Wang W, Larsen M, Weisbjerg M R, Hellwing A L F, Lund P
Department of Animal and Veterinary Sciences, AU Viborg-Research Centre Foulum, Aarhus University, DK 8830 Tjele, Denmark.
JDS Commun. 2024 May 17;5(6):558-562. doi: 10.3168/jdsc.2023-0541. eCollection 2024 Nov.
The objective of this study was to investigate the effect of nitrate supplementation on diurnal enteric methane (CH) and nitrous oxide (NO) emissions in dairy cows. Four Danish Holstein dairy cows fitted with ruminal cannulas were used in a 2 × 2 crossover design with 2 periods of 14 d duration. Cows were fed ad libitum with 2 experimental diets based on either urea or nitrate (8.6 g of supplementation. Samples of ruminal fluid, blood, and rumen headspace gas samples were collected. Gas exchange was measured in respiration chambers during a 96-h period. Emission of NO was calculated from the ratio between CH and NO in the rumen headspace and the measured CH emission. Nitrate supplementation resulted in a lower daily CH production (g/d), CH yield (g/kg of DMI), and CH per kilogram of fat- and protein-corrected milk yield; a tendency of lower CH intensity (g/kg ECM); and higher daily hydrogen (H) production, H yield, and daily NO production compared with urea supplementation. The only difference in ruminal VFA composition was a higher valerate proportion in cows receiving nitrate compared with urea supplementation. In conclusion, nitrate compared with urea supplementation reduced CH production, mainly just after feeding, but also increased NO production.
本研究的目的是调查补充硝酸盐对奶牛日间肠道甲烷（CH）和一氧化二氮（N₂O）排放的影响。选用4头装有瘤胃瘘管的丹麦荷斯坦奶牛，采用2×2交叉设计，共2个为期14天的阶段。给奶牛自由采食两种基于尿素或硝酸盐的试验日粮（补充8.6克 ）。采集瘤胃液、血液和瘤胃顶空气体样本。在呼吸室中测量96小时内的气体交换。根据瘤胃顶空CH与N₂O的比例以及测得的CH排放量计算N₂O排放量。与补充尿素相比，补充硝酸盐导致每日CH产量（克/天）、CH产量（克/千克干物质采食量）和每千克脂肪和蛋白质校正乳产量的CH降低；CH强度（克/千克能量校正乳）有降低趋势；每日氢气（H₂）产量、H₂产量和每日N₂O产量更高。瘤胃挥发性脂肪酸（VFA）组成的唯一差异是，与补充尿素相比，补充硝酸盐的奶牛中戊酸比例更高。总之，与补充尿素相比，补充硝酸盐可降低CH产量，主要在喂食后不久，但也会增加N₂O产量。
