Environmental temperature effects on milk production and daily activity of dairy cows with respect to different breeds

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Bazzell, Ashton
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University Honors College, Middle Tennessee State University
Heat stress is an animal’s response to an increase in thermal environment that causes the animal to inadequately dissipate heat out of the body. This stress occurs at temperatures over 77 °F, when cows are unable to cool themselves down. This increase in heat stress causes a decrease in milk production because more energy is needed to cool down, so there is less energy focused on producing milk. Temperature and relative humidity data, as well as daily milk yield, daily activity, and conductivity, were measured for three 6-week periods during different seasons to determine the effects of environmental temperature on milk production and activity levels. Cows produced more milk during the spring period (p < 0.0001) and had a higher conductivity in the summer (p < 0.0001). Jerseys were more active through each period than Holsteins (p < 0.0001) and mild heat stress occurred in the summer with an average THI index of 76.3. The optimum temperature range for Jerseys occurred during the spring period (18°C average temperature), while the optimum temperature for Holsteins occurred during the winter period (8.5°C average temperature).