Possibility of depressive effects of dietary purine compounds on feed intake in young chickens

本研究旨在阐明嘌呤类化合物是否能降低鸡的采食量并阐明其作用机制，最终提高细菌、真菌和藻类等单细胞蛋白作为家禽配合日粮蛋白源的利用率。结果表明：1）肌肉注射腺嘌呤可降低鸡的采食量，而静脉注射和颈动脉注射则无此作用; 2）10%和0.96%的RNA日粮均能降低生长期鸡的采食量和生长速度; 3）日粮中33%的RNA能被作物中的酸度和温度自动降解为腺嘌呤，回肠对RNA的消化率为93%。4）饲喂10%RNA日粮时，鸡肝门血中游离腺嘌呤含量仅为饲喂0.96%腺嘌呤日粮时的35%;这表明，从肠中游离腺嘌呤的角度来看，10%RNA饮食对应于0.34%由此可见，日粮RNA并不是通过RNA消化增加游离腺嘌呤而降低采食量的，而是通过其它因素如PRPP的消耗而降低采食量的。因此，烟酰胺的消耗可能与饲料RNA引起的摄食量下降有关，因为PRPP对鸡体内烟酰胺的合成至关重要。

This study was carried out to elucidate whether purine compounds can reduce feed intake by chickens and to clarify its mechanisms, and finally to increase the utilization of single-cell protein such as bacteria, fungi and algae as protein sources for poultry formula diet. The results are summarized as follows:1) Adenine reduced feed intake in chickens when intramuscularly administered, but not when intravenous and intracarotid injection were done.2) Both 10% RNA diet and 0.96% diet reduced feed intake and growth in growing chickens as reported in young chicks.3) Dietary RNA of 33% was automatically degraded to adenine by acidity and temperature in the crop, and the digestibility of dietary RNA at the ileum was 93%. The most free adenine from the degradation was found in the crop, and decreased with descending the intestine.4) The free adenine in the hepatic portal blood when 10% RNA diet was fed to chickens accounted for only 35% of that when 0.96% adenine diet was fed, suggesting that from the point of free adenine in the intestine 10% RNA diet corresponds to 0.34% adenine diet.It is concluded that dietary RNA does not reduce feed intake through the increased free adenine from RNA digestion but through other factor such as PRPP depletion in chicken body. Therefore, depletion of nicotin amide is possibly involved in depression of feed intake caused by dietary RNA because PRPP is essential for nicotin amide synthesis in the chicken.