Teagasc, Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork, Ireland; UCD School of Biosystems and Food Engineering, Agriculture & Food Science Centre, Belfield, Dublin 4, Ireland.
UCD School of Biosystems and Food Engineering, Agriculture & Food Science Centre, Belfield, Dublin 4, Ireland.
Animal. 2021 Jul;15(7):100247. doi: 10.1016/j.animal.2021.100247. Epub 2021 Jun 5.
Demand for beef produced from pasture-based diets is rising as it is perceived to be healthier, animal friendly and good for the environment. Animals reared on a solely grass forage diet, however, have a lower growth rate than cereal-fed animals and consequently are slaughtered at an older age. This study focused on the former by conducting life cycle assessments of beef production systems offering only fresh or conserved grass, and comparing them to a conventional pasture-based beef production system offering concentrate feeding during housing. The four suckler weanling-to-beef production systems simulated were: (i) Steers produced to slaughter entirely on a grass forage diet at 20 months (GO-20); (ii) Steers produced to slaughter entirely on a grass forage diet at 24 months (GO-24); (iii) Steers produced to slaughter on a grass forage diet with concentrate supplementation during housing (GC-24), and (iv) Steers produced to slaughter entirely on a grass forage diet at 28 months (GO-28). Two breed types were evaluated: early-maturing and late-maturing (LM). The environmental impacts assessed were global warming potential (GWP), non-renewable energy (NRE), acidification potential (AP), eutrophication potential (marine (MEP) and freshwater) were expressed per animal, per kg live weight gain (LWG), kg carcass weight gain, and kg meat weight gain (MWG). The GO-20 production system had the lowest environmental impact across all categories and functional units for both breeds. Extending age at slaughter increased environmental impact across all categories per animal. The LWG response of EM steers to concentrate feed supplementation in GC-24 was greater than the increase in total environmental impact resulting in GC-24 having a lower environmental impact across categories per kg product than GO-24. Concentrate feed supplementation had a similar effect on LM steers with the exception of NRE and AP. The increase in daily LWG in the third grazing season in comparison to the second grazing and housing resulted in GO-28 having lower GWP, NRE, AP, and MEP per kg product than GO-24. Early-maturing steers had lower environmental impact than LM when expressed per kg LWG. However the opposite occurred when impacts were expressed per kg MWG, despite LM steers producing the least LWG. The LM steers compensated for poor LWG performance by having superior carcass traits, which caused the breed to have the lowest environmental impact per kg MWG. The results reaffirms the importance of functional unit and suggests reducing the environmental impact of LWG does not always translate into improvements in the environmental performance of meat.
随着人们认为草饲牛肉更健康、更适合动物且对环境更友好，对其的需求正在上升。然而，仅以草料为食的动物生长速度比以谷物为食的动物慢，因此需要在更大的年龄时被屠宰。本研究通过对仅提供新鲜或保存的草或传统放牧基础的牛肉生产系统进行生命周期评估，专注于前者，比较了这两种系统的牛肉生产系统，该系统在育肥时提供浓缩饲料。模拟的四个犊牛断奶到牛肉生产系统分别为：（i）20 个月（GO-20）时完全以草料为食的育肥牛；（ii）24 个月（GO-24）时完全以草料为食的育肥牛；（iii）在育肥期间以草料和浓缩饲料饲养的育肥牛（GC-24）；（iv）28 个月（GO-28）时完全以草料为食的育肥牛。评估了两种品种类型：早熟和晚熟（LM）。评估的环境影响包括全球变暖潜势（GWP）、不可再生能源（NRE）、酸化潜势（AP）、富营养化潜势（海洋（MEP）和淡水），每头动物、每公斤活重增加（LWG）、公斤胴体重增加和公斤肉重增加（MWG）表示。GO-20 生产系统在所有类别和功能单位中对两种品种的环境影响都最低。屠宰年龄的延长增加了所有类别中每头动物的环境影响。EM 牛对 GC-24 中浓缩饲料的补充的 LWG 反应大于总环境影响的增加，导致 GC-24 在所有类别中的每公斤产品的环境影响都低于 GO-24。浓缩饲料对 LM 牛的影响与 NRE 和 AP 类似。与第二个放牧和育肥季节相比，第三个放牧季节的每日 LWG 增加导致 GO-28 的 GWP、NRE、AP 和 MEP 每公斤产品低于 GO-24。早熟牛的环境影响低于 LM，每公斤 LWG 表示。然而，当每公斤 MWG 表示时，情况则相反，尽管 LM 牛的 LWG 产量最低。LM 牛通过具有优越的胴体特性来弥补 LWG 性能不佳的情况，这导致该品种的每公斤 MWG 的环境影响最低。研究结果再次证实了功能单位的重要性，并表明减少 LWG 的环境影响并不总是会提高肉类的环境性能。
