Tang Qingfeng, Shao Pengcheng, Wen Chongli, Bu Zeming, Qin Guangsheng, Huang Yali, Pan Yuhong, Li Zhipei, Wei Kelong, Li Shulu, Lan Bishi, Zhong Huapei, Zou Caixia
College of Animal Science and Technology, Guangxi University, Nanning, 530004, Guangxi, China.
Buffalo Research Institute, Chinese Academy of Agricultural Sciences, Nanning, 530001, Guangxi, China.
Trop Anim Health Prod. 2025 Jun 4;57(5):245. doi: 10.1007/s11250-025-04494-5.
The goals of ruminant protein nutrition are to provide sufficient rumen-degradable protein (RDP) for optimizing nitrogen utilization efficiency and achieve the desired level of animal productivity, all while minimizing dietary crude protein (CP) intake. The present study aimed to examine the effects of decreasing dietary protein by reducing RDP on the growth performance, energy, and nitrogen metabolism of dairy buffalo heifers. Three diets were formulated: high RDP (H-RDP, RDP = 80.36 g/kg, CP = 15.42%), medium RDP (M-RDP, RDP = 72.79 g/kg, CP = 14.03%), and low RDP (L-RDP, RDP = 66.48 g/kg, CP = 12.87%), yielding digestible crude protein (DCP) balances of 166.07, 114.89, and 66.59 g/d, respectively. The diets were fed to 36 heifers (259.19 ± 3.93 kg) divided into three groups (12 heifers per treatment) over a 51-day trial. The results showed that when dietary RDP decreased from 80.36 g/kg to 72.79 g/kg, the average daily gain (ADG) and dry matter intake (DMI) remained stable; however, a further decrease to 66.48 g/kg resulted in a 19.12% decrease in ADG and an 6.80% decrease in DMI (P < 0.05). The feed-to-gain (F/G) ratio increased linearly with decreasing dietary RDP (P < 0.01) and was significantly lower in the M-RDP and H-RDP groups than that in the L-RDP group (P < 0.05). The apparent digestibility of CP decreased linearly (P = 0.01) and was significantly higher (P < 0.05) in the H-RDP group than in the L-RDP group. There was a linear increase in fecal nitrogen efficiency (FN)/IN, which was significantly lower (P < 0.05) in the H-RDP group than in the L-RDP group. Reducing dietary RDP linearly decreased urinary nitrogen excretion (UN) (P < 0.01) without affecting the efficiency of the retained nitrogen (RN), intake nitrogen (IN), and energy profiles. Overall, this study revealed that reducing dietary RDP (from 80.36 to 72.79 g/kg) and CP (from 15.42% to 14.03%) effectively reduced UN excretion while maintaining dairy buffalo heifer performance. Collectively, these findings suggest an optimal dietary RDP range of 72.79-80.36 g/kg for 13- to 15-month-old dairy buffalo heifers.
反刍动物蛋白质营养的目标是提供足够的瘤胃可降解蛋白（RDP），以优化氮利用效率并达到期望的动物生产性能水平，同时尽量减少日粮粗蛋白（CP）摄入量。本研究旨在探讨通过降低RDP来减少日粮蛋白质对奶水牛小母牛生长性能、能量和氮代谢的影响。配制了三种日粮：高RDP日粮（H-RDP，RDP = 80.36 g/kg，CP = 15.42%）、中RDP日粮（M-RDP，RDP = 72.79 g/kg，CP = 14.03%）和低RDP日粮（L-RDP，RDP = 66.48 g/kg，CP = 12.87%），其可消化粗蛋白（DCP）平衡分别为166.07、114.89和66.59 g/d。在为期51天的试验中，将这些日粮饲喂给36头小母牛（259.19 ± 3.93 kg），分为三组（每组12头小母牛）。结果表明，当日粮RDP从80.36 g/kg降至72.79 g/kg时，平均日增重（ADG）和干物质摄入量（DMI）保持稳定；然而，进一步降至66.48 g/kg导致ADG下降19.12%，DMI下降6.80%（P < 0.05）。饲料转化率（F/G）随日粮RDP降低呈线性增加（P < 0.01），且M-RDP组和H-RDP组显著低于L-RDP组（P < 0.05）。CP的表观消化率呈线性下降（P = 0.01），H-RDP组显著高于L-RDP组（P < 0.05）。粪氮效率（FN）/摄入氮（IN）呈线性增加，H-RDP组显著低于L-RDP组（P < 0.05）。降低日粮RDP可使尿氮排泄（UN）呈线性下降（P < 0.01），而不影响氮保留效率（RN）、摄入氮（IN）和能量状况。总体而言，本研究表明，降低日粮RDP（从80.36降至72.79 g/kg）和CP（从15.42%降至14.03%）可有效减少UN排泄，同时维持奶水牛小母牛的生产性能。这些研究结果共同表明，13至15月龄奶水牛小母牛的最佳日粮RDP范围为72.79至80.36 g/kg。
