DEPOSITION OF ENERGY AND NUTRIENTS AND UTILIZATION OF ENERGY FOR GROWTH IN FATTENING CATTLE (GERMAN SIMMENTAL)

Bulls (n = 54), heifers (n = 45) and steers (n = 45) were fed either on high energy-level feed (maize silage ad libitum and 1.8 kg concentrate) or on low energy-level feed (restricted maize silage and 1.0 kg concentrate). Bulls and steers with a live mass of 200, 350, 500, 575, and 650 kg and heifers with a mass of 200, 350, 425 and 500 kg were slaughtered and the total body of each animal was analysed. From the data of empty-body gain, fat, protein and energy deposition in the different fattening periods was calculated. The utilization of energy for growth and maintenance was estimated by regression analysis. In bulls under intensive feeding conditions, the daily fat deposition decreased from 230 g to 170 g and for heifers from 299 g to 190 g. Steers showed an increasing fat deposition from 240 g per day to 290 g per day. On the low energy-level feed, the fat deposition increased from 83 g to 202 g in bulls and from 147 g to 262 g in heifers. Steers deposited an average of 180 g fat per day. Protein deposition decreased with increasing live mass from 246 g to 175 g in bulls, from 167 g to 78 g in heifers and from 183 g to 110 g in steers, whereas under a restrictive feeding system, bulls reached a protein deposition of between 182 g and 148 g/day. In heifers, protein deposition decreased from 128 g to 79 g and in steers from 138 g to 98 g per day. On high energy-level feed, the daily energy deposition of the bulls decreased with increasing live mass from 14.5 MJ to 10.7 MJ and from 15.5 MJ to 9.2 MJ for heifers, whereas steers showed an average energy deposition of 13.4 MJ. The daily water deposition also decreased with rising live mass. In the first regression analysis, a utilization of energy for fat deposition of 84% and for protein deposition of 47% was estimated. The requirement for maintenance amounted to 640 kJ/kg LM0,75. In a second regression analysis, a mean utilization of energy for growth of 45% and a mean energy requirement for maintenance of 535 kJ/kg LM0,75 were estimated.