以低质饲草为食的肉牛副产物饲料原料的瘤胃原位降解特性
In situ ruminal degradation characteristics of by-product feedstuffs for beef cattle consuming low-quality forage.
作者信息
Winterholler S J, Lalman D L, Dye T K, McMurphy C P, Richards C J
机构信息
Department of Animal Science, Oklahoma State University, Stillwater, OK 74078, USA.
出版信息
J Anim Sci. 2009 Sep;87(9):2996-3002. doi: 10.2527/jas.2008-1603. Epub 2009 Jun 19.
Eight ruminally cannulated steers (BW = 753 +/- 48 kg) were used to evaluate in situ N, NDF, and DM degradation characteristics of by-product feeds and their application for beef cows consuming low-quality forage. Experimental feedstuffs included (DM basis) 1) extruded-expelled cottonseed meal (ECSM; 33% CP and 55% NDF), 2) extruded-expelled cottonseed meal with linters (ECSML; 25% CP and 41% NDF), 3) dried distillers grains with solubles (DGS; 33% CP and 36% NDF), 4) solvent-extracted cottonseed meal (CSM; 43% CP and 29% NDF), and 5) a blend of 76% wheat middlings with 18% CSM (WMCSM; 23% CP and 40% NDF). Steers were fed chopped prairie hay (4.8% CP, 69% NDF; DM basis) ad libitum and received 0.38 kg/100 kg of BW of WMCSM daily. In situ degradation kinetics of N, NDF, and DM components included the following fractions: A (immediately soluble), B (potentially degradable), and C (undegradable). Calculated rumen degradable protein (RDP) for ECSM was the greatest among all feedstuffs (83.8%; P < 0.01), which was composed of a large A fraction of N (41%). Similar RDP values were observed for DGS and ECSML (50.7 and 50.9%, respectively, P = 0.93). The B fraction N for ECSML was large (88.9%); however, most of this was unavailable for ruminal degradation. The amount of RDP in CSM and WMCSM was similar (78.2 and 73.5%, respectively; P = 0.12) though the A fraction of N was greater for WMCSM compared with CSM (P < 0.01). Degradability of NDF was greatest (P < 0.01) for DGS (67.4%) and was similar (P = 0.48) for WMCSM and CSM (54.5 and 57.0%, respectively). The least degradability of NDF was calculated for ECSM (29.3%; P < 0.01), attributed to greater lignin content (13.3%, DM). Degradability of DM was greatest (P < 0.01) for CSM and WMCSM (63.7 and 59.4%, respectively) and least (P < 0.01) for ECSM (36.5%) and ECSML (40.6%). Ruminal N degradation characteristics of ECSM were similar to more traditional supplements containing CSM and WMCSM. The RDP for ECSML and DGS N was less compared with other feedstuffs, indicating these feeds may need to be blended with other ingredients containing greater concentrations of degradable N, particularly in situations in which forage RDP is low.
选用八头装有瘤胃瘘管的阉牛（体重 = 753 ± 48千克）来评估副产品饲料的原位氮、中性洗涤纤维和干物质降解特性，以及它们在采食低质粗饲料的肉牛中的应用。试验饲料（以干物质计）包括：1）挤压脱溶棉籽粕（ECSM；粗蛋白含量33%，中性洗涤纤维含量55%），2）带棉短绒的挤压脱溶棉籽粕（ECSML；粗蛋白含量25%，中性洗涤纤维含量41%），3）干酒糟及其可溶物（DGS；粗蛋白含量33%，中性洗涤纤维含量36%），4）溶剂浸出棉籽粕（CSM；粗蛋白含量43%，中性洗涤纤维含量29%），5）由76%小麦麸和18% CSM组成的混合物（WMCSM；粗蛋白含量23%，中性洗涤纤维含量40%）。阉牛随意采食切碎的草原干草（粗蛋白含量4.8%，中性洗涤纤维含量69%；以干物质计），每天每100千克体重采食0.38千克WMCSM。氮、中性洗涤纤维和干物质成分的原位降解动力学包括以下几个部分：A（立即溶解部分）、B（潜在可降解部分）和C（不可降解部分）。在所有饲料中，ECSM的瘤胃可降解蛋白（RDP）计算值最高（83.8%；P < 0.01），其氮的A部分占比很大（41%）。DGS和ECSML的RDP值相近（分别为50.7%和50.9%，P = 0.93）。ECSML的B部分氮含量很大（88.9%）；然而，其中大部分无法在瘤胃中降解。CSM和WMCSM的RDP量相似（分别为78.2%和73.5%；P = 0.12），不过WMCSM的氮A部分比CSM更大（P < 0.01）。DGS的中性洗涤纤维降解率最高（P < 0.01）（67.4%），WMCSM和CSM的降解率相近（分别为54.5%和57.0%，P = 0.48）。ECSM的中性洗涤纤维降解率计算值最低（29.3%；P < 0.01），这归因于其木质素含量较高（13.3%，干物质）。CSM和WMCSM的干物质降解率最高（P < 0.01）（分别为63.7%和59.4%），ECSM（36.5%）和ECSML（40.6%）的干物质降解率最低（P < 0.01）。ECSM的瘤胃氮降解特性与含有CSM和WMCSM的更传统补充料相似。与其他饲料相比（P < 0.01），ECSML和DGS氮的RDP较低，这表明这些饲料可能需要与其他可降解氮浓度更高的成分混合，特别是在粗饲料RDP较低的情况下。
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