Concentrate supplementation: A way to mitigate enteric methane emissions in pregnant Hanwoo heifers

The objective of this study was to investigate the effect of supplementing concentrates in a forage-based diet on methane emissions of pregnant Hanwoo heifers.Twenty-one pregnant Hanwoo heifers (481 42.4 kg) were divided into two groups: 1) a group receiving forage only (control, CON) and 2) the other group receiving forage with 4 kg of a concentrate mix (treatment, TRT).Methane (CH 4 ) concentration was measured using a laser methane detector, following an 18-d adaptation period, according to previously established protocols.Feed intake was recorded throughout the experimental period.Ruminal fluid was collected and analyzed for pH, ammonia-nitrogen (NH 3 -N), and volatile fatty acid (VFA).The TRT exhibited higher dry matter and neutral detergent fiber intake than CON (p < 0.05) with elevated NH 3 -N (p < 0.001) and total VFA concentrations (p = 0.013).The proportions of butyrate, valerate, and iso-valerate were higher in TRT than CON (p < 0.05).Notably, CH 4 concentrations per kg dry matter intake was lower in the TRT group, both from respiration and eructation (p < 0.05).In conclusion, supplementing concentrates in a low-quality forage-based diet for pregnant Hanwoo heifers fulfills nutrient requirements and reduces CH 4 emissions, suggesting a potential strategy to reduce environmental impact of Hanwoo production.