Comparison of physical and behavioral traits between dairy cows with low and high somatic cell count.

The objective of this study was to examine associations of locomotion score, hygiene, body condition score (BCS), lying behavior, and milk production with dairy cow somatic cell count (SCC; low or high). Cows from 14 commercial free-stall dairy herds in Ontario, Canada were enrolled in a cross-sectional study. Each farm was visited for a total of 3 observation periods (at 5-wk intervals) on 2 occasions per period (7 d apart) until 3 Dairy Herd Improvement (DHI) milk tests had been completed. Upon immediate receiving of the results of each DHI test, lactating Holstein cows were selected according to SCC. Cows that ranked in the top 10% for SCC in each herd (≥200,000 cells/mL; n = 370) were first selected and paired based on parity and DIM to cows within the same herd with low SCC (≤100,000 cells/mL; n = 382). Lying behavior was recorded for selected cows for 6 d after each milk test sampling, using data loggers. On the visit where data loggers were attached, cows were scored for gait (1 = sound to 5 = lame) and hygiene of udder, lower legs, and upper legs/flank (1 = clean to 4 = dirty). On the visit where data loggers were removed 7 d later, BCS (1 = thin to 5 = fat) and hygiene were scored. Cows were then classified into each of the scoring categories for hygiene (clean: ≤ 2, dirty: ≥3), BCS (high: ≥4, normal: 3-3.5, low: ≤2.5), and gait (sound: ≤2, lame: ≥ 3). As compared to normal BCS cows, low BCS cows were associated with high SCC (OR = 1.57, 95% CI = 1.00-2.47). Cows with high SCC were associated with producing 2.2 ± 0.72 kg/d less milk than those with low SCC. As compared to normal BCS cows, low BCS cows were associated with reduced lying time (-27.2 ± 12.5 min/d), decreased lower leg hygiene (OR = 2.64, 95% CI = 1.08-6.46), and increased milk production (+2.9 ± 0.88 kg/d). These results suggest that low BCS may be a mediating factor among lying behavior, hygiene, and production level with high SCC.