RESPONSES OF DAIRY-COWS TO AN ADMINISTRATION OF BOVINE SOMATOTROPIN IN THE DIFFERENT PHASES OF CALVING INTERVAL

The effects of bovine somatotropin administration in different phases of calving interval (a fortnight before parturition - group A, on the day of parturition - group B, 35 days after parturition - group C, no administration - group K) on milk production and feed conversion during 16 weeks were investigated in 50 dairy cows - crossbreds of the Bohemian Pied and Black Pied Lowland breeds divided into four groups. The significantly (P 0.05) highest average milk performance (26.9 kg FCM) and at the same time the lowest energy balance (-22.1 IU NEL) were recorded in dairy cows of group A; this was due to the considerably higher milk performance [by 6.7 kg FCM) after parturition. This group was followed by dairy cows of group B with the average performance of 25.0 kg FCM and energy balance -16.1 NEL. There were no great differences in the performance and energy balance in dairy cows of group C (24.3 kg FCM; -13.1 IU NEL) and K (24.2 kg FCM; -12.7 IU NEL). After the fadeaway of somatotropin effects, the performance of dairy cows in groups A and. B decreased to the level of milk yield in dairy cows of group K.