Utilization of nitrogen-15 from wheat by growing poultry and laying hens

Nitrogen-15 offered to broiler chickens and laying hens has been tested. The test animals were given wheat (atom % 15N-excess 20-25%) or 15N-lysine in balanced rations. The results showed that different feedstuffs are transported selectively through the gastro-intestinal tract. Therefore the atom % 15N-excess is higher in the contents of the crop, the proventriculus and the gizzard in comparison with the feed. Some hours after feeding the atom % 15N-excess in the contents of the small intestine is lower than in other parts of the intestinal tract (3 to 12 hours after feeding). As to atom % 15N, there is a significant correlation between the contents of the small intestine and the gut wall (r=0.99). As the amount of nitrogen in the contents of the small intestine does not change between 3 and 12 hours after feeding, the obvious dilution of 15N does not allow conclusions to be made regarding the endogenic secretion. In the steady state, 24% of the 15N of wheat lysine, 12% of the 15N of wheat histidine and 9% of arginine were excreted in the faeces. Four days after the last feed intake of labelled wheat or lysine we found more 15N in the carcass than in the total sum of eggs. Four days after the last feeding the albumen showed a higher labelling rate than urine. The 15N of wheat was differently incorporated into thoracic, leg and heart muscles. We found a different half-life time for the individual muscle protein types in the following order: heart, leg, thoracic. Within the eight-day period no changes were observed in the level of labelling in the thoracic muscle. (author)