGF profile, and conception rate than cows in the control group (P < 0.05). On the day of estrus, E ₂ concentrations tended to be lower in the selection phase group than in the control group (P = 0.08). P ₄ concentrations were not different between the groups. These findings suggest that low E ₂ concentrations at estrus and low P ₄ concentrations for a prolonged period due to premature termination of CL in the absence of a dominant follicle are potential causes of altered endometrial EGF profile in dairy cows.
Competing Interests: Declaration of competing interest The authors declare no conflicts of interest.
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