Effects of osteopontin treatment alone and in combination with hormonal therapy on endometrial epidermal growth factor concentration and fertility at the first insemination after calving in dairy cows.

Delayed recovery of cyclic changes in epidermal growth factor (EGF) concentration in the endometrium is related to low conception rates at the first insemination following parturition. An intravaginal infusion of osteopontin (OPN) normalizes EGF profile and improves fertility in repeat-breeder (RB) cows. Therefore, the present study determined whether this treatment can restore normal EGF profile in postpartum cows and improve fertility. First, the effects of recombinant OPN (rOPN) and OPN peptide were examined. In cows with abnormal EGF profile, treatment with both rOPN and OPN peptides increased the normalization rate of EGF profile (78.3 % and 53.1 %, respectively) and conception rates (47.8 % and 61.2 %, respectively), with the rates being higher than those of the control group (25.0 % and 20.0 %, respectively). Second, the effects of combined OPN and hormonal therapy, an established treatment for this abnormality in RB cows, were investigated. Cows were treated with OPN peptide (320 nmol or 1600 nmol) alone and in combination with hormonal therapy. The combined treatment significantly increased EGF normalization and conception rates than the peptide alone (40.5 % vs. 21.9 % and 35.1 % vs. 19.0 %, respectively). The combined treatment achieved the highest conception rate among all groups, including those that received 1600 nmol OPN peptide with or without hormonal therapy. These results indicated that although OPN peptide alone improves fertility, combining it with hormonal therapy could be a better option in cows at the first insemination following parturition.