The effect of low temperature on thermoregulation and energy metabolism in dairy cows

Six dairy crossbred cows (Czech Pied cattle with Holstein cattle) on their first lactation (initial daily milk yield was 16 l.cow(-1).day(-1)), were housed in the air-conditioned stable of the Research Institute of Animal Production in Prague. During nine week period the air temperature was successively decreased from +15 to -7 degrees C and again increased to +15 degrees C, with each week hiring a different temperature level. Three times a day the air temperature and the air humidity were noted. Data on oxygen consumption, pulmonary ventilation, breath frequency and heat production were obtained by mask method on the ergospirometer apparatus OXYCON-4 together with rectal temperature always after week adaptation of animals to a new air temperature level. A significant scale of non-linear correlation with the air temperature and a slight scale of linear one were found at oxygen consumption, heat production and breath frequency (I-(y,I-x) = 0.613-0.619, r((y,x)) = 0.109-0.148). These functions confirmed the existence of an adaptation zone to low temperatures between +10 degrees C and 0 degrees C. We deduce from the test data that chemical thermoregulation in dairy cows asserts only a little at low temperatures. The breath frequency accomplished high scale of non-linear correlation with the air temperature (I-(y,I-x) = 0.705) and also high scale of linear one (r((y,x)) = 0.656). The lowest rate of the breath frequency was observed at air temperatures below 0 degrees C, this also had a significant effect on the rectal temperature. After complex test data evaluation it can be enunciated that the followed dairy cattle was very well adaptable to thermal alteration of the environment.