Animal Genetics and Breeding Unit (AGBU), University of New England, Armidale, NSW, 2351, Australia.
NSW Department of Primary Industries, Livestock Industries Centre, Armidale, 2351, Australia.
Genet Sel Evol. 2019 Apr 29;51(1):18. doi: 10.1186/s12711-019-0459-5.
Societal pressures exist to reduce greenhouse gas (GHG) emissions from farm animals, especially in beef cattle. Both total GHG and GHG emissions per unit of product decrease as productivity increases. Limitations of previous studies on GHG emissions are that they generally describe feed intake inadequately, assess the consequences of selection on particular traits only, or examine consequences for only part of the production chain. Here, we examine GHG emissions for the whole production chain, with the estimated cost of carbon included as an extra cost on traits in the breeding objective of the production system.
We examined an example beef production system where economic merit was measured from weaning to slaughter. The estimated cost of the carbon dioxide equivalent (CO-e) associated with feed intake change is included in the economic values calculated for the breeding objective traits and comes in addition to the cost of the feed associated with trait change. GHG emission effects on the production system are accumulated over the breeding objective traits, and the reduction in GHG emissions is evaluated, for different carbon prices, both for the individual animal and the production system.
Multiple-trait selection in beef cattle can reduce total GHG and GHG emissions per unit of product while increasing economic performance if the cost of feed in the breeding objective is high. When carbon price was $10, $20, $30 and $40/ton CO-e, selection decreased total GHG emissions by 1.1, 1.6, 2.1 and 2.6% per generation, respectively. When the cost of feed for the breeding objective was low, selection reduced total GHG emissions only if carbon price was high (~ $80/ton CO-e). Ignoring the costs of GHG emissions when feed cost was low substantially increased emissions (e.g. 4.4% per generation or ~ 8.8% in 10 years).
The ability to reduce GHG emissions in beef cattle depends on the cost of feed in the breeding objective of the production system. Multiple-trait selection will reduce emissions, while improving economic performance, if the cost of feed in the breeding objective is high. If it is low, greater growth will be favoured, leading to an increase in GHG emissions that may be undesirable.
社会压力要求减少来自农场动物的温室气体（GHG）排放，尤其是在肉牛中。随着生产力的提高，总 GHG 和单位产品的 GHG 排放量都会减少。以前关于 GHG 排放的研究存在的局限性是，它们通常不能充分描述饲料摄入量，仅评估选择对特定性状的后果，或者仅检查生产链的一部分后果。在这里，我们检查整个生产链的 GHG 排放，其中包括将碳的估计成本作为生产系统的育种目标中特征的额外成本。
我们检查了一个示例的牛肉生产系统，该系统从断奶到屠宰都以经济价值来衡量。与饲料摄入量变化相关的二氧化碳当量（CO-e）的估计成本包含在为育种目标特征计算的经济价值中，并且除了与特征变化相关的饲料成本之外。GHG 排放对生产系统的影响在育种目标特征上累积，并且针对不同的碳价格，针对单个动物和生产系统评估减少 GHG 排放的效果。
如果育种目标中的饲料成本较高，则肉牛的多性状选择可以减少总 GHG 和单位产品的 GHG 排放量，同时提高经济性能。当碳价格为 10 美元，20 美元，30 美元和 40 美元/吨 CO-e 时，选择分别使每代的总 GHG 排放量减少 1.1％，1.6％，2.1％和 2.6％。当育种目标中的饲料成本较低时，仅当碳价格较高（~80 美元/吨 CO-e）时，选择才会减少总 GHG 排放量。如果忽略饲料成本较低时的 GHG 排放成本，排放量将大大增加（例如，每代增加 4.4％或 10 年内增加 8.8％）。
减少肉牛 GHG 排放的能力取决于生产系统的育种目标中的饲料成本。如果育种目标中的饲料成本较高，则多性状选择将减少排放，同时提高经济性能。如果成本较低，则将有利于更大的生长，从而导致 GHG 排放增加，这可能是不可取的。
