Abstract #503

# 503
Association between social ranking and health of transition dairy cows.
Karen M. Lobeck-Luchterhand*1, Paula R. B. Silva1, Ricardo C. Chebel1, Marcia I. Endres1, 1University of Minnesota, St. Paul, MN.

The objective of this study was to determine whether social ranking was associated with health of transition dairy cows. A total of 953 Jersey cows were used in the analysis. Cows were examined on DIM 1, 4, 7, 10, and 13 for the diagnosis of retained fetal membranes (RP) and metritis. Metritis was defined as cows with watery, pink or brown, and fetid uterine discharge; acute metritis included cows that had a fever (>39.5°C). Cows were classified with subclinical ketosis when BHBA concentration was ≥1200 µmol/L. Cows were observed once daily for displacement of abomasum (DA) and thrice daily for mastitis. Displacements from the feedbunk were measured continuously for 3 h after fresh feed delivery 4 d/wk during the 4 wk before calving for determination of social rank. A displacement index (DI) was calculated for each cow as the number of displacements as actor (cow initiated the displacement) divided by total displacements as actor or reactor (cow received the displacement). Displacement index was used on a continuous scale (method 1) and also categorized into social rankings (method 2); cows with a DI <0.4 were considered low-ranking, 0.4 to 0.6 were considered middle-ranking, and >0.6 were considered high-ranking. Additionally, the top and bottom 10th percentile for DI were selected to examine cows on the extreme ends of DI (method 3). Cows were categorized into bottom (DI <0.19), middle (0.19–0.71), and top 10th percentile (DI > 0.71). Proc Logistics in SAS was used to investigate the association between social ranking (defined by each of the 3 methods above) and health. Displacement index was associated with RP (AOR = 1.02, 95% CI 1.00–1.03), metritis (0.99, 0.97–1.00) and incidence of mastitis up to 60 DIM (0.99, 0.97–1.00). High-ranking cows were 2.0 times (1.08–3.70) more likely to have RP than low-ranking cows with no differences between low- and middle-ranking cows. The bottom 10th percentile DI cows were 4.7 times (1.6–13.4) more likely to have a case of metritis than the top 10th percentile ranking cows. A cow’s ability to displace another cow from the feedbunk during the prepartum period as a determinant of her social rank was not very consistent in predicting the odds of having a transition health disorder.

Key Words: social rank, transition cow, displacement index