Department of Animal Science, University of California, Davis 95616, USA.
J Anim Sci. 2011 Aug;89(8):2643-56. doi: 10.2527/jas.2010-3539. Epub 2011 Mar 11.
The term sustainable has many meanings, but in agriculture it generally refers to some balance between environmental, social, and economic goals. The objective of this project was to quantify inputs and outputs to assess the sustainability implications of 2 feedlot cattle management systems: Never Ever 3 (NE3) and a conventional (CON) system using metabolic modifiers. Angus-cross steers (n=104) were stratified by BW (337 kg ± 17) and randomly assigned to 4 pens per treatment group. The NE3 cattle received no feed additives or implants, whereas CON were implanted with 100 mg of trenbolone acetate and 14 mg of estradiol benzoate on d 1 and 70, and were additionally fed monensin [330 mg/(animal·d)] and tylosin phosphate [90 mg/(animal·d)] in their ration throughout the course of the study, and ractopamine hydrochloride at 254 mg/(animal·d) for the last 29 d on feed. Cattle were shipped on a constant average pen weight basis (596 kg ± 32 BW). The CON cattle had greater ADG (1.81 vs. 1.35 kg, P < 0.01) and were on feed fewer days (146 vs. 188 d, P < 0.01) than the NE3 cattle. No significant differences were observed in HCW (P = 0.072) or dressing percentage (P=0.62) between treatments (P > 0.05); however, CON carcasses averaged larger ribeye area (87 vs. 80 cm(2), P < 0.01), greater Warner-Bratzler shear force measurement (WBSF; 3.46 vs. 3.19 kg, P < 0.01), and smaller USDA marbling score (5.4 vs. 6.2, P < 0.01), and less backfat thickness (1.64 vs. 1.84 cm, P < 0.05) and yield grade (3.38 vs. 3.95, P < 0.01) than NE3 carcasses. Overall, CON cattle consumed 393 kg less DM in the feedlot (1,250 vs. 1,643 kg; P < 0.05). No treatment effects were observed for daily methane (CH(4); P=0.62) or nitrous oxide (N(2)O; P=0.7) emissions per steer. Assuming a constant emission rate on a DMI basis throughout the course of the feedlot trial, CON feedlot management resulted in a 31% decrease in emissions per finished steer compared with NE3 management. Expressing CH(4) emissions on a carbon dioxide equivalent (CO(2)-eq) basis revealed a 1.10-kg CO(2)-eq difference per kilogram BW gain (5.02 kg of NE3 vs. 3.92 kg of CON) between the 2 feedlot management systems. Although the metabolic modifiers resulted in additional costs for the CON treatment group, the cost per kilogram of feedlot BW gain was significantly less ($1.12/kg vs. $1.35/kg; P < 0.05) than NE3. Both production systems satisfied some sustainability criteria, although neither concurrently fulfilled all of the environmental, social, and economic goals of agricultural sustainability.
可持续性这个术语有多种含义，但在农业中，它通常是指在环境、社会和经济目标之间取得某种平衡。本项目的目的是量化投入和产出，以评估两种饲养场牛管理系统的可持续性影响：从不使用（NE3）和使用代谢调节剂的常规（CON）系统。 Angus-cross 阉牛（n=104）按体重（337 kg ± 17）分层，随机分配到每个处理组的 4 个围栏中。NE3 牛不使用饲料添加剂或植入物，而 CON 牛在第 1 天和第 70 天分别植入 100 mg 醋酸 trenbolone 和 14 mg 苯甲酸雌二醇，并在整个研究过程中在其日粮中添加莫能菌素[330 mg/（动物·d）]和泰乐菌素磷酸[90 mg/（动物·d）]，最后 29 d 每天添加 254 mg/（动物·d）盐酸莱克多巴胺。牛以恒定的平均围栏体重（596 kg ± 32 BW）运输。CON 牛的 ADG 更高（1.81 比 1.35 kg，P < 0.01），上料天数更少（146 比 188 d，P < 0.01）。处理间未观察到 HCW（P = 0.072）或出肉率（P=0.62）有显著差异（P > 0.05）；然而，CON 牛的肋眼面积更大（87 比 80 cm2，P < 0.01），WBSF 更高（3.46 比 3.19 kg，P < 0.01），USDA 大理石花纹评分更低（5.4 比 6.2，P < 0.01），背膘厚度更小（1.64 比 1.84 cm，P < 0.05），产肉等级更低（3.38 比 3.95，P < 0.01）。总体而言，CON 牛在饲养场消耗的干物质少 393 kg（1,250 比 1,643 kg；P < 0.05）。没有观察到每天甲烷（CH4）或氧化亚氮（N2O）排放量的处理效应（P=0.62）。假设在整个饲养场试验过程中，以干物质摄入量为基础，饲养场管理的排放量每头肥育牛减少 31%，与 NE3 管理相比。用二氧化碳当量（CO2-eq）表示 CH4 排放量，显示出每千克体重增加 2 个管理系统之间有 1.10 kg 的 CO2-eq 差异（5.02 kg 的 NE3 比 3.92 kg 的 CON）。尽管代谢调节剂使 CON 处理组的成本增加，但每千克肥育牛体重增加的成本明显较低（$1.12/kg 比 $1.35/kg；P < 0.05）。两种生产系统都满足了一些可持续性标准，尽管都没有同时满足农业可持续性的环境、社会和经济目标。
