Agriculture and Agri-Food Canada, Sherbrooke Research and Development Centre, 2000 College Street, Sherbrooke, QC, Canada J1M 0C8.
Agriculture and Agri-Food Canada, Sherbrooke Research and Development Centre, 2000 College Street, Sherbrooke, QC, Canada J1M 0C8.
J Dairy Sci. 2021 Nov;104(11):11686-11698. doi: 10.3168/jds.2021-20466. Epub 2021 Aug 11.
This study was conducted to examine the effect of method of diet delivery to dairy cows on enteric CH emission, milk production, rumen fermentation, nutrient digestion, N excretion, and manure CH production potential. Sixteen lactating cows were used in a crossover design (35-d period) and fed ad libitum twice daily a diet [52:48, forage:concentrate ratio; dry matter (DM) basis] provided as forages and concentrates separately (CF) or as a total mixed ration (TMR). For the CF treatment, concentrates were offered first followed by mixed forages 45 min afterward. Method of diet delivery had no effect on DM intake, but neutral detergent fiber (NDF) intake was greater when the diet was delivered as TMR as compared with CF. Apparent total-tract digestibility of DM, crude protein, and gross energy was slightly (1 percentage unit) lower when the diet was offered as TMR than when offered as CF. In contrast, NDF digestibility was greater when the cows were fed TMR versus CF. Although average daily ruminal pH was not affected by method of diet delivery, daily duration of ruminal pH <5.6 was less when the diet was delivered as TMR as compared with CF (0.9 h/d versus 3.7 h/d). Delivering the diet as TMR increased ruminal total volatile fatty acid and NH concentrations, but had no effect on acetate, propionate, or branched-chain volatile fatty acid molar proportions. Yields of milk, milk fat, or milk protein, and milk production efficiency (kg of milk/kg of DM intake or g of N milk/g of N intake) were not affected by the method of diet delivery. Daily production (g/d), yield (% gross energy intake), and emission intensity (g/kg of energy-corrected milk) of enteric CH averaged 420 g/d, 4.9%, and 9.6 g/kg and were not affected by diet delivery method. Fecal N output was greater when the diet was delivered as TMR versus CF, whereas urinary N excretion (g/d, % N intake) was not affected. Manure volatile solids excretion and maximal CH production potential were not affected by method of diet delivery. Under the conditions of this study, delivering the diet as concentrates and forages separately versus a total mixed ration had no effect on milk production, enteric CH energy losses, urinary N, or maximal manure CH emission potential. However, feeding the diet as total mixed ration compared with feeding concentrates and forages separately attenuated the extent of postprandial decrease in ruminal pH, which has contributed to improving NDF digestibility.
本研究旨在探讨奶牛日粮的饲喂方式对肠道 CH 排放、牛奶产量、瘤胃发酵、养分消化、N 排泄和粪便 CH 产生潜力的影响。16 头泌乳奶牛采用交叉设计（35 天），自由采食两次/d，日粮[52:48，粗饲料：精饲料比；干物质（DM）基础]分别作为粗饲料和精饲料提供（CF）或作为全混合日粮（TMR）。对于 CF 处理，先提供精饲料，45 min 后再混合粗饲料。日粮的饲喂方式对 DM 摄入量没有影响，但与 CF 相比，TMR 提供的日粮中中性洗涤纤维（NDF）摄入量更大。当以 TMR 形式提供日粮时，DM、粗蛋白和总能的表观全肠道消化率略低（1 个百分点），而当以 CF 形式提供日粮时，NDF 消化率更高。虽然平均日瘤胃 pH 不受日粮饲喂方式的影响，但与 CF 相比，TMR 提供的日粮中 pH<5.6 的日持续时间更少（0.9 h/d 与 3.7 h/d）。以 TMR 形式提供日粮增加了瘤胃总挥发性脂肪酸和 NH 的浓度，但对乙酸、丙酸或支链挥发性脂肪酸摩尔比例没有影响。牛奶产量、乳脂或乳蛋白以及牛奶生产效率（kg 牛奶/kgDM 摄入量或 gN 牛奶/gN 摄入量）不受日粮饲喂方式的影响。肠道 CH 的日产生量（g/d）、产量（%总能量摄入量）和排放强度（g/kg 校正能量牛奶）平均为 420 g/d、4.9%和 9.6 g/kg，不受日粮饲喂方式的影响。与 CF 相比，TMR 提供的日粮时粪便 N 输出量更大，而尿 N 排泄量（g/d，%N 摄入量）不受影响。粪便挥发性固体排泄量和最大 CH 产生潜力不受日粮饲喂方式的影响。在本研究条件下，以精饲料和粗饲料分别提供日粮与全混合日粮相比，对牛奶产量、肠道 CH 能量损失、尿 N 或最大粪便 CH 排放潜力没有影响。然而，与分别提供精饲料和粗饲料相比，以全混合日粮形式提供日粮减轻了餐后瘤胃 pH 下降的程度，这有助于提高 NDF 消化率。
