Studies on energy and nitrogen metabolism in calves at different environmental temperatures

Energy and nitrogen metabolism were measured in black pied carves at 5, 15 and 25 degrees C environmental temperatures (ET). 3 experimental periods were carried out with 4 calves per group. At the beginning of the 3 periods the calves had mean body weights of 44, 81 and 122kg. The animals got milk replacers restrictively, the other feedstuffs as concentrates, hay and silage ad libitum. According to the parts of feedstuffs the chemical composition of the rations changed from period to period. For instance the content of crude fibre increased from 5 to 190g/kg DM. The energy digestibility of the rations amounted to 96% (Period 1), 79% (Period 2) and 68% (Period 3). In total no significant influence of ET on digestibiiity was found; only in the periods 2 and 3 digestibility was 2%-units higher at 25 degrees C. ET had influence on N-metabolism. The heat production (HP), measured in respiration chambers by indirect calorimetry was 29% higher at 5 degrees C and 14% higher at 15 degrees C in comparison to 25 degrees C in period 1. In period 2 HP was 10% higher at 5 degrees C compared to 15 and 25 degrees C. In period 3 no influence of ET was recorded.