DefinePK

Abstract

This study investigated factors influencing the number of services per conception (NSC) in dairy cows, focusing on age at first calving (AFC), cow’s age, parity, and days in milk (DIM) at first insemination. Data from 1014 lactating Holstein cows in a commercial farm in Denmark was collected. The effects of the studied factors on NSC were analyzed using the Kruskal-Wallis test with pairwise comparisons. The average NSC was 2.2±1.1. No significant effect of AFC on NSC at first AI was detected. However, significant associations between NSC and cow’s age (P=0.005), parity (P=0.001), and DIM (P<0.05) were found. NSC in cows at the age of <3 years (2.2±1.2), and 3-4 years (2.1±1.2) was smaller than that in cows at the age of >5 years (2.6±1.2). Cows in parity 1 exhibited a lower NSC compared to those in parities 2, 3, 4, and ?5 (2.0±1.1 vs 2.3±1.3, 2.3±1.3, 2.2±1.3, and 2.4±1.2, respectively). NSC levels in cows at ?81 DIM were higher than those at 51-80 DIM (P<0.01). These findings highlight the necessity of incorporating cow’s age, parity, and DIM into assessments of reproductive performance in dairy herds, with the potential for maximizing lifetime profit by reducing the optimal AFC to as early as 21 months.