Potential relationship between normalization of endometrial epidermal growth factor profile and restoration of fertility in repeat breeder cows

The present study characterized alterations of the endometrial epidermal growth factor (EGF) and examined potential relationships between normalization of the EGF and restoration of fertility in repeat breeder cows. In Experiment 1, endometrial tissues were obtained by biopsy on Days 3, 7 and 14 of the estrous cycle from 99 fertile dairy cows and normal ranges of uterine tissue EGF concentrations were determined. Then, eight fertile cows were examined for endometrial EGF concentrations on Days 3, 7 and 14 during the three consecutive estrous cycles. All eight cows had a normal EGF profile (EGF concentrations were within the normal ranges of all 3 days) in all three estrous cycles and endometrial EGF concentrations were similar among the three estrous cycles. In Experiment 2, 61 repeat breeder cows were examined EGF profile and 43 (70.5%) cows had altered EGF profiles compared with control profiles. A typical alteration was characterized by decreased concentrations on Days 3 and 14 and accounted for 86.0% of all alterations. When repeat breeder cows with altered EGF profiles (n = 17) were left untreated, abnormality persisted in 14 (82.4%) cows at the second examination and only 3 animals became pregnant within the next two estrous cycles. Among 15 cows showing a typical alteration at the first examination, 11 (73.3%) cows had the same alteration until the third examination performed after two infertile inseminations following the second examination. When repeat breeder cows with altered EGF profiles (n = 26) were given one of four therapeutic treatments, cows in which the EGF profile normalized after treatment had a greater pregnancy rate than those with altered profiles (11/14 animals versus 3/12 animals pregnant; P < 0.05). In conclusion, suppressed endometrial EGF concentrations on Days 3 and 14 may be common alterations and persist between estrous cycles in repeat breeder cows. Potential relationship between normalization of the endometrial EGF profile and restoration of fertility was observed. Additional study to confirm results of the treatment is, however, necessary because the present study used a limited number of animals. Nevertheless, current data suggest that normalization of the EGF profile is one of the prerequisite factors to restore fertility.