Factors associated with early cyclicity in postpartum dairy cows

摘要

The objective of this study was to evaluate factors associated with resumption of ovarian cyclicity within 21 days in milk (DIM) in dairy cows. Cows (n = 768) from 2 herds in north Florida had their ovaries scanned at 17 ± 3, 21 ± 3, and 24 ± 3 DIM. Cows that had a corpus luteum ≥20 mm at 17 ± 3 or at 21 ± 3 DIM or that had a corpus luteum ＜20 mm in 2 consecutive examinations were determined to be cyclic by 21 ± 3 DIM. The following information was collected for up to 14 DIM: calving season, parity, calving problems, metabolic problems, metritis, mastitis, digestive problems, lameness, body weight loss, dry period length, and average daily milk yield. Body condition was scored at 17 ± 3 DIM. Multivariable mixed logistic regression analysis was performed using the GLIMMIX procedure of SAS. Variables with P ≤ 0.2 were considered in each model. Herd was included as a random variable. Three models were constructed: model 1 included all cows, model 2 included only cows from dairy 1 that had daily body weights available, and model 3 included only multipa-rous cows with a previous dry period length recorded. In model 1, variables associated with greater cyclicity by 21 ± 3 DIM were calving in the summer and fall rather than in the winter or spring, being multiparous rather than primiparous, and not having metabolic or digestive problems. In model 2, variables associated with greater cyclicity by 21 ± 3 DIM were calving in the summer and fall, not having metritis or digestive problems and not losing ＞28 kg of BW within 14 DIM. In model 3, variables associated with greater cyclicity by 21 ± 3 DIM were absence of metabolic problems and dry period ≤76 d. In summary, cyclicity by 21 ± 3 DIM was negatively associated with calving in winter or spring, primiparity, metritis, metabolic or digestive problems, loss of ＞28 kg of body weight, and a dry period ＞76 d. Strategies preventing extended dry period length and loss of BW, together with reductions in the incidence of metritis as well as metabolic and digestive problems should improve early cyclicity postpartum.