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Housing and demographic effects on somatic cell score in southeast United States dairies
The objective of this study, as part of the Southeast Quality Milk Initiative, was to evaluate the effects of housing systems and farm demographics on SCS. From June 22, 2014 to June 21, 2015, dairy producers in KY (n = 96), TN (n = 83), VA (n = 96), and MS (n = 7) participated in an on-farm survey.
Each survey variable’s effect on SCS was evaluated using the GLM procedure in SAS with no covariates. Significant farm demographic variables were then included as co-variates in a GLM alongside herd size, state, and all two-way interactions. The same process occurred for significant housing variables with confinement type also included (total confinement, < 4 hours outside access, ≥ 4 hours outside access, or exclusively pasture). Backward stepwise elimination was used to eliminate non-significant interactions (P > 0.05).
In the housing model, state (P < 0.01) and confinement type (P < 0.04) were significantly associated with SCS. Herds in KY (4.33) and VA (4.43) had a lower SCS than MS (4.84) and TN (4.70; P < 0.02) herds. Total confinement herds had a lower SCS than herds with outside access (4.23, 4.67, 4.51, and 4.71 for total confinement, < 4 hours outside, ≥ 4 hours outside, and exclusively pastured herds, respectively; P < 0.03). Non-significant variables included: herd size, alley scraping frequency, fan availability, sprinkler availability, year of last housing renovation, and all interactions.
In the farm demographic model, state (P < 0.01), age (P < 0.01), and plans to be in business in 5 years (P = 0.02) were significantly associated with SCS. Producers ≥ 66 years old managed herds with higher SCS compared to all other age groups (4.43, 4.38, 4.56, 4.45, 4.58, and 5.06 for < 26, 26 to 35, 36 to 45, 46 to 55, 56 to 65, and ≥ 66 years old, respectively; P < 0.01). Producers responding that they were “almost certainly” going to be in business in 5 years had lower SCS than producers responding they were “very likely” to be in business in the same time frame (4.38 and 4.72, respectively; P < 0.01). Non-significant variables included: herd size, regularly scheduled veterinarian visits, producer education level, plans to be in business in 10 years, and all interactions.
These results suggest both housing and demographics are associated with SCS in the southeastern US.
Keywords: mastitis management SQMI