The use of infrared skin temperature measurements for monitoring heat stress and animal welfare

Abstract

The present investigation was carried out to use body surface temperature as an alternate to measurement of rectal temperature for monitoring heat stress and animal welfare. Four non-pregnant dry crossbred cattle were exposed together to three treatment temperatures (25, 35 and 40°C) with a relative humidity of 40-50%, housed in the climatic chamber to simulate different environmental heat stress conditions. The animals were exposed to each temperature for 5 hours/day from 10:00 to 15:00 hours for 21 days. The respiratory rate (RR), rectal temperature (RT) and pulse rate (PR) were recorded at 09:30 hours (before exposure) and 15:00 hours (after exposure) every day. The surface temperatures (ST) of the fore leg, head, neck, lumbar, thigh and hind leg were recorded before and after exposure at five days interval (day 1, 6, 11, 16 and 21) with the help of infra-red digital thermometer. The RT, RR and PR increased significantly (P<0.01) after exposure at 35 and 40°C; showed that animals were stressed. The ST was similar at neck, lumbar and thigh region both before and after exposure at 35 and 40°C. The ST at different anatomical sites was positively correlated (P<0.01) with exposure temperatures. Numerically, maximum correlation of exposure temperature was observed with forelimb (r=0.928) and hind limb ST (r=0.929). The maximum correlation of RT was observed with thigh (r=0.756, P<0.05) and minimum correlation was observed with neck ST (r=0.698, P<0.05). The results showed that the fore and hind limb ST measured by infrared thermometry may be used to measure environmental heat stress whereas thigh ST may be used as an alternative to RT to assess the increase in body temperature due to heat stress in cattle.