CONTEXT

Demand for environmentally sustainable produced beef, especially ‘grass-fed’, is rising. Bull-beef production is a desirable alternative to steers due to large inherent growth and feed efficiency advantages. Compared to conventional indoor high-concentrate diets, pasture-finishing of bulls is low-cost, but carcass fat cover may not meet market requirements.

OBJECTIVE

We evaluated the performance, meat quality, profitability, greenhouse gas (GHG) emissions, and human-edible protein (HEP) efficiency of pasture-based purchased suckler bull ‘weanling’-to-beef finishing systems compared to an indoor high-concentrate system.

METHODS

Suckler bulls, initially offered grass silage and supplementary concentrates during a ‘backgrounding’ phase, were assigned to one of four finishing systems: grazed grass with three levels of barley-based concentrate, 0 (G-0), 0.25 (G-25), and 0.50 (G-50) of predicted dietary dry matter intake, or ad libitum concentrates and grass silage (ALC). The experimental data generated were used to parameterise a whole-farm systems model and the output, profitability and GHG emissions of ‘purchased weanling’-to-beef finishing systems were evaluated.

RESULTS AND CONCLUSIONS

Total daily dry matter intake was highest for ALC and lowest for G-0. Carcasses from ALC were heavier (406 kg) than all grazing systems; G-50 was heavier (387 kg) than G-25 and G-0 (367 kg). Carcass fat score was higher for ALC (8.3, scale 1–15) than the grazing systems, which were similar (5.0–5.6). Meat eating quality did not differ between systems. Although carcass output per hectare increased by 50% for G-50 and almost-doubled for ALC compared to G-0, gross and net margins were similar for G-0 and G-50, and considerably less for ALC. The GHG emission per animal were lowest for G0 and highest for G50; however, when expressed relative to live-, carcass-, and especially meat weight, emission intensities (kg CO₂eq) were lowest for ALC (5.4, 14.9, and 12.2, respectively) and highest for G-0 and G-25 (~9.6, 19.4, and 20.8, respectively). The HEP efficiency ratio was highest for G-0 (0.67) and lowest for ALC (0.21). Compared to a high-concentrate indoor bull finishing system, temperate pasture-based systems had lighter, ‘under-finished’ carcasses but similar meat eating quality, were more profitable, had superior HEP efficiency, but greater GHG emissions when expressed relative to live-, carcass-, and meat weight gain.

SIGNIFICANCE

Although carcasses were ‘under-finished’ for the grazing systems compared to the high-concentrate indoor system, meat eating quality was similar, implying that, potentially, there is greater scope for beef producers to operate relatively more profitable pasture-based bull-beef finishing. In view of the inverse relationships between profitability, HEP efficiency, and GHG emissions per unit of product among different suckler weanling-to-beef finishing systems, consideration of unavoidable trade-offs is necessary from a beef production, policy and future-research perspective.

中文翻译：

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与室内高浓度断奶到牛肉育成系统相比，以牧场为基础的乳牛的性能、肉质、盈利能力和温室气体排放

语境

对环境可持续生产的牛肉，尤其是“草食”牛肉的需求正在上升。由于巨大的固有生长和饲料效率优势，公牛生产是阉割的理想替代品。与传统的室内高浓缩日粮相比，公牛的放牧成本较低，但胴体脂肪覆盖率可能无法满足市场需求。

客观的

我们评估了与室内高浓缩系统相比，以牧场为基础购买的乳牛“断奶”到牛肉精加工系统的性能、肉类质量、盈利能力、温室气体 (GHG) 排放和人类食用蛋白质 (HEP) 效率.

方法

最初在“背景”阶段提供草青贮饲料和补充浓缩物的乳牛公牛被分配到四个整理系统之一：放牧草与三个级别的大麦浓缩物，0 (G-0)、0.25 (G-25) , 和 0.50 (G-50) 的预计膳食干物质摄入量，或随意选择的浓缩物和青贮饲料 (ALC)。生成的实验数据用于参数化整个农场系统模型，并评估“购买断奶”到牛肉育成系统的产量、盈利能力和温室气体排放量。

结果和结论

ALC 的每日总干物质摄入量最高，G-0 最低。来自 ALC 的胴体比所有放牧系统都重（406 公斤）；G-50 比 G-25 和 G-0（367 公斤）重（387 公斤）。ALC 的胴体脂肪评分（8.3，等级 1-15）高于放牧系统，两者相似（5.0-5.6）。肉食质量在系统之间没有差异。尽管与 G-0 相比，G-50 的每公顷胴体产量增加了 50%，ALC 几乎翻了一番，但 G-0 和 G-50 的毛利率和净利润率相似，而 ALC 的毛利率要低得多。每只动物的温室气体排放量 G0 最低，G50 最高；然而，当相对于活体、胴体，尤其是肉的重量表示时，排放强度（kg CO ₂eq) ALC 最低（分别为 5.4、14.9 和 12.2），而 G-0 和 G-25 最高（分别约为 9.6、19.4 和 20.8）。G-0 (0.67) 的 HEP 效率比最高，ALC (0.21) 最低。与高浓度室内公牛育成系统相比，基于温带牧场的系统具有更轻、“未完成”的屠体，但肉食质量相似，利润更高，HEP 效率更高，但相对于活牛而言，温室气体排放量更大。 ，胴体和肉的重量增加。

意义

尽管与高浓度室内系统相比，放牧系统的胴体“未完成”，但肉食质量相似，这意味着牛肉生产商可能有更大的空间经营相对更有利可图的牧场牛牛肉精加工。鉴于不同乳牛断奶到牛肉育成系统之间的盈利能力、HEP 效率和单位产品温室气体排放之间的反比关系，从牛肉生产、政策和未来研究的角度考虑不可避免的权衡是必要的。