Dintzis F R, Cavins J F, Graf E, Stahly T
Northern Regional Res. Center, U.S. Department of Agriculture, Peoria, IL 61604.
J Anim Sci. 1988 Jan;66(1):5-11. doi: 10.2527/jas1988.6615.
Nitrogen-to-protein conversion factors were calculated for diets and fecal samples from three animal species fed low- or high-fiber diets. The conversion factors based on protein contents determined by amino acid analyses were calculated from total N (Kjeldahl analyses) and recovered amino acid plus NH3-N (amino acid analyses). Conversion factors based on protein contents determined by a fluorescamine assay for amino acids were also calculated from total Kjeldahl-N. The conversion factors based on Kjeldahl-N averaged 5.3 +/- .7 for the diets and 4.0 +/- .5 for the feces in the six animal and diet comparisons when calculated from anhydrous amino acid formula weights. The greatest deviations from the traditional 6.25 conversion factor occurred in the fecal samples of ruminant animals fed a corn-alfalfa meal diet at a maintenance level of intake. In contrast, conversion factors based on amino acid plus NH3-N were quite stable. These factors averaged 5.7 +/- .1 for feeds and 5.5 +/- .1 for feces when calculated from anhydrous amino acid residue weights.
计算了三种动物在饲喂低纤维或高纤维日粮时，日粮和粪便样本中的氮-蛋白质转化因子。基于氨基酸分析测定的蛋白质含量的转化因子，是根据总氮（凯氏定氮法分析）以及回收的氨基酸加氨态氮（氨基酸分析）计算得出的。基于氨基酸荧光胺测定法测定的蛋白质含量的转化因子，也是根据凯氏定氮总氮量计算得出的。在六组动物和日粮比较中，当根据无水氨基酸分子式量计算时，基于凯氏定氮氮的转化因子，日粮平均为5.3±0.7，粪便平均为4.0±0.5。与传统的6.25转化因子偏差最大的情况，出现在维持摄入水平下饲喂玉米-苜蓿粉日粮的反刍动物粪便样本中。相比之下，基于氨基酸加氨态氮的转化因子相当稳定。当根据无水氨基酸残基量计算时，这些因子饲料平均为5.7±0.1，粪便平均为5.5±0.1。
