Alteration of the Endometrial EGF Profile as a Potential Mechanism Connecting the Alterations in the Ovarian Steroid Hormone Profile to Embryonic Loss in Repeat Breeders and High-producing Cows

Poor reproductive efficiency is a worldwide problem that has affected the dairy industryduring the last several decades. In an attempt to explain the changes in reproductivephysiology caused by high milk production, a model of elevated steroid metabolism inlactating dairy cows has been proposed. A slow increase in levels and low peak levels ofestradiol (E₂) and progesterone (P₄) characterize endocrine changesin high producing cows. Similar changes have been reported in the repeat breeder cows. Theabnormal changes in E₂ and P₄ concentrations of these cows may causean improper uterine environment due to disturbed expression of growth factors andcytokines in the endometrium. This review focuses on the alteration in epidermal growthfactor (EGF) profile in the endometrium during the estrous cycle. The normal cow has twopeaks of EGF concentrations on days 2–4 and 13–14. Low concentrations of EGF on these daysdistinguished both high-producing and repeat breeder cows from normal cows. Alteration ofthe EGF profile could be found in 70 and 40% of the repeat breeder and high-producingcows, respectively. Treatment with a high dose of estradiol benzoate and an intravaginalprogesterone-releasing device restored the normal EGF profile in about 70% of the affectedcows. The cows having a normal EGF profile after treatment showed a higher pregnancy ratethan the cows with the altered profile. Further studies to understand the etiology of thealteration in the EGF profile are needed to develop another treatment option andpreventive management for this problem.