Metabolic indicators as predictors of reproductive disorders in holstein dairy cows: a field-based study

The aim of this study was to investigate associations between pre- and post-partum serum metabolites and reproductive and health outcomes and finding critical thresholds of serum metabolites to predict future reproductive outcomes in Holstein dairy cows from two commercial dairy farms in Tehran province, Iran. In total, 366 Holstein dairy cows (207 from Farm A and 159 from Farm B) were enrolled into the study. The cows were managed under a TMR feeding system and monitored through calving and early lactation, with blood samples collected at five time points for analysis of β-hydroxybutyrate (BHBA), non-esterified fatty acids (NEFA), glucose, calcium, magnesium, Aspartate transaminase, total protein, albumin, cholesterol, urea and phosphorus. Logistic regression identified significant metabolic predictors of dystocia, early culling (≤ 60 Days in milk), cystic ovarian disease, anestrus, endometritis, first service conception rate, embryonic death, abortion, and pregnancy outcomes. Elevated pre-partum NEFA and calcium increased dystocia risk, whereas low pre- and post-partum calcium, magnesium, glucose, and protein were associated with higher odds of early culling and reproductive disorders. NEFA, BHBA, and phosphorus were consistently linked to ovarian dysfunction, while albumin and glucose influenced endometritis and fertility. Metabolic status associated with periparturient health events, including retained placenta and metritis, together would modify reproductive success. These findings indicated that both energy balance and mineral/protein status during the transition period were critical determinants of health and fertility in Holstein cows. Monitoring serum metabolites may enable early identification of at-risk animals and support targeted nutritional and management interventions to improve reproductive performance.