Department of Animal Sciences, University of Missouri, Columbia 65211, USA.
J Anim Sci. 2012 Dec;90(13):4985-94. doi: 10.2527/jas.2011-4107. Epub 2012 Jul 24.
We hypothesized that microbial efficiency and output from fermentation in the rumen would be optimized when peptide supply was balanced with peptide requirement of ruminal microflora. This study was conducted to measure response of varying rumen degradable peptide (RDPep) supply on ruminal fermentation characteristics and steer growth. A continuous culture experiment was conducted with diets formulated to achieve a predicted RDPep balance (RDPep supplied above RDPep required) of -0.30 to 1.45% CP with rumen degradable N (RDN) balance (RDN supplied above RDN required) above dietary ammonia-N requirement of microbes. Two additional treatments had RDPep balances of -0.30 and 0.78% CP with insufficient ammonia-N supply to meet microbial requirements. Single-flow fermenters (N = 24; n = 6) were inoculated with rumen fluid and maintained anaerobically at 39°C with a 0.06 h(-1) dilution rate. Inadequate RDN decreased OM digestion and microbial N flow, and increased rumen undegradable N (P < 0.01). Microbial efficiency decreased in RDN-deficient diets and was greatest when RDPep balance did not excessively exceed microbial requirement of RDPep predicted (P < 0.01). A growth study was conducted with 49 yearling, crossbred, Angus steers (initial BW 370 ± 34 kg). Animals were assigned to 1 of 4 treatment groups by BW and further divided into 3 pens with 4 steers per pen to achieve similar initial pen weights. Treatments consisted of 4 isonitrogenous diets balanced for RDN but varying in predicted RDPep balance (0.55%, -0.02%, -0.25%, and -0.65% CP). Animals were maintained on treatment for 70 d with individual BW taken on d 0, 1, 21, 42, 70, and 71. Final BW decreased linearly with decreasing RDPep (P = 0.05). Average daily gain and G:F displayed a quadratic effect with greater ADG and G:F at greater and lesser RDPep levels (P = 0.02). We concluded that balancing RDPep supply to predicted requirement improved fermentation efficiency and microbial output, which in turn improved animal performance.
我们假设，当肽供应与瘤胃微生物的肽需求平衡时，微生物效率和发酵产物将得到优化。本研究旨在测量不同瘤胃可降解肽（RDPep）供应对瘤胃发酵特性和育肥牛生长的反应。进行了一项连续培养实验，用配方饲料实现预测的 RDPep 平衡（RDPep 供应高于 RDPep 需要），-0.30 至 1.45% CP，瘤胃可降解氮（RDN）平衡（RDN 供应高于微生物需要的氨氮）。另外两个处理的 RDPep 平衡分别为-0.30 和 0.78% CP，氨氮供应不足，无法满足微生物的需求。单流发酵器（N = 24；n = 6）用瘤胃液接种，在 39°C 下保持厌氧状态，稀释率为 0.06 h（-1）。RDN 不足降低了有机物消化和微生物氮流量，并增加了瘤胃未降解氮（P < 0.01）。在 RDN 缺乏的日粮中，微生物效率下降，当 RDPep 平衡不过度超过预测的微生物对 RDPep 的需求时，微生物效率下降最大（P < 0.01）。对 49 头育肥牛（初始 BW 370 ± 34 kg）进行了生长研究。动物按 BW 分为 1 组，进一步分为 3 个栏，每个栏 4 头，使初始栏重相似。处理包括 4 种等氮日粮，平衡 RDN，但预测的 RDPep 平衡不同（0.55%、-0.02%、-0.25%和-0.65% CP）。动物在处理上维持 70 天，每天单独测量 BW，分别在第 0、1、21、42、70 和 71 天。随着 RDPep 的减少，终重呈线性下降（P = 0.05）。平均日增重和 G:F 呈二次效应，在更高和更低的 RDPep 水平下，ADG 和 G:F 更高（P = 0.02）。我们得出结论，平衡 RDPep 供应与预测需求提高了发酵效率和微生物产量，进而提高了动物生产性能。
