[Protein and amino acid metabolism in the digestive tract of growing young bulls. 4. Apparent digestibility of NH3-free raw protein reaching the duodenum and critical evaluation of apparently digestible raw protein].

The experimental determination of the apparent digestibility (AD) of the NH3-free crude protein at the duodenum (NH3 fr. CPD) showed a value of 65.7% at a standard error of +/- 3.6% for the section of the digestive tract between proximal duodenum and end of rectum. This standard error can only be insignificantly diminished due to the existing relation between AD of NH3 fr. CPD in dependence on the CP concentration in the ration (y = 56.4 + 0.598 x +/- 3.17; r = 0.501xx) so that this relation has no practical significance. The criticism of AD CP is correct from a point of view of digestion physiology. There is only agreement between AD PC and AD NH3 fr. CPD in a CP concentration range between 12.5 and 14.0% CP in the DM, which, however, applies to a large range of the production sphere in the rearing of young bulls. It excludes, however, the low live weight range with high live weight gains.