Reproductive parameters in dairy cattle exposed to high ambient temperatures

Abstract

Six Friesian cows in mid lactation were exposed on two temperature regimes: (i) 23.4°C RH 75% for 6 hours, 18.0°C RH 75% for the remaining 18 hours daily, for the duration of one oestrous cycle and (ii) 34.5°C RH 68% for 6 hours and 20.0°C and RH. 70% for the remaining 18 hours daily and for one oestrous cycle.

Net reductions in food and water intake and in milk production were recorded.

Rectal temperature and respiration increased significantly for all animals following daily exposure to the higher temperature.

The mean length of the oestrous cycle increased, one cow showed a shortening of cycle length.

Progesterone levels did not alter significantly at the higher temperature treatment.

Each cow had a characteristic pattern of progesterone production at each cycle.

The results are presented in tabular form and discussed briefly.