[The effect of bovine growth hormone on the production criteria of dairy cows during summer feeding with grass. 2. Milk yield, milk composition and live weight].

The influence of long-term administration of bovine growth hormone (bGH) with prolonged release (Somidibove from Lilly Germany GmbH, section Elanco) on milk yields, milk composition and live weights in six following injection periods of 28 days each was investigated. 30 dairy cows were divided into 15 blocks of two, each pair in consideration of milk yield in a preperiod, days postpartum and number of calving. One animal in each block received the bGH treatment (640 mg bGH/28 days). Concentrate feeding of the bGH-treated cows acted according to the control animal in each block. The forage intake from grass was ad libitum. During all six injection periods the bGH-treated cows had a higher milk yield of 1.3 kg/day (P < or = 0.13). Milk fat content was unchanged, milk protein content was in relation to the changes from preperiod significantly higher in the bGH-treated group. Each injection resulted in a curvilinear response curve of daily milk yield, milk fat and milk protein content. Milk lactose content was not affected by the bGH-treatment.