This study investigated the effect of forage type (grass or red clover) and harvesting time (primary growth or regrowth) of silage on energy and N utilisation by sheep fed at maintenance level. Specifically, the assumption of constant loss of energy of digestible organic matter from energy losses in urine and CH4 applied in evaluation of silage metabolisable energy (ME) was investigated. Urinary excretion of high-energy phenolic compounds related to solubilisation of lignin was assumed to affect urinary energy (UE) losses from sheep fed highly digestible grass silage (GS). A total of 25 primary growth and regrowth silages of timothy (Phleum pratense) and meadow fescue (Festuca pratensis) grass mixtures and red clover (Trifolium pratense) samples collected in digestibility trials with sheep, including faecal and urine samples, were used for energy and N determinations. Urinary concentration of monophenolic compounds and CH4 emissions in vitro were also analysed. Daily faecal N output, CH4 yield (MJ/kg DM intake), proportion of CH4 energy in digestible energy (DE) and proportion of UE in DE were greater (P ≤ 0.03) in sheep fed red clover silage (RCS) than GS. Furthermore, less (P = 0.01) energy was lost as UE of DE in sheep fed primary growth GS compared with the other treatments. The relationship between UE and silage N intake or urinary N output for both silage types (i.e. grass v. red clover) was strong, but the fit of the regressions was better for GS than RCS. The CH4/DE ratio decreased (P < 0.05) and the UE/DE ratio increased (P < 0.05) with increasing organic matter digestibility in RCS. These relationships were not significant (P < 0.05) for the GS diets. The regression coefficient was higher (P < 0.05) for GS than RCS when regressing ME concentration on digestible organic matter. The results of this study imply that ME/DE ratio is not constant across first-cut GS of different maturities. The ME production response may be smaller from highly digestible first-cut GS but could not be clearly related to urinary excretion of monophenols derived from solubilisation of lignin. Furthermore, energy lost in urine was not clearly defined for RCS and was much more predictable for GS from silage N concentration.

中文翻译：

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以维持水平饲喂绵羊的草和红三叶草青贮饲料的可代谢能量。

本研究调查了饲草水平（草料或红三叶草）和青贮饲料的收获时间（主要生长或再生）对维持水平饲喂的绵羊的能量和氮利用的影响。具体而言，研究了将尿液和CH4的能量损失中恒定的可消化有机物能量损失用于青贮饲料可代谢能量（ME）的假设。与木质素溶解有关的高能酚类化合物的尿排泄被认为会影响饲喂高消化率草料青贮饲料（GS）的绵羊的尿能（UE）损失。在绵羊的消化率试验中收集了总共25种提摩太（Phleum pratense）和草甸羊茅（Festuca pratensis）草混合物和红三叶草（Trifolium pratense）青贮和再生长的青贮饲料，包括粪便和尿液样品，用于能量和氮测定。还分析了单酚类化合物的尿液浓度和体外CH4排放。饲喂红三叶草青贮饲料（RCS）的绵羊的每日粪便氮产量，CH4产量（MJ / kg DM摄入量），CH4能量在可消化能量（DE）中的比例和UE在DE中的比例（GS）大于GS（P≤0.03）。此外，与其他处理相比，在饲喂初生GS的绵羊中，DE的UE损失的能量更少（P = 0.01）。两种青贮类型（即草对红三叶草）的UE和青贮氮摄入量或尿氮输出之间的关系很强，但GS的回归拟合比RCS更好。随着RCS中有机物消化率的提高，CH4 / DE比值降低（P <0.05），UE / DE比值提高（P <0.05）。这些关系不显着（P <0。05）对于GS饮食。当对可消化有机物的ME浓度进行回归时，GS的回归系数高于RCS（P <0.05）。这项研究的结果表明，不同期限的首批GS的ME / DE比率不是恒定的。易消化的一级馏分GS对ME的产生反应可能较小，但与木质素增溶衍生的单酚的尿排泄没有明显关系。此外，RCS尚无尿中能量损失的明确定义，而青贮N浓度对GS的可预测性要高得多。易消化的一级馏分GS对ME的产生反应可能较小，但与木质素增溶衍生的单酚的尿排泄没有明显关系。此外，RCS尚无尿中能量损失的明确定义，而青贮N浓度对GS的可预测性要高得多。易消化的一级馏分GS对ME的产生反应可能较小，但与木质素增溶衍生的单酚的尿排泄没有明显关系。此外，RCS尚无尿中能量损失的明确定义，而青贮N浓度对GS的可预测性要高得多。