Teagasc, Animal and Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork, P61 C996, Ireland; School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, D04 N2E5, Ireland.
Teagasc, Animal and Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork, P61 C996, Ireland.
J Dairy Sci. 2021 Jul;104(7):8039-8049. doi: 10.3168/jds.2020-19618. Epub 2021 Apr 30.
Greenhouse gas (GHG) emissions and nitrogen (N) efficiencies were modeled for 2 genetic groups (GG) of Holstein-Friesian cows across 3 contrasting feeding treatments (FT). The 2 GG were (1) high economic breeding index (EBI) animals representative of the top 5% of cows nationally (elite) and (2) EBI representative of the national average (NA). The FT represented (1) generous feeding of pasture, (2) a slight restriction in pasture allowance, and (3) a high-concentrate feeding system with adequate pasture allowance. Greenhouse gas and N balance models were parameterized using outputs generated from the Moorepark Dairy Systems model, a stochastic budgetary simulation model, having integrated biological data pertaining to the 6 scenarios (2 GG × 3 FT) obtained from a 4-yr experiment conducted between 2013 and 2016. On a per hectare basis, total system GHG emissions were similar for both elite and NA across the 3 FT. Per unit of product, however, the elite group had 10% and 11% lower GHG emissions per kilogram of fat- and protein-corrected milk and per kilogram of milk solids (MSO; fat + protein kg), respectively, compared with the NA across the 3 FT. The FT incorporating high concentrate supplementation had greater absolute GHG emissions per hectare as well as GHG per kilogram of fat- and protein-corrected milk and MSO. The elite group had a slightly superior N use efficiency (N output/N input) and lower N surplus (N input - N output) compared with the NA group. The high concentrate FT had an inferior N use efficiency and a higher N surplus. The results of the current study demonstrate that breeding for increased EBI will lead to a general improvement in GHG emissions per unit of product as well as improved N efficiency. The results also illustrate that reducing concentrate supplementation will reduce GHG emissions, GHG emissions intensity, while improving N efficiency in the context of pasture-based dairy production.
温室气体（GHG）排放和氮（N）效率在荷斯坦-弗里生牛的 2 个遗传组（GG）中进行了建模，跨越了 3 个不同的饲养处理（FT）。这 2 个 GG 分别是：（1）高经济选育指数（EBI）动物，代表全国前 5%的奶牛（精英）；（2）EBI 代表全国平均水平（NA）。FT 代表（1）牧场的丰饲，（2）牧场允许量的轻微限制，以及（3）高浓缩物饲养系统，具有充足的牧场允许量。温室气体和 N 平衡模型是使用 Moorepark 奶牛系统模型生成的输出进行参数化的，该模型是一个随机预算模拟模型，集成了与 2013 年至 2016 年期间进行的 4 年实验相关的 6 种情景（2 GG×3 FT）的生物数据。以每公顷为基础，在 3 个 FT 中，精英组和 NA 组的总系统 GHG 排放相似。然而，与 NA 组相比，精英组每单位产品的 GHG 排放量分别降低了 10%和 11%，每公斤脂肪-和蛋白校正奶和每公斤牛奶固体（MSO；脂肪+蛋白 kg）。在包含高浓缩物补充的 FT 中，每公顷的绝对 GHG 排放量以及每公斤脂肪-和蛋白校正奶和 MSO 的 GHG 排放量更大。与 NA 组相比，精英组的 N 利用效率（N 输出/N 输入）略有提高，N 盈余（N 输入-N 输出）较低。高浓缩物 FT 的 N 利用效率较低，N 盈余较高。本研究的结果表明，选育增加 EBI 将导致单位产品 GHG 排放的普遍改善，以及 N 效率的提高。结果还表明，减少浓缩物补充将减少 GHG 排放、GHG 排放强度，同时提高基于牧场的奶牛生产中的 N 效率。
