Date of Award

12-2018

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

Gina Pighetti, Peter Krawczel

Committee Members

Agustin Rius

Abstract

Dairy cow health and welfare recommendations based on lying behavior and udder health are standardized in systems that rely on confined housing. However, factors may influence mastitis and behavior differently under organic pasture systems, due to changes in time budgets and treatment methods. Our objectives were to 1) determine the association of lying behaviors with cow-level factors, including milk yield, DIM, and parity when cows are managed under two organic management systems 2) identify probability of subclinical mastitis on organic farms in the southeastern region of the US and 3) characterize frequency and probability of mastitis-causing organisms by season, parity, and stage of lactation in this region. For objective 1, farms were categorized based on housing and feeding management. Lying behavior was seasonal and primiparous cows were more active than multiparous cows on all farms. Differences in behavior also were observed relative to milk yield on high input farms. Relative to objective 2 and 3, the probability for subclinical mastitis on organic farms was greatest in the summer, in older cows, and in early and late lactation. However, specific organisms found in milk from cows identified as recently having subclinical mastitis only differed in probability by parity. This indicates that specific pathogens may be driving the increased probability of subclinical mastitis in older cows. The association with season and stage of lactation may be more widespread and related to a decline in immune function due to other stressors present during summer and early lactation. Overall, a loss in milk production was associated with subclinical mastitis. Further work should identify 24-h time budgets and the chronicity of mastitis in organic herds, as well as the effect of cumulative stressors on udder health. Overall, our work establishes similarities between factors associated with behavior and mastitis on organic farms as has previously been established on conventional farms. However, our results indicate that the seasonal variation in lying behavior and mastitis may indicate a need for welfare recommendations specific to pasture-based cows.

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