ASABE Technical Library - Abstract

Abstract. The US dairy industry, a $40 billion per year industry (2013), loses more than $1.5 billion in a typical year to the effects of heat stress on lactating dairy cattle. Core temperature is a reliable indicator of heat stress, but measuring core temperature may require restraint of the animal. Skin temperature measurements are fast and non-invasive, but skin temperature is typically a less reliable indicator of heat stress. Because the udder of a cow is highly vascularized and has a high blood flow rate, we tested whether udder skin temperature is useful as a heat stress indicator.

For this research, eight primiparous, mid-lactation Holstein cows producing 34.4 ± 3.7 kg/d of milk were housed in two identical climate-controlled rooms with tie stalls and exposed to moderate heat stress (THI 79.5 ± 1.2) for 8 h per day. Cows were given one week to adjust to the facility, then data was collected for five weeks on milk production, feed consumption, core temperature, respiration rate, udder skin temperature, and body surface temperature in three unshaved locations (neck, back and side). Cows were milked twice daily and fed ad libitum. Core temperature was measured twice each day before heat stress conditions and after 8 h of heat stress. Respiration rate, udder skin temperature, and body surface temperatures were measured before heat stress and every 2 h during heat stress. Four experimental cows were randomly assigned to be cooled with conductive cooling by circulating chilled water through modified DCC waterbeds, and these cows experienced less heat stress than control cows did. For the final week of the experiment, experimental and control cows were switched.

Correlations among daily milk production and feed consumption, core temperature at the end of heat stress, and the daily average under heat stress of respiration rate, udder skin temperature, and body surface temperature were analyzed in JMP. Correlation with milk production was strongest for core temperature (0.67), followed by feed consumption (0.58), udder skin temperature (0.53), respiration rate (0.38), and body surface temperature (0.23). Thus, udder skin temperature may be useful as a fast, non-invasive measurement of heat stress.