Warner D, Bannink A, Hatew B, van Laar H, Dijkstra J
J Anim Sci. 2017 Aug;95(8):3687-3700. doi: 10.2527/jas.2017.1459.
The objective of this study was to determine the effect of level of feed intake and quality of ryegrass silage as well as their interaction on enteric methane (CH) emission from dairy cows. In a randomized block design, 56 lactating dairy cows received a diet of grass silage, corn silage, and a compound feed meal (70:10:20 on DM basis). Treatments consisted of 4 grass silage qualities prepared from grass harvested from leafy through late heading stage, and offered to dairy cows at 96 ± 2.4 (mean ± SEM) days in milk (namely, high intake) and 217 ± 2.4 d in milk (namely, low intake). Grass silage CP content varied between 124 and 286 g/kg of DM, and NDF content between 365 and 546 g/kg of DM. After 12 d of adaptation, enteric CH production of cows was measured in open-circuit climate-controlled respiration chambers for 5 d. No interaction between DMI and grass quality on CH emission, or on milk production, diet digestibility, and energy, and N retention was found ( ≥ 0.17). Cows had a greater DMI (16.6 vs. 15.5 kg/d; SEM 0.46) and greater fat- and protein-corrected milk (FPCM) yield (29.9 vs. 25.4 kg/d; SEM 1.24) at high than low intake (both ≤ 0.001). Apparent total-tract nutrient digestibility was not affected ( ≥ 0.08) by DMI level. Total enteric CH production (346 ± 10.9 g/d) was not affected ( = 0.15) by DMI level. A small, significant ( = 0.025) decrease at high compared with low intake occurred for CH yield (21.8 ± 0.59 g/kg of DMI; -4%). Methane emission intensity (12.8 ± 0.56 g/kg of FPCM; -12%) was considerably smaller ( ≤ 0.001) at high intake as a result of greater milk yields realized in early lactation. As grass quality decreased from leafy through late heading stage, FPCM yield and apparent total-tract OM digestibility declined (-12%; ≤ 0.015), whereas total CH production (+13%), CH yield (+21%), and CH emission intensity (+28%) increased ( ≤ 0.001). Our results suggest that improving grass silage quality by cutting grass at an earlier stage considerably reduces enteric CH emissions from dairy cows, independent of DMI. In contrast, losses of N in manure increased for the earlier cut grass silage treatments. The small increase in DMI at high intake was associated with a small to moderate reduction in CH emission per unit of DMI and GE intake. This study confirmed that enteric CH emissions from dairy cows at distinct levels of feed intake depend on the nutritive value and chemical composition of the grass silage.
本研究的目的是确定采食量水平和黑麦草青贮饲料质量及其交互作用对奶牛肠道甲烷（CH）排放的影响。采用随机区组设计，56头泌乳奶牛采食由青贮牧草、玉米青贮和复合饲料组成的日粮（干物质基础上比例为70:10:20）。处理包括4种由从叶期到抽穗后期收获的牧草制成的青贮饲料质量，并分别以产奶96±2.4（均值±标准误）天（即高采食量）和产奶217±2.4天（即低采食量）提供给奶牛。青贮牧草的粗蛋白（CP）含量在124至286克/千克干物质之间，中性洗涤纤维（NDF）含量在365至546克/千克干物质之间。适应12天后，在开路气候控制呼吸室中对奶牛的肠道CH产量进行5天的测量。未发现干物质采食量（DMI）和牧草质量在CH排放、产奶量、日粮消化率、能量及氮保留方面存在交互作用（P≥0.17）。高采食量时奶牛的DMI更高（16.6对15.5千克/天；标准误0.46），脂肪和蛋白质校正乳（FPCM）产量也更高（29.9对25.4千克/天；标准误1.24），低采食量时则相反（两者P≤0.001）。DMI水平对表观全消化道养分消化率无影响（P≥0.08）。DMI水平对总肠道CH产量（346±10.9克/天）无影响（P=0.15）。与低采食量相比，高采食量时CH产量（21.8±0.59克/千克DMI；-4%）有小幅显著下降（P=0.025）。由于泌乳早期产奶量更高，高采食量时的甲烷排放强度（12.8±0.56克/千克FPCM；-12%）显著更低（P≤0.001）。随着牧草质量从叶期到抽穗后期下降，FPCM产量和表观全消化道有机物消化率降低（-12%；P≤0.015），而总CH产量（+13%）、CH产量（+21%）和CH排放强度（+28%）增加（P≤0.001）。我们的结果表明，通过在较早阶段刈割牧草来提高青贮牧草质量可显著降低奶牛的肠道CH排放，且与DMI无关。相反，早期刈割青贮牧草处理的粪便中氮损失增加。高采食量时DMI的小幅增加与单位DMI和GE摄入量的CH排放小幅至中度减少有关。本研究证实，不同采食量水平下奶牛的肠道CH排放取决于青贮牧草的营养价值和化学成分。
