The purpose of this study was to explore the effects of nitrogen-free diets on cecal microflora and endogenous amino acid basal losses of broilers aged 14 and 35 days. A total of 308 Male Ross broiler chickens, aged 10 and 31 days, respectively, were chosen and randomly assigned into two dietary treatments, in which one was fed a conventional diet and the other was fed a nitrogen-free diet for 4 days. Every treatment contained five replicates with 12 chickens on day 10 and 6 chickens on day 31 per replicate. The results showed that endogenous basal losses of most amino acids determined by excreta-based assay were significantly higher than those determined by ileum digesta-based assay in broilers aged 14 and 35 days (P<0.05 or P<0.01). Compared with the conventional diet, there were some changes of DGGE predominant bands of cecal microflora 16S rDNA V3 region in broilers fed the nitrogen-free diet aged 14 and 35 days, the 72% and 39% of total gray value of predominant bands changed respectively for broilers fed the nitrogen-free diet aged 14 and 35 days. On day 14, there was no significant difference in cecal digesta weight and ammoniacal nitrogen concentration in broilers between nitrogen-free diet group and conventional diet group (P >0. 05) , but the concentrations of butyric acid (P< 0.01) , isobutyric acid (P< 0.05) and valeric acid (P < 0. 05) in cecum digesta of broilers were significantly decreased and propionic acid concentration was significantly increased (P <0. 01) by the nitrogen-free diet compared with the conventional diet. On day 35, compared with conventional diet group, cecal digesta weight of broilers in the nitrogen-free diet group was significantly increased, and the concentrations of ammoniacal nitrogen, acetic acid, isobutyric acid, valeric acid and isovaleric acid were significantly decreased (P<0.01). In conclusion, endogenous basal losses of most amino acids measured by excreta-based assay are higher than those measured by ileal digesta-based assay when broilers are fed the nitrogen-free diet. Some predominant species of cecal microflora should change after broilers are fed the nitrogen-free diet for 4 days. [ Chinese Journal of Animal Nutrition, 2012, 24 (10) : 1878-1887 ]%本试验旨在研究无氮饲粮对14日龄和35日龄肉鸡盲肠微生物菌群结构及内源氨基酸基础损失量的影响.分别选用10日龄和31日龄罗斯(Ross) 308雄性肉鸡,随机分为2个组:常规饲粮组和无氮饲粮组,每组5个重复,其中10日龄时每个重复12只鸡,31日龄时每个重复6只鸡,试验期均为4d.结果表明:肉鸡14日龄和35日龄时,收粪法所得大多数氨基酸内源基础损失量均显著或极显著高于回肠食糜法(P＜0.05或P＜0.01).相对常规饲粮,无氮饲粮改变了14日龄和35日龄肉鸡盲肠微生物16S rDNA V3高变区变性梯度凝胶电泳图谱的优势条带,其中14日龄和35日龄发生变化的优势条带灰度值占其整个优势条带总灰度值的比例分别为72％、39％.与常规饲粮相比,无氮饲粮对14日龄肉鸡盲肠食糜重、氨态氮浓度没有显著影响(P＞0.05),但极显著降低了盲肠食糜中丁酸浓度(P＜0.01),显著降低了异丁酸和戊酸浓度(P＜0.05),极显著增加了丙酸浓度(P＜0.01).无氮饲粮组35日龄肉鸡盲肠食糜重极显著高于常规饲粮组(P＜0.01),盲肠食糜氨态氮、乙酸、异丁酸、戊酸、异戊酸浓度则极显著降低(P＜0.01).综上所述,采用无氮饲粮测定内源氨基酸基础损失量时,收粪法所得大多数氨基酸内源基础损失量显著高于回肠食糜法.饲喂无氮饲粮4d后,肉鸡盲肠食糜原有微生物优势菌群发生改变.
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