Reproductive Efficiency of Low-Fertility Dairy Cows Submitted to Presynch-Ovsynch or Double-Ovsynch Scheme for First Service.

Reproductive efficiency has a major impact on the profitability of dairy operations. Focusing on improving the reproductive performance of cows with expected reduced fertility is desired; however, further research is needed in this area. The objectives of this study were to identify a subpopulation of cows with suboptimal fertility and evaluate whether hormonal interventions would improve the reproductive efficiency of low-fertility cows. Cows in one herd were enrolled in the study at 50 days in milk (DIM) and classified as low or high fertility according to a proprietary Fertility Index. Weekly cohorts of cows were allocated to three treatments at 50 DIM: (1) high fertility and Presynch-Ovsynch (H-PO; n = 1036); (2) low fertility and Presynch-Ovsynch (L-PO; n = 665); (3) low fertility and Double-Ovsynch (L-DO; n = 645). The voluntary waiting period (VWP) was 65 and 50 DIM for first-lactation and second- and greater-lactation cows, respectively, regardless of the treatment group. For H-PO and L-PO treatments, Presynch-Ovsynch was initiated at 75 ± 3 DIM, and when cows were not inseminated early after detected estrus, timed artificial insemination (TAI) occurred at 113 ± 3 DIM. For cows assigned to the L-DO treatment, Double-Ovsynch was initiated at 53 ± 3 DIM, and when cows were not inseminated early after detected estrus, TAI occurred at 80 ± 3 DIM. All cows were eligible to be inseminated after the end of the VWP and during the entire presynchronization schemes. The Fertility Index successfully identified differences in pregnancy and culling outcomes regardless of the lactation number. Fewer cows (