Mc Geough E J, O'Kiely P, Hart K J, Moloney A P, Boland T M, Kenny D A
Teagasc, Grange Beef Research Centre, Dunsany, Co. Meath, Ireland.
J Anim Sci. 2010 Aug;88(8):2703-16. doi: 10.2527/jas.2009-2750. Epub 2010 Apr 9.
This study aimed to quantify the methane emissions and feed intake, performance, carcass traits, digestibility, and rumen fermentation characteristics of finishing beef cattle offered diets based on whole-crop wheat (WCW) silages differing in grain content and to rank these relative to diets based on grass silage (GS) and ad libitum concentrates (ALC). In Exp. 1, a total of 90 continental crossbred steers [538 +/- 27.6 kg of BW (mean +/- SD)] were blocked by BW and assigned in a randomized complete block design to 1 of 6 treatments based on 4 WCW silages [grain-to-straw plus chaff ratios of 11:89 (WCW I), 21:79 (WCW II), 31:69 (WCW III), and 47:53 (WCW IV)], GS, and ALC. Increasing grain content in WCW silage resulted in a quadratic (P = 0.01) response in DMI, with a linear (P < 0.001) increase in carcass gain [CG; 577 (WCW I), 650 (WCW II), 765 (WCW III), and 757 g/d (WCW IV)]. The G:F also increased linearly (P < 0.001) in response to increasing the grain content of WCW silage. A quadratic (P < 0.01) response in daily methane output [295 (WCW I), 315 (WCW II), 322 (WCW III), and 273 g/d (WCW IV)], measured using the sulfur hexafluoride tracer technique, was observed in response to increasing the grain content of WCW; however, linear decreases were observed when expressed relative to DMI (P = 0.01) and CG (P < 0.001). Cattle offered GS exhibited carcass gains similar to those offered WCW silage diets and had greater methane emissions than cattle in any other treatment when expressed relative to DMI. Cattle offered ALC exhibited greater (P < 0.01) carcass gains and decreased (P < 0.001) methane emissions, irrespective of the unit of expression, compared with cattle in any of the silage-based treatments. In Exp. 2, rumen fermentation parameters were determined using 4 ruminally cannulated Rotbunde-Holstein steers (413 +/- 30.1 kg of BW) randomly allocated among WCW I, the average of WCW II and III (WCW II/III), WCW IV, and GS in a 4 x 4 Latin square design. Ruminal pH and total VFA concentration did not differ across dietary treatments. Molar proportion of acetic acid decreased (P = 0.01), with propionic acid tending to increase (P = 0.06) with increasing grain content. It was concluded that increasing the grain content of WCW silage reduced methane emissions relative to DMI and CG and improved animal performance. However, the relativity of GS to WCW in terms of methane emissions was dependent on the unit of expression used. Cattle offered ALC exhibited decreased methane emissions and greater performance than those offered any of the silage-based treatments.
本研究旨在量化给育肥牛饲喂基于全株小麦（WCW）青贮饲料且谷物含量不同的日粮时的甲烷排放量、采食量、生产性能、胴体性状、消化率和瘤胃发酵特性，并将其与基于青贮牧草（GS）和自由采食精料（ALC）的日粮进行比较排序。在试验1中，总共90头大陆杂交阉牛[体重538±27.6千克（均值±标准差）]按体重进行分组，并采用随机完全区组设计，分配至基于4种WCW青贮饲料[谷物与秸秆加谷壳比例分别为11:89（WCW I）、21:79（WCW II）、31:69（WCW III）和47:53（WCW IV）]、GS和ALC的6种处理中的1种。WCW青贮饲料中谷物含量增加导致干物质采食量呈二次曲线反应（P = 0.01），胴体增重呈线性增加（P < 0.001）[胴体日增重；577（WCW I）、650（WCW II）、765（WCW III）和757克/天（WCW IV）]。随着WCW青贮饲料谷物含量增加，料重比也呈线性增加（P < 0.001）。使用六氟化硫示踪技术测定的每日甲烷产量呈二次曲线反应（P < 0.01）[295（WCW I）、315（WCW II）、322（WCW III）和273克/天（WCW IV）]，随着WCW谷物含量增加而变化；然而，相对于干物质采食量（P = 0.01）和胴体增重（P < 0.001）时，呈线性下降。饲喂GS的牛胴体增重与饲喂WCW青贮饲料日粮的牛相似，相对于干物质采食量，其甲烷排放量比其他任何处理的牛都高。与任何基于青贮饲料的处理组相比，饲喂ALC的牛胴体增重更大（P < 0.01），甲烷排放量降低（P < 0.001），且不受表达单位的影响。在试验2中，使用4头安装了瘤胃瘘管的Rotbunde - Holstein阉牛（体重413±30.1千克），采用4×4拉丁方设计，随机分配至WCW I、WCW II和III的平均值（WCW II/III）、WCW IV和GS组，测定瘤胃发酵参数。不同日粮处理间瘤胃pH值和总挥发性脂肪酸浓度无差异。随着谷物含量增加，乙酸的摩尔比例下降（P = 0.01），丙酸有增加的趋势（P = 0.06）。研究得出结论，增加WCW青贮饲料的谷物含量相对于干物质采食量和胴体增重可降低甲烷排放量，并提高动物生产性能。然而，GS与WCW在甲烷排放方面的相关性取决于所使用的表达单位。与任何基于青贮饲料的处理组相比，饲喂ALC的牛甲烷排放量降低，生产性能更好。
