Provimi Holding B.V., Research Centre De Viersprong, Veilingweg 23, NL-5334LD, Velddriel, the Netherlands.
J Dairy Sci. 2011 Aug;94(8):4028-38. doi: 10.3168/jds.2011-4236.
Feeding nitrate to dairy cows may lower ruminal methane production by competing for reducing equivalents with methanogenesis. Twenty lactating Holstein-Friesian dairy cows (33.2±6.0 kg of milk/d; 104±58 d in milk at the start of the experiment) were fed a total mixed ration (corn silage-based; forage to concentrate ratio 66:34), containing either a dietary urea or a dietary nitrate source [21 g of nitrate/kg of dry matter (DM)] during 4 successive 24-d periods, to assess the methane-mitigating potential of dietary nitrate and its persistency. The study was conducted as paired comparisons in a randomized design with repeated measurements. Cows were blocked by parity, lactation stage, and milk production at the start of the experiment. A 4-wk adaptation period allowed the rumen microbes to adapt to dietary urea and nitrate. Diets were isoenergetic and isonitrogenous. Methane production, energy balance, and diet digestibility were measured in open-circuit indirect calorimetry chambers. Cows were limit-fed during measurements. Nitrate persistently decreased methane production by 16%, whether expressed in grams per day, grams per kilogram of dry matter intake (DMI), or as percentage of gross energy intake, which was sustained for the full experimental period (mean 368 vs. 310±12.5 g/d; 19.4 vs. 16.2±0.47 g/kg of DMI; 5.9 vs.4.9±0.15% of gross energy intake for urea vs. nitrate, respectively). This decrease was smaller than the stoichiometrical methane mitigation potential of nitrate (full potential=28% methane reduction). The decreased energy loss from methane resulted in an improved conversion of dietary energy intake into metabolizable energy (57.3 vs. 58.6±0.70%, urea vs. nitrate, respectively). Despite this, milk energy output or energy retention was not affected by dietary nitrate. Nitrate did not affect milk yield or apparent digestibility of crude fat, neutral detergent fiber, and starch. Milk protein content (3.21 vs. 3.05±0.058%, urea vs. nitrate respectively) but not protein yield was lower for dietary nitrate. Hydrogen production between morning and afternoon milking was measured during the last experimental period. Cows fed nitrate emitted more hydrogen. Cows fed nitrate displayed higher blood methemoglobin levels (0.5 vs. 4.0±1.07% of hemoglobin, urea vs. nitrate respectively) and lower hemoglobin levels (7.1 vs. 6.3±0.11 mmol/L, urea vs. nitrate respectively). Dietary nitrate persistently decreased methane production from lactating dairy cows fed restricted amounts of feed, but the reduction in energy losses did not improve milk production or energy balance.
给奶牛饲喂硝酸盐可能会通过与产甲烷作用竞争还原当量来降低瘤胃甲烷的产生。20 头泌乳荷斯坦-弗里森奶牛（33.2±6.0 千克/天；试验开始时产奶 104±58 天）在连续 4 个 24 天的时期内分别饲喂含有日粮尿素或日粮硝酸盐源（21 克硝酸盐/千克干物质（DM））的全混合日粮（以玉米青贮为主；粗饲料与精饲料的比例为 66:34），以评估日粮硝酸盐的甲烷减排潜力及其持久性。该研究采用随机设计的配对比较进行，重复测量。在试验开始时，根据胎次、泌乳阶段和产奶量对奶牛进行分组。4 周的适应期使瘤胃微生物适应日粮尿素和硝酸盐。日粮的能量和氮含量相同。在闭路间接测热室中测量甲烷产生、能量平衡和日粮消化率。在测量期间，奶牛进行限量饲喂。硝酸盐持续降低 16%的甲烷产生量，无论是以每天克数、每千克干物质摄入量（DMI）克数还是以总能摄入量的百分比表示，这一效果在整个实验期间都得到了维持（平均值 368 比 310±12.5 克/天；19.4 比 16.2±0.47 克/千克 DMI；5.9 比 4.9±0.15%的总能摄入量分别为尿素和硝酸盐）。与硝酸盐的理论甲烷减排潜力（完全潜力=28%甲烷减少）相比，这种减少量较小。减少甲烷引起的能量损失导致饲料能量摄入向可代谢能量的转化率提高（57.3 比 58.6±0.70%，分别为尿素和硝酸盐）。尽管如此，日粮硝酸盐并不影响牛奶能量输出或能量保留。硝酸盐不影响牛奶产量或粗脂肪、中性洗涤纤维和淀粉的表观消化率。日粮硝酸盐降低了牛奶蛋白含量（3.21 比 3.05±0.058%，分别为尿素和硝酸盐），但不影响蛋白产量。在最后一个实验期间，测量了早、下午挤奶之间的氢气产生量。饲喂硝酸盐的奶牛产生了更多的氢气。饲喂硝酸盐的奶牛的血液高铁血红蛋白水平较高（0.5 比 4.0±1.07%的血红蛋白，分别为尿素和硝酸盐），血红蛋白水平较低（7.1 比 6.3±0.11 毫摩尔/升，分别为尿素和硝酸盐）。给限制饲喂的泌乳奶牛饲喂硝酸盐会持续降低甲烷的产生，但能量损失的减少并没有改善产奶量或能量平衡。
