The effect of low temperatures on the meat performance and behaviour of beef bulls

The trials with dairy cows (1987 to 1988) were followed up by investigations of beef bulls. In an experimental shed there were two groups, each comprising eight beef bulls and their live weight ranged from 258 to 367 kg (during the experiment). In the control group (K 4) temperatures in the shed were from 13.8 to 14.6 degrees C, in the experimental group (P) the temperature in period I (six weeks) made -4.3 degrees C and in period II (five weeks) -0.8 degree C. The optimum temperature in view of liveweight gains was recorded in period II, when the weight gain of the P group was 1 187.9 g per head/day; this was by 10.5 per cent more than in the K group. At the low temperatures (period I) the weight gain was 986 g, i. e. 95.2 per cent in comparison with the K group. In period I the bulk feed intake was higher by 1.0 per cent and in period II it was higher by only 0.5 per cent if compared with the K group. In conversion per 1 kg liveweight gain the intake of dry matter in period I was higher by 7.2 per cent, the intake of digestible crude protein by 6.5 per cent (=absolutely 613.6 g) and that of starch units by 7.2 per cent (= absolutely 3.95 starch units). In period II the intake of dry matter decreased to 91.1 per cent, the intake of digestible crude protein to 90.7 per cent (=absolutely 519 g) and that of starch units to 91.6 per cent (=absolutely 3.95 starch units). The consumption of drinking water was lower by 0.5 to 19.5 per cent. An analysis using the model of multivariate linear regression demonstrated that the increasing relative air humidity (within the given interval) exerted a small influence on decreases in liveweight gains. The intake of bulk feeds was influenced negatively by the relative air humidity at low temperatures; at higher temperatures the intake of bulk feeds was increasing with the higher values of relative air humidity. The increasing relative air humidity had also positive effects on water consumption. An evaluation of the behaviour of animals showed that the time of rumination was longer by 5.2 per cent in comparison with the control group. This finding is in close relation with meat performance.