Federal University of Minas Gerais, Department of Animal Science, Belo Horizonte, MG, Brazil.
Michigan State University, Department of Animal Science, East Lansing, MI, United States of America.
PLoS One. 2019 Jul 26;14(7):e0220247. doi: 10.1371/journal.pone.0220247. eCollection 2019.
Crossbreeding has been used to improve performance in beef cattle, however the effects of breed composition on methane (CH4) production, yield and intensity from cattle raised in tropical intensive and integrated systems remain unknown. To assess the impact of breed composition on performance and methane emissions, Nellore (NEL; yr 1: BW = 171.5 ± 19.4 kg; n = 10; yr 2: BW = 215.8 ± 32.3 kg, n = 25) and Angus x Nellore crossbred (AN; yr 1: BW = 214.2 ± 26.4 kg, n = 10; yr 2: BW = 242.5 ± 32.2 kg, n = 25) were compared. The animals grazed on integrated crop-livestock system in the growing phase (stocking rate 2452 kg BW/ha, herbage mass 4,884 kg dry matter (DM)/ha, forage allowance 5.9 kg DM/100kg BW) and then were finished in a feedlot. Steers (n = 8) from each breed composition were randomly selected in each phase to measure CH4 production using a sulfur hexafluoride (SF6) tracer technique and DM intake (DMI) using titanium dioxide. Compared with NEL, AN had both superior total gain and average daily gain (ADG) in the grazing period. The AN presented greater ADG in the feedlot with a shorter finishing period and resulted in greater carcass yield and carcass ADG. Methane production (kg/period) was lower in NEL (19% less) than AN in grazing (P<0.01), and no difference was observed in feedlot. The NEL had less CH4 intensity (CH4/BW) in grazing but greater CH4 per unit of ADG in the feedlot compared to AN. Breed composition did not influence the CH4 yield (CH4/DMI) in either phase, despite the difference in feedlot DMI (kg/day). In conclusion, crossbreeding may be an option to improve performance and reduce the CH4 per ADG in tropical climate conditions, resulting in lower methane emission per kg of meat produced.
杂交已被用于提高肉牛的性能，但在热带集约化和综合系统中饲养的牛的品种组成对甲烷（CH4）产生、产量和强度的影响尚不清楚。为了评估品种组成对性能和甲烷排放的影响，比较了内罗尔牛（NEL；第 1 年：BW=171.5±19.4kg；n=10；第 2 年：BW=215.8±32.3kg，n=25）和安格斯×内罗尔杂交牛（AN；第 1 年：BW=214.2±26.4kg，n=10；第 2 年：BW=242.5±32.2kg，n=25）。这些动物在生长阶段在综合作物-牲畜系统中放牧（放养率 2452kgBW/ha，牧草质量 4884kgDM/ha，饲料允许量 5.9kgDM/100kgBW），然后在育肥场育肥。在每个阶段，从每个品种组成中随机选择 8 头阉牛来测量 CH4 产量使用六氟化硫（SF6）示踪剂技术和钛白粉测定干物质摄入量（DMI）。与 NEL 相比，AN 在放牧期的总增重和平均日增重（ADG）均较高。AN 在育肥场的 ADG 较高，育肥期较短，导致胴体产量和胴体 ADG 增加。NEL 在放牧期的甲烷产量（kg/期）比 AN 低 19%（P<0.01），而在育肥场则没有差异。NEL 在放牧时的甲烷强度（CH4/BW）较低，但在育肥场的单位 ADG 产生的 CH4 较多。尽管育肥场的 DMI（kg/天）存在差异，但品种组成对两个阶段的 CH4 产量（CH4/DMI）没有影响。综上所述，在热带气候条件下，杂交可能是提高性能和减少每 ADG 甲烷的一种选择，从而降低每公斤肉产生的甲烷排放量。
