The utilization of crude proteins from 15N-labeled straw by broiler hen breeds

In an experiment with 10 colostomized broiler breeding hens the digestibility of wheat straw meal labelled with 15N and the incorporation of heavy nitrogen into individual body fractions were studied. The straw meal contained a 15N excess (15N') of 14.88 atom-%. Before the experiment part of the straw meal was treated with gamma-rays (2.0 MGy). 5 animals each received in addition to the basic ration 30 g untreated (group I) and irradiated 15N labelled straw meal (group II). The apparent 15N' digestibility amounted for untreated straw meal to 49% and for irradiated straw meal to 46% (p less than 0.05). The labelling of uric acid amounted to 0.25 atom-% 15N', urine with 0.30 atom-% 15N' was more highly labelled (p less than 0.05). On an average of both groups the same labelling of 0.18 atom-% could be detected in the follicles and the liver, whereas 0.17 were ascertained in the blood plasma and 0.16 atom-% 15N' in the oviduct. 18% of the digested 15N' were incorporated in the muscles. There were only insignificant differences between the two groups with regard to the incorporation of 15N'. In conclusion one can say that the apparent digestibility of straw protein is 47.5% and that the utilization of the absorbed N is about the same as that of wheat protein.