| Abstract: | The tryptophan contents of 20 samples of various feedstuffs, determined by using assay procedures which were proved to give quantitative results, were compared with those predicted from the relationships between nitrogen and tryptophan published by three laboratories. The ratio of predicted tryptophan to the observed tryptophan, expressed as percentage, ranged from 65% (pea) to 137% (fishmeal). These differences were shown to be related to a systematic underestimation of tryptophan regarding data from two laboratories associated with a variability of tryptophan content for a given nitrogen content and a given type of feedstuff. |
