Evaluating the influence of heritable, metabolic, and production variables on the postpartum estrus expression of Holstein cows in a voluntary milking system

Abstract

Objective

This observational study aimed to explore metabolic markers, nonesterified fatty acids (NEFA), glucose, insulin, and insulin resistance, alongside heritable fertility marker anti-Müllerian hormone (AMH), and their influence on postpartum estrus expression in a voluntary milking system (VMS).

Materials and Methods

Holstein cows (n = 95) were enrolled at 14 ± 3 DIM with blood samples taken weekly. All samples were analyzed for metabolic profiles of NEFA, glucose, and insulin until 49 ± 3 DIM. Insulin resistance was estimated at each time point using the Revised Quantitative Insulin Sensitivity Check Index (RQUICKI). Visits to the VMS and milk production data were collected on day of sampling and averaged with data from the preceding day and following day. Cows were fitted with DeLaval AM2 collars and monitored from calving until 100 DIM using DelPro Farm Manager. Both (++) (activity 5 SD above normal activity levels) and (+++) (activity 6 SD above normal activity levels) reproductive attentions in DelPro were used to identify an estrus event, with estrus intensity recorded. Cows were grouped by time to resumption of estrus expression, with the normal group (NG) having an estrus event on or before 45 DIM and the delayed group (DG) resuming beyond 45 DIM. Data were analyzed using the CORR and MIXED procedure of SAS.

Results and Discussion

Greater milk yield corresponded with increased VMS visits (r = 0.39). Blood glucose concentrations were greater for NG cows on d 35 and 42. Serum NEFA concentrations decreased in all animals over time. Insulin increased over time in all cows but did not differ between NG and DG cows. The RQUICKI did not change over time for either NG or DG cows. Estrus intensity was not different in NG (191% ± 6.6%) versus DG cows (179.1% ± 5.97%), and AMH was not different between NG (223.4 ± 28.62 pg/mL) and DG cows (217.6 ± 25.22 pg/mL).

Implications and Applications

Milk production and its association with glucose and VMS visits are key drivers for postpartum estrus expression of cows in a VMS.