Associations of hygiene and lying behavior with the risk of elevated somatic cell count and lameness

Abstract Text:

The objective of this study was to identify how cow-level factors and housing management affect the risk of elevated SCC (eSCC) and lameness in lactating dairy cows. Cows from 6 commercial free-stall dairy herds in Ontario, Canada were enrolled in a longitudinal study. Ten Holstein cows/herd were randomly selected based on DIM (<120d), absence of mastitis treatment in the last 3mo, and SCC (<100,000cells/mL). Data on SCC were collected through DHI testing (~5-wk intervals). The study began within 7d after a DHI-milk test, continued until 3 tests were completed (~105d), for a total of 3-observation periods/cow. Elevated SCC was used to indicate subclinical mastitis. An incident of eSCC was defined as a cow having a SCC >200,000cells/mL at the end of a period when SCC was <100,000cells/mL at the beginning of that period. Lying behavior was recorded for 6d after each milk sampling using data loggers. On d1 of each recording period a trained observer scored cows for lameness (5-point numerical rating scale, NRS≥3=lame). Hygiene scoring (4-point scale), also done by a trained observer, occurred on each visit. Cows were categorized as clean=≤2 or dirty=≥3. Stall cleanliness was assessed with a 1-m² metal grid, containing 88 squares, centered between stall partitions of every 10^th stall, and then counting the squares containing visible urine and/or fecal matter. Data were analyzed using multivariable logistic regression models. Cows averaged (mean±SD) 627±107.7min/d lying, 9±2.8 lying bouts/d, and 72±19.9min/bout. Over the study period, 13 eSCC were detected, resulting in an incidence rate of 0.73 eSCC/cow-year at risk. The risk of experiencing an eSCC increased 1.4x (P<0.01) with every 20,000cells/mL SCC increment at the beginning of the study. Mean proportion of soiled squares/stall was 27%. Each SD (18.8%) increment in proportion of dirty squares/stall was associated with lameness (NRS≥3) (OR=1.5; P=0.05) and increased the odds of having a dirty udder (DU) (OR=2.4; P=0.02). Each SD (108min/d) increment in lying time/d increased the risk of having dirty upper legs and flank (DULF) (OR=2.1; P<0.01), and tended to increase the risk of having a DU (OR=1.44; P<0.08). For each 9.6% increase above mean (100%) cow/stall stocking density, the risk of having DULF increased by 1.7x (P=0.03). These results indicate that lower stocking density and management practices that improved stall hygiene and should be encouraged to reduce the risk of poor hygiene and clinical lameness in dairy cows housed in free-stall barns.

Keywords:

subclinical mastitis, lameness, cleanliness