Lactation curve-derived traits associated with conception outcomes in high-yielding dairy cows

Abstract

Abstract

High-yielding dairy cows experience substantial metabolic stress from early lactation, potentially impairing reproductive performance; however, lactation curve characteristics have not been comprehensively evaluated within a single analytical framework as predictors of conception outcomes at first artificial insemination (AI). This study analyzed 270 clinically healthy multiparous Holstein cows managed under a standardized reproductive program on a commercial Lithuanian farm. Peak milk yield, days to peak, and absolute milk yield decline from peak to artificial insemination were derived from DairyPlan C21 records, and pregnancy was diagnosed by transrectal ultrasonography. Associations with conception outcomes at first AI were assessed using multivariable logistic regression and chi-square tests. After adjustment for milk yield at AI, days to peak, and lactation number, peak milk yield was negatively associated in Model A (milk at AI model) with conception outcomes at first AI (OR = 0.88, 95% CI 0.82–0.95, P = 0.001), although this association was not evident in unadjusted analysis (OR = 0.95, P = 0.342). Each additional day to peak was associated with approximately 2.2% lower odds of conception (OR = 0.978, 95% CI 0.961–0.994, P < 0.01). Post-peak decline had the strongest effect, with each 1-kg increase associated with a 12.6% decrease in the odds of conception (OR = 0.87, 95% CI 0.81–0.94, P < 0.001) and conception rates decreasing across decline categories. These findings suggest that lactation curve traits, particularly post-peak decline (ΔMilk), represent the strongest variable associated with conception outcomes at first AI in high-yielding cows and may support exploratory decision-making regarding optimal artificial insemination timing using routinely collected milk data, pending validation in independent multi-herd studies.