INFLUENCE OF RESPIRATION RATE AND RECTAL TEMPERATURE IN HOLSTEIN COWS TO MILK PRODUCTION DURING HEAT STRESS

The aim of this paper is to examine the relationship between rectal temperature and respiration rate and the production of milk during exposure to heat stress. The results show that increased values of temperature humidity index (THI) cause increases of respiration rate, so that for every unit of THI over 64, respiration rate increases by 0.6. The correlation coefficient between the rate
of respiration and THI was 0.55 (p <0.05). Rectal temperature in cows increases by 0.09 ° C for each unit of THI over 64. The correlation between the THI and the mean rectal temperature was highly significant and amounts to 0.92 (p <0.01). The results show a very high negative correlation between the respiration and the production of milk (-0.82, p <0.01) i.e. rectal temperature and milk production (-0.92, p <0.01). For each unit of respiration (breath / min) over 45, the amount of milk decreases by about 0.3 L, while for every degree over for the rectal temperature, the milk production decreases by about 3.5 L (0.35l/0.1 °C). The respiration rate and THI showed a slight linear dependence, probably because during the trial there was mild to moderate thermal load of cows.