[Effect of bovine growth hormone on performance criteria of dairy cows during summer feeding with grass. 1. Feed intake and protein and energy supply].

The influence of long-term administration of bovine growth hormone (bGH) with prolonged release (Somidibove from Lilly Germany GmbH, section Elanco, 640 mg/28 d) in six consecutive injection periods on feed intake under summer feeding conditions with grass feeding ad libitum was investigated. After a pretreatment period of 22 days 30 dairy cows were divided into 15 blocks with two cows each in consideration of milk yield, days postpartum and number of calving. In each block the bGH-treated animal received the same concentrate supply as the corresponding control animal which was supplemented in order to requirement. In a 42 day posttreatment period without bGH-injection possible effects of bGH-treatment on feed intake (grass silage and maize silage) was investigated. The first injection was administrated 75 days postpartum, respectively. During all six injection periods feed intake corrected to the pretreatment period was increased by 0.63 kg DM/animal.d resulting from a higher grass intake in the bGH-treated dairy cows compared to the control group. This difference in feed intake raises from 0.40 kg DM/animal.d in the first injection period up to 0.84 kg DM/animal.d in injection period six and continued in the posttreatment period without bGH-injection (+0.89 kg DM/animal.d). The higher feed intake of grass in the injection periods by the bGH-treated dairy cows resulted in an increased energy intake sufficient on average for the production of 1.2 kg milk/animal.d. Possibilities and limits of a sufficient nutrient supply in bGH-treated dairy cows by an increasing intake of grass are discussed.