Nieuwenhuizen L, Dekker A W, te Brake J H, Maatje K, Rossing W
Tijdschr Diergeneeskd. 1979 Apr 1;104(7):312-9.
The temperatures of twenty cows were recorded rectally from five days prior to the expected date of oestrus till after ovulation at 2.30, 7 and 12 a.m. and at 5 and 10 p.m. The cows were also examined for oestrus behaviour at these times. When the cows had stood to be mounted for the first time at one of the hours of observation, the ovaries were examined by palpation at the subsequent times to detect ovulation. The total number of cows in heat, in which marked oestrous behaviour was observed, was forty-one. In addition, there were eight cases of silent oestrus, i.e. though the animals did ovulate and usually showed an increase in temperature, they did not stand to be mounted. Variance analysis showed that de 'cow effect', the time of day, the stage of oestrus, the oestrus number and the interaction of the stage of oestrus and the time of day had a significant effect on the body temperature. In 86 per cent of the cases of oestrus (including those of 'silent oestrus'), there was a significant increase in body temperature. This proportion was much smaller, namely 55 per cent, when observations were made about milking time only (7 a.m. and 5 p.m.). The mean difference between the highest temperature during oestrus and the average reference temperature was 0.62 degrees C +/- 0.38 degrees C. Daily monitoring of the temperature was also found to be useful in checking the state of health of the dairy herd.
