Characterization Of Dairy Cow Welfare Under Mild Acute Stressors: Heat Stress And Elevated Stocking Density

As with all living organisms, lactating dairy cows face numerous stressors; in commercial settings, these may include overstocking and environmental heat stress, during the summer months of the year. Overstocking is defined as limited access to resources related to milking, resting, feeding, or drinking. Overstocking reduces dairy cow welfare by preventing cows from meeting recommended resting times. Additionally, when dairy cows are overstocked, any additional stressor may have greater negative effects on dairy cow welfare than overstocking alone. Heat stress is an example of an unavoidable stressor that occurs when environmental temperatures increase above a set point, causing animals increase respiration rate and body temperature, which then leads to behavioral and immunological changes. Individually, both overstocking and heat stress affect a dairy cow’s welfare, however the effects of overstocking and heat stress on behavior is less known. The overarching hypothesis was that cows experiencing overstocking conditions when an automatic milking system was utilized, or concurrently with heat stress at the freestalls and feed bunk, will change their behavior and immune function. The objectives were three-fold: 1) determine the effects of varying stocking density on diurnal automatic milking system use and milk production variables; 2) determine the effects of overstocking, heat stress, and concurrent overstocking and heat stress on dairy cow behavior; and 3) determine the effects of overstocking, heat stress, and concurrent overstocking and heat stress on dairy cow immune function. We learned that as stocking density increased: 1) cows will use the automatic milking system at times when it is less occupied and 2) milk production variables plateaued when stocking density exceeded 64 cows, suggesting a baseline stocking density of 64 cows should be considered. We also learned that lactating cows experiencing overstocking while environmental heat stress conditions occurred, spent less time laying and more time standing in a resting space. Finally, we learned that cows under concurrent overstocking and moderate environmental heat stress had an increased immune response. Overstocking, with or without environmental heat stress conditions, will lead to changes in cows’ behavioral and immune response, in attempt to improve their welfare under stressors.

I have made the requested changes. Dr. Edwards is waiting for this to be approved before sending in the signed form. It should be in early afternoon.