THE EFFECT OF THERMAL ENVIRONMENT ON DAILY MILK YIELD OF DAIRY COWS

The primary objective of this research was to evaluate the impact of environmental air temperatures on the milk production of dairy cows. Therefore, the experiment was carried out at the height of summer (from 15th of June to 15th of September) in three small family dairy farms and one commercial dairy farm. In total, 51 dairy cows from the black-white breed were subjected to the study. The season of research was divided into three periods: the period before the hot season, the period of the hot season and the period after the hot season. In each period there were three test days selected that were used for recording the air temperature inside and outside the barns and cow's daily milk yield. Unvaried associations between the test day milk yield of cows and independent environmental and cow factors were done using the linear mixed model for repeated measurements. The statistical model showed that the farm management system and the hot season of the year had significant influence on daily milk yield per cow at the level of p<0.001. The test day per periods of the season when milk control was performed and the average test day environmental temperature showed statistically significant influence on daily milk yield per cow at level p<0.01. The present results revealed that environmental air temperatures contributes to considerable loss in the milk production of dairy cows.