EFFECT OF LOW-TEMPERATURES ON MILK-YIELD, BODY-WEIGHT AND FEED-INTAKEOF DAIRY-COWS

Thirty Holstein cows were matched by stage of lactation and milk yield by pairs. They were then randomly assigned to housing treatment group s. The trial group was kept in an open free-stall barn and the control group ina warm enclosed tie-stall barn. Milk yield was measured twice daily by computer, feed consumption was recorded individually. An ave rage of minimum temperatures in the open barn (Tab. I) was lowest duri ng the eighth (-19.4 degrees C) and during seventh out of twelve weeks of the experiment, the averages below -10 degrees C were recorded. In the warm barn the average of minimum temperatures was lowest during t he eighth week (0.9 degrees C) and so was the lowest temperature (-3.5 degrees C) there. The highest average relative humidity in the, open barn (Tab. II) was recorded during the sixth week (92.8%), in the warm barn during the tenth and eleventh week (85.1% and 85.9%). Wind veloc ity and direction and solar radiation during the particular weeks are shown in Tab. III. In all weeks the milk production was higher in the trial group (Tab. IV). The average production during the whole period of the experiment (32.7 kg and 30.96, kg) was significantly different. Cows from the control group housed in a warm barn showed higher body weight during the whole experiment compared to the trial group. The di fferences, however, were not significant. In both groups the body weig ht increased from the second to the twelfth week (Tab. V), During the whole experiment feed intake was higher in dairy cows kept in the open barn (Tab. VI). Highly significant differences were recorded during 1 st, 2nd, 5th, 10th, 11th and 12th week and the greatest difference dur ing the whole period of observation was on the tenth week when the fir st group consumed 35.3 kg of feed in an average and the second group 2 3.5 kg. The average daily feed consumption in the animals from the ope n barn during the whole experiment was 35.79 kg, which is 123.1% of th e intake of the dairy cows kept in the warm barn. The intake of dry ma tter, crude protein and net energy is shown in Tab. VII. During the wh ole experiment, the feed consumption per 1 kg of milk in dairy cows fr om the open barn was higher by 16.8% compared with the control group f rom the warm barn (Tab. VIII). Tab. IX shows linear dependences of mil k yield on feed intake. As expected, the relations are positive, in th e trial group,during 10 weeks above the level r > 0.4. Tab. X shows a regression analysis between the indices of age and body weight. Relati ons between the body weight and the age and between the body weight an d the number of lactation were positive in both groups of cows during the experiment.