The present study aimed to evaluate the effects of various rumen undegradable to rumen degradable protein ratios (RUP:RDP) on the performance, rumen fermentation pattern, urinary purine derivatives, and carcass characteristics in growing lambs when received a high dietary wheat straw level (420 g/kg, DM basis). Lambs (average initial live weight = 27.2 ± 2.4 kg) were individual housed (n = 18, 6 animals/treatment) to evaluate the effects of treatments. The RUP:RDP ratios tested were obtained through replacing extruded soybean meal (ESBM; RUP = 64 %, based on total CP) instead of conventional soybean meal (CSBM; RUP = 26 %, based on total CP) in proportion of 0, 50, and 100 % in order to obtain ratios of (1) low RUP:RDP ratio as LR diet (25:75); (2) moderate RUP:RDP ratio as MR diet (30:70) (3) high RUP:RDP ratio as HR diet (35:65). The study lasted 10 weeks. Dry matter intake did not differ among experimental treatments (P = 0.80), while average daily gain (ADG) and final BW were linearly improved (P < 0.05) with increased RUP:RDP ratio. Accordingly, the lowest feed efficiency observed in LR lambs and it was reduced linearly when RUP:RDP ratio was increased (P = 0.01). Although the amount of nitrogen intake was constant across experimental treatments (P = 0.69); however, the nitrogen to gain conversion ratio was increased as RUP:RDP being increased (P = 0.02). Digestibility of organic matter (P = 0.02) and crude protein (P = 0.03) as well as ruminal concentration of acetate (P = 0.05), urinary concentration of allantoin (P = 0.01), and blood glucose and insulin concentrations (P = 0.01) were linearly increased when lambs received diets contained high RUP:RDP ratio. In contrast, ruminal propionate concentration (P = 0.02) and urinary nitrogen concentration (P = 0.02) were reduced as RUP:RDP being increased. The dressing percentage was increased (P = 0.02) but mesenteric fat content (P = 0.03) and back-fat thickness (P = 0.01) were reduced when diets with higher RUP:RDP ratio being fed to lambs. In summary, high dietary RUP:RDP level is recommendable when growing lambs received wheat straw based-diet due to improvement in nutrient digestibility, nitrogen efficiency, and preventing high fat accretion within animal body.

本研究旨在评估高膳食小麦秸秆（420）下各种不可降解瘤胃对瘤胃可降解蛋白质比例（RUP：RDP）对生长羔羊的性能，瘤胃发酵模式，尿嘌呤衍生物和car体特性的影响g / kg，以DM为基础）。单独饲养羔羊（平均初始活重= 27.2±2.4千克）（n = 18，每只治疗6只动物）以评估治疗效果。通过以0、50的比例代替传统豆粕（CSBM； RUP = 26％，基于总CP）来代替膨化大豆粉（ESBM； RUP = 64％，基于总CP）来获得测试的RUP：RDP比率以及100％，以获得（1）低RUP：RDP比作为LR日粮（25:75）；（2）中度RUP：RDP比例作为MR饮食（30:70）（3）高中RUP：RDP比例作为HR饮食（35:65）。该研究持续了10周。实验处理之间干物质摄入量没有差异（P = 0.80），而平均日增重（ADG）和最终BW随着RUP：RDP比的增加而线性提高（P <0.05）。因此，在LR羔羊中观察到的最低饲料效率，并且当RUP：RDP比增加时线性降低（P = 0.01）。尽管在整个实验处理中氮的摄入量是恒定的（P = 0.69）；但是，随着RUP：RDP的增加，氮与氮的转化率也增加了（P = 0.02）。有机物（P = 0.02）和粗蛋​​白（P = 0.03）的消化率以及瘤胃中乙酸的瘤胃浓度（P = 0.05），尿尿囊素的尿酸浓度（P = 0.01）。），并且当羔羊接受高RUP：RDP比例饮食时，血糖和胰岛素浓度（P = 0.01）呈线性增加。相反，随着RUP：RDP的增加，瘤胃丙酸浓度（P = 0.02）和尿液氮浓度（P = 0.02）降低。敷料百分比增加（P = 0.02），但肠系膜脂肪含量（P = 0.03）和后脂肪厚度（P = 0.01）当将高RUP：RDP比的日粮饲喂羔羊时，可减少）。总而言之，当生长中的羔羊接受小麦秸秆为基础的饮食时，建议高饮食中的RUP：RDP水平，因为它改善了营养物质的消化率，氮效率并防止了动物体内高脂肪的积累。