Abstract
We evaluated the potential of feeding high-oil rapeseed cake or natural additives as rumen modifiers on enteric methane (CH4) emissions, nutrient utilization, performance, and milk fatty acid (FA) profile of dairy cows. Eight Nordic Red dairy cows averaging (mean ± SD) 81 ± 21 d in milk and 41.0 ± 1.9 kg of milk yield at the beginning of the study were randomly assigned to a replicated 4 × 4 Latin square design with 21-d periods. Treatments comprised grass silage-based diets (45:55 forage to concentrate ratio on dry matter basis) including (1) control containing 19.3% rapeseed meal (CON), (2) CON with full replacement of rapeseed meal with rapeseed cake (RSC), (3) supplementation of CON with 50 g/d of yeast hydrolysate product plus coniferous resin acid-based compound (YHR), and (4) supplementation of CON with 20 g/d of combination of garlic-citrus extract and essential oils in a pellet (GCE). Apparent total-tract digestibility was measured using total collection of feces, and CH4 emissions were measured in respiratory chambers on 4 consecutive days. Data collected during d 17 and 21 in each period were used for ANOVA analysis using a mixed model. Treatments did not affect dry matter intake (DMI), whereas feeding RSC increased crude protein and ether extract digestibility compared with the other diets. Emissions of CH4 per day, per kilogram of DMI, and per kilogram of energy-corrected milk, and gross energy intake were lower for RSC compared with other diets. We found no effect of YHR on daily CH4 emissions, whereas CH4 yield (g of CH4/kg of DMI or as percentage of gross energy intake) decreased with GCE compared with CON. Treatments did not influence energy balance. Further, RSC reduced the proportion of N intake excreted in feces, and YHR improved N balance compared with CON diet. Feeding RSC resulted in greatest yields of milk and energy-corrected milk, and feed efficiency. Relative to the CON diet, RSC decreased saturated FA by 10% in milk fat by increasing cis-monounsaturated FA but also increased the proportion of trans FA. Proportion of odd- and branched-chain FA increased with GCE and YHR compared with CON. We conclude that replacing rapeseed meal by rapeseed cake decreased CH4 emissions, whereas YHR or GCE had no effect on CH4 emissions in this study.
Highlights
Meeting the need to feed the constantly growing human population without deleterious impact on the environment is a global challenge
We found no effect of YHR on daily CH4 emissions, whereas CH4 yield (g of CH4/kg of dry matter intake (DMI) or as percentage of gross energy intake) decreased with garlic-citrus extract and essential oils (GCE) compared with containing 19.3% rapeseed meal (CON)
The rapeseed cake (RSC) diet reduced (P < 0.01) CH4 emissions, expressed per unit of feed intake, OM digested in the total tract, milk yield, or ECM yield relative to other diets, whereas the GCE diet reduced CH4 emissions expressed per unit of feed or energy intake compared with CON
Summary
Meeting the need to feed the constantly growing human population without deleterious impact on the environment is a global challenge. Ruminants are an important part of the food system because of their ability to convert feedstuffs unsuitable for human consumption into high-quality protein in milk and meat. They contribute to climate change, mainly by emitting methane (CH4), a potent greenhouse gas, as a product of rumen fermentation. Several nutritional and management strategies have been reported to be effective in mitigation of greenhouse gas emissions from ruminants (Knapp et al, 2014; Beauchemin et al, 2020). Lipid supplementation is one of the most promising tools to depress CH4 production from ruminants (Beauchemin et al, 2009; Bayat et al, 2018).
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