CONTEXT

Sheep production industries face the challenge of increasing farm production and profit while reducing environmental impacts.

OBJECTIVES

Genetic selection using multi-trait breeding indices can be used to improve flock productivity, profitability, and greenhouse gas (GHG) emissions intensities (kg CO₂-eq /kg of product), however validation of the improved performance of animals ranked higher on breeding indices at a flock level is required.

METHODS

Phenotypic data from 387,580 production records of animals born between 2018 and 2020 of known genetic merit in commercial flocks were inputted to an established bio-economic model. Two contrasting flocks were compared, a flock of ewes ranked High (top 20%) on the Irish replacement Index bred with rams ranked High on the replacement and terminal indices, and a flock of ewes ranked Low (bottom 20%) on the Irish replacement Index bred with rams ranked Low on the replacement and terminal indices. The two flocks were then simulated using life cycle assessment to estimate the GHG emissions profile for both systems.

RESULTS AND CONCLUSION

Flock weaning rates were 1.70 and 1.53 lambs weaned per ewe presented for breeding for the High and Low genetic merit flocks, respectively. The flock of High genetic merit ewes sold 0.17 more lambs per ewe, equating to 3.29 kg more lamb carcass per ewe, than the flock of Low genetic merit ewes; lambs from the High genetic merit flock were also sold at an earlier age. The greater production of the High genetic merit flocks resulted in an additional €18/ewe net profit than the Low genetic merit flock. Although total flock GHG emissions were higher for the High genetic merit flock, GHG emissions intensities were lower at 21.7 and 23.3 kg CO₂-eq /kg lamb carcass sold for the High and Low genetic merit flocks, respectively. The lower emissions intensity of the High genetic merit flock was due to the dilution effect of higher lamb production and lambs being drafted for slaughter ealier.

SIGNIFICANCE

The results suggest Irish sheep producers can make substantial profit gains through selection according to the national breeding indices while also reducing their environmental impact, and farmers should consider genetic merit when purchasing their rams, particularly sires of replacement ewe lambs.

中文翻译：

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对遗传价值不同的爱尔兰羊群的生产、利润和温室气体排放进行建模

语境

绵羊生产行业面临着在减少环境影响的同时增加农场产量和利润的挑战。

目标

使用多性状育种指数进行遗传选择可用于提高鸡群生产力、盈利能力和温室气体 (GHG) 排放强度（kg CO ₂ -eq /kg 产品），但验证动物性能的提高在育种中排名较高需要鸡群级别的索引。

方法

将 2018 年至 2020 年间出生的具有已知遗传价值的商业鸡群中 387,580 条生产记录的表型数据输入到已建立的生物经济模型中。比较了两个对比的鸡群，一群母羊在爱尔兰替代指数中排名高（前 20%），与公羊在替代指数和终端指数中排名高，一群母羊在爱尔兰替代指数中排名低（底部 20%）用公羊饲养的指数在替换指数和终端指数上排名较低。然后使用生命周期评估对这两个鸡群进行模拟，以估计两个系统的温室气体排放情况。

结果与结论

每只母羊断奶的羊群断奶率分别为 1.70 和 1.53 只羔羊，分别用于繁育高遗传价值鸡群和低遗传价值鸡群。高遗传价值母羊群比低遗传价值母羊群多售出 0.17 只羔羊，相当于每只母羊多售出 3.29 公斤的羔羊胴体；来自高遗传价值羊群的羔羊也在较早的年龄出售。与低遗传价值鸡群相比，高遗传价值鸡群的更高产量导致每只母羊额外增加 18 欧元的净利润。尽管高鸡群的总温室气体排放量较高遗传价值鸡群，温室气体排放强度较低，分别为高和低遗传价值鸡群出售的21.7 和 23.3 kg CO _{2 -eq /kg 羔羊胴体。}高遗传价值羊群的较低排放强度是由于较高的羔羊产量和较早被挑选用于屠宰的羔羊的稀释效应。

意义

结果表明，爱尔兰绵羊生产者可以通过根据国家育种指数进行选择来获得可观的利润，同时还可以减少对环境的影响，农民在购买公羊时应考虑遗传价值，尤其是替代母羊羔羊的公羊。