Published in Scientific Papers. Series D. Animal Science, Vol. LXVIII, Issue 2
Written by Hristo HRISTOV, Toncho PENEV, Kalin DIMITROV
The report aimed to present our study of the relationship between the temperature-humidity index (THI) and the surface temperature of the eye, and the thigh of Holstein-Friesian cows raised on a farm in southeastern Bulgaria, using infrared thermography (IRT). Measurements were conducted twice a month, May, June and July, twice a day at 10:00 AM and 5:00 PM, respectively. The correlation coefficient between the maximum eye temperatures and the temperature-humidity index was 0.7. The correlation coefficient between the surface temperature of the skin of the cows in the thigh area and the temperature-humidity index was 0.92. With an increase in the temperature-humidity index values, the rate of increase in the maximum eye temperature values was the highest (Slope=0.136). The rate of increase of minimum thigh surface temperatures with rising THI values is around 0.30 (Slope=0.297). The increase in the values of the temperature-humidity index leads to an increase in the temperature of the eyes and the surface temperature of the thigh in dairy cows, which is a result of an increase in the heat load on their body. The temperature of the thigh increases faster than the temperature of the eyes when the THI increases because the thigh is an area with massive muscles, which, in addition to its other role, is probably used for increased heat loss under conditions of heat stress.
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