[Protein utilization in calves during different periods of liquid feed fattening]

2 groups of male calves (Braunvieh) each comprising 5 animals with liveweights, at the day of slaughtering, of 58 kg, 99 kg and 155 kg were used in a trial that was carried out to obtain data on the utilization of dry matter, crude protein, crude fat and ash in the bipartite feeding of calves. The nutrient content of the animals was determined by total body analysis. The following values for nutrient retention were obtained in comparative slaughtering trials by using differentiation techniques. No significant differences between the two fattening periods were observed concerning the utilization of total dry matter in the milk substitutes. About 24% of the dietary dry matter were retained. The mean value for the utilization of dietary fat during the whole period of fattening was found to be about 55% provided, the fat was not used as energy source to meet maintenance requirements. 49% of the milk proteins were utilized for both retention and maintenance in the first period of fattening and 55% during the second period. Differences between the two periods showed no consistent trend. In view of the fact that for all animals used in the trial digestibility was taken to be 95% the utilization coefficients for the digested crude protein were higher by about 3% compared with the figures for crude protein. After subtraction of maintenance needs it was found that, on an average, 63% of the residual amount of digested protein available over the whole fattening period were retained in the body. 55% to 57% of the retained protein were deposited in those parts of the body of the animals that are used for human nutrition. It is for this reason that in the first half of the fattening period only 29.8% of the ingested dietary proteins were retained in the edible cuts of the animal body, as compared with 30.4% during the second half of the fattening period.