Ovarian protein hormones as biomarkers of fertility in dairy cows – Is it an acceptable model to predict infertility in dairy breeds?

Female dairy cattle are particularly prone to infertility/subfertility with pregnancy rates ranging as low as 27% to a high 40%. On average it takes more than one breeding/insemination event for dairy cattle to become pregnant. This results in a loss of the number of calves a female would have per year. There have been different methods that producers use to ensure a female ovulates in a timely fashion during artificial insemination (AI), including synchronization of estrus and ovulation by use of exogenous hormones. However, it is difficult to ascertain if a female is experiencing a fertile cycle at time of breeding. The purpose of this study was to determine if the ovarian protein hormones anti-Mullerian hormone (AMH) and inhibin A can be used as biomarkers for fertility of dairy breed cows. Blood was sampled from dairy breed mature cows and first-calf heifers housed at the Oregon State University Dairy before and during breeding by timed artificial insemination techniques near the time of insemination. Their serum was analyzed for AMH and inhibin A concentrations by Enzyme-Linked Immunosorbent Assays (ELISAs) previously validated in cattle (Ansh Labs) to determine if changes in these hormones correlated to pregnancy outcome. Samples were assigned to assay runs at random. Inter- and intra-assay coefficients of variation (CV) were within acceptable limits for ELISAs (AMH 17.4% and 2.8-2.7%; inhibin A 7.8% and 5.1-3.6%). While inhibin A assays had lower inter-assay CV, even with randomizing samples to two separate assay runs, significant differences were detected between samples run on different days (students t-test p=0.03). This might reflect a skew in pregnant females not detected in AMH assays (p > 0.9; n=45 samples, 27 non-pregnant, 18 pregnant), however, to avoid assay bias a Mixed Model function of SAS was used to analyze serum inhibin A results, using assay as a random variable. AMH levels were analyzed by one-way ANOVA (SAS). Levels of AMH within one week of breeding (pre-breeding sample