Abstract
Simple SummaryReducing methane emissions from dairy cows is environmentally important. In this experiment, pasture fed dairy cows offered concentrates containing linseed oil emitted 18% less methane per kg of milk solids produced than those offered concentrates containing either stearic acid or soy oil. Additionally, cows fed linseed oil or soy oil produced more milk than those fed stearic acid. These results may contribute to the development of strategies to reduce methane emissions from pasture-based livestock whilst maintaining or improving animal productivity.Emissions of methane (CH4) from dairy production systems are environmentally detrimental and represent an energy cost to the cow. This study evaluated the effect of varying C18 fatty acid sources on CH4 emissions, milk production and rumen methanogen populations in grazing lactating dairy cows. Forty-five Holstein Friesian cows were randomly allocated to one of three treatments (n = 15). Cows were offered 15 kg dry matter (DM)/d of grazed pasture plus supplementary concentrates (4 kg DM/d) containing either stearic acid (SA), linseed oil (LO), or soy oil (SO). Cows offered LO and SO had lower pasture DM intake (DMI) than those offered SA (11.3, 11.5 vs. 12.6 kg/d). Cows offered LO and SO had higher milk yield (21.0, 21.3 vs. 19.7 kg/d) and milk protein yield (0.74, 0.73 vs. 0.67 kg/d) than those offered SA. Emissions of CH4 (245 vs. 293, 289 g/d, 12.4 vs. 15.7, 14.8 g/kg of milk and 165 vs. 207, 195 g/kg of milk solids) were lower for cows offered LO than those offered SA or SO. Methanobrevibacter ruminantium abundance was reduced in cows offered LO compared to SA. Offering supplementary concentrates containing LO can reduce enteric CH4 emissions from pasture fed dairy cows.
Highlights
Estimates of the contribution of animal agriculture to total global anthropogenic greenhouse gas (GHG) emissions, ranges from 7% to 18% [1,2]
Pasture DM intake (DMI) was higher (p = 0.02) for cows offered stearic acid (SA) compared to those offered soy oil (SO) or linseed oil (LO) which did not differ (p > 0.05)
Gross energy intake (GEI, MJ/d) was higher for cows offered SA compared to those offered SO or LO
Summary
Estimates of the contribution of animal agriculture to total global anthropogenic greenhouse gas (GHG) emissions, ranges from 7% to 18% [1,2]. Irish agricultural derived GHG emissions increased by 2.9% in 2015 [4] reflecting the national strategy to increase milk production and the subsequent increase in dairy cow numbers [5]. In temperate regions of the world, pasture-based dairy production systems are associated with low feed production costs [7] due to the competitive cost advantage of including grazed pasture in the diet [8]. Increasing the proportion of grazed pasture in the diet of the dairy cow is a key component of sustainability in an EU post quota environment [9]. Enhancing pasture quality reduces CH4 emissions from grazing systems [10–12], as the majority of pasture based dairy production systems in Ireland incorporate concentrate supplementation for at least part of the lactation [13], strategic manipulation of the chemical composition of supplemental concentrate offers further opportunity to reduce CH4 emissions. Potential to mitigate CH4 emissions via strategic lipid supplementation of grazed pasture diets [14] exists
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