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减少鸡的采食量，并阐明其作用机制，最终提高细菌、真菌、藻类等单细胞蛋白作为家禽配方日粮蛋白质来源的利用率。结果表明：1)肌肉注射时，腺嘌呤降低了雏鸡的采食量，但静脉注射和颈动脉注射时不会减少采食量。2)10%的RNA日粮和0.96%的日粮都降低了雏鸡的采食量和生长速度。3)饲料中33%的RNA被作物中的酸度和温度自动降解为腺嘌呤，饲料RNA在回肠的消化率为93%。4)饲喂10%RNA日粮时，肝门静脉血中游离腺嘌呤的含量仅为0.96%时的35%，表明从肠道游离腺嘌呤的角度来看，10%RNA日粮相当于0.34%的腺嘌呤日粮。因此，日粮RNA不是通过增加RNA消化产生的游离腺嘌呤，而是通过其他因素，如鸡体内的PRPP耗竭。因此，由于PRPP对鸡体内烟酰胺胺的合成是必需的，因此，日粮RNA导致的采食量下降可能与烟酰胺素的耗竭有关。

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.