Bae Beomseok, Pope Logan, Park Kiyeon, Lee Chanhee
Department of Animal Sciences, The Ohio State University, Wooster, OH, USA.
Anim Biosci. 2025 Aug;38(8):1672-1679. doi: 10.5713/ab.25.0020. Epub 2025 Apr 11.
This in vitro study determined the combination effect of nitrate and lactate on nitrate reduction, rumen fermentation and methane production. We hypothesized that the combination decreases methane production and enhances nitrate reduction.
An in vitro batch culture was conducted to determine the 2 main factors of nitrate and lactate in 2×2 factorial arrangement: a basal diet (CON), the basal diet supplemented with nitrate (2.2% in dietary dry matter [DM]; Nit), lactate (2.2%; Lact), or the combination of nitrate and lactate (Nit-Lact). Rumen fluids from lactating Holstein cows were obtained and mixed with McDougall's buffer for the in vitro batch culture. Total gas production, methane production, pH, volatile fatty acid (VFA), NH3-N, NO3-N and NO2-N concentration, and DM digestibility were determined.
A trend of interaction between nitrate and lactate was observed for DM digestibility (p = 0.06), which occurred because DM digestibility tended to decrease for Nit compared with CON (42.2 vs. 45.3%) but did not for Nit-Lact. Nitrate decreased (p<0.05) methane (25.6 vs. 31.0 mL at 24 h) and total gas production (296 vs. 313 mL at 24 h). Total VFA production was not affected by treatments. However, nitrate increased the proportion of acetate (p<0.01) and decreased (p<0.01) proportions of propionate, butyrate and valerate at 24 h of incubation. However, lactate increased valerate at 24 h of incubation (p<0.01). The concentration of NO3-N for Nit-Lact was lower than that of Nit (41.2 vs. 51.0 mg/L; p<0.01) at 3 h of incubation.
Nitrate decreased methane production. The combination of nitrate and lactate had beneficial effects on DM digestibility and nitrate reduction, compared with nitrate alone although no interaction between nitrate and lactate was shown for VFA production and methane production. Changes in the major VFA by nitrate indicated that nitrate acted as an alternative electron acceptor to decrease methane production.
本体外研究确定了硝酸盐和乳酸对硝酸盐还原、瘤胃发酵及甲烷生成的联合作用。我们假设这种联合作用会减少甲烷生成并增强硝酸盐还原。
进行体外批次培养，以2×2析因设计确定硝酸盐和乳酸这两个主要因素：基础日粮（CON）、添加硝酸盐（占日粮干物质[DM]的2.2%；Nit）、乳酸（2.2%；Lact）或硝酸盐与乳酸的组合（Nit-Lact）的基础日粮。采集泌乳期荷斯坦奶牛的瘤胃液，并与麦克道格尔缓冲液混合用于体外批次培养。测定总产气量、甲烷产量、pH值、挥发性脂肪酸（VFA）、NH₃-N、NO₃-N和NO₂-N浓度以及DM消化率。
在DM消化率方面观察到硝酸盐和乳酸之间存在交互作用趋势（p = 0.06），这是因为与CON相比，Nit组的DM消化率有下降趋势（42.2%对45.3%），而Nit-Lact组没有。硝酸盐降低了（p<0.05）甲烷产量（24小时时为25.6毫升对31.0毫升）和总产气量（24小时时为296毫升对313毫升）。总VFA产量不受处理影响。然而，在培养24小时时，硝酸盐增加了乙酸比例（p<0.01），并降低了（p<0.01）丙酸、丁酸和戊酸的比例。然而，在培养24小时时乳酸增加了戊酸比例（p<0.01）。在培养3小时时，Nit-Lact组的NO₃-N浓度低于Nit组（41.2毫克/升对51.0毫克/升；p<0.01）。
硝酸盐降低了甲烷生成。与单独使用硝酸盐相比，硝酸盐和乳酸的组合对DM消化率和硝酸盐还原具有有益作用，尽管在VFA生成和甲烷生成方面未显示硝酸盐和乳酸之间存在交互作用。硝酸盐引起的主要VFA变化表明，硝酸盐作为替代电子受体减少了甲烷生成。
