Dairy and Food Science Department, South Dakota State University, Brookings 57007.
Dairy and Food Science Department, South Dakota State University, Brookings 57007; US Dairy Forage Research Center, USDA-Agricultural Research Service, Madison, WI 53706.
J Dairy Sci. 2019 Sep;102(9):7980-7996. doi: 10.3168/jds.2018-15771. Epub 2019 Jun 27.
The objective of this study was to investigate the effects of concentrations of forages and corn distillers dried grains with solubles (DDGS) on ruminal fermentation, ruminal kinetics, and total-tract digestibility of nutrients in lactating dairy cows. Four lactating Holstein cows with ruminal cannulas were assigned to a 4 × 4 Latin square in a 2 × 2 factorial arrangement of treatments. Diets were formulated to contain low forage [LF; 17% forage neutral detergent fiber (NDF)] or high forage (HF; 24.5% forage NDF) and DDGS at 0 or 18% (0DG or 18DG) of diet dry matter (DM). Intake of DM was not affected by the diets. Daily mean ruminal pH was affected by forage NDF × DDGS interactions, as the lowest ruminal pH was observed among cows fed LF18DG (6.02). Apparent total-tract digestibility for DM, organic matter, crude protein, NDF, acid detergent fiber, and starch was not affected by diets. Cows fed LF diets had a greater total volatile fatty acid concentration compared with cows fed HF (122 vs. 116 mM). Molar proportions of acetate were greater for HF compared with that of LF diets (62.6 vs. 57.5 mmol/100 mmol) and greater for 0DG diet compared with that of 18DG diets (61.3 vs. 58.7 mmol/100 mmol) diets. The molar proportion of propionate was affected by forage × DDGS interaction as the greatest propionate molar proportion was observed with cows fed LF18DG diet (27.7 mmol/100 mmol). Also, molar proportion of butyrate was affected by forage × DDGS interaction, as the greatest butyrate molar proportion was observed in cows fed HF18DG diet (13.5 mmol/100 mmol). Average fractional dilution rate for all diets was 11.9%/h and was not affected by diets. Fractional passage rate of the solid phase was greater for HF than for LF (4.40 vs. 3.76%/h). The ruminal retention time of solid phase was greater for LF compared with HF diets (27.3 vs. 23.3 h). Fractional passage rate of DDGS was affected by forage × DG interaction, as the highest fractional passage rate of DDGS was observed with cows fed HF18DG diet (7.72%/h). Our results demonstrated that concentrations of forage, DDGS, and their interaction influence ruminal degradation and kinetics of diets fed. Diets formulated at 17% forage NDF at 17% (DM basis) can decrease milk fat concentration compared with diets formulated at 25% forage NDF. Additionally, feeding DDGS at 18% DM basis to lactating dairy cows did not affect milk fat concentration or yield.
本研究旨在探讨饲粮中不同粗饲料和玉米干酒糟及其可溶物（DDGS）浓度对泌乳奶牛瘤胃发酵、瘤胃动力学和养分全肠道消化率的影响。选用 4 头带有瘤胃瘘管的泌乳荷斯坦奶牛，采用 2×2 因子设计的 4×4 拉丁方试验设计。试验设置低粗饲料（LF；17%中性洗涤纤维（NDF））或高粗饲料（HF；24.5% NDF）和 DDGS 0 或 18%（0DG 或 18DG）两种饲粮处理。饲粮干物质（DM）中 DDGS 的浓度不受奶牛采食的影响。奶牛的日平均瘤胃 pH 值受到粗饲料 NDF×DDGS 互作的影响，饲喂 LF18DG 日粮的奶牛瘤胃 pH 值最低（6.02）。DM、有机物、粗蛋白、NDF、酸性洗涤纤维和淀粉的全肠道表观消化率不受饲粮的影响。与 HF 日粮相比，LF 日粮组奶牛的总挥发性脂肪酸浓度更高（122 比 116 mM）。HF 日粮组的乙酸摩尔比例高于 LF 日粮组（62.6 比 57.5 mmol/100 mmol），0DG 日粮组的乙酸摩尔比例高于 18DG 日粮组（61.3 比 58.7 mmol/100 mmol）。丙酸摩尔比例受到粗饲料×DDGS 互作的影响，LF18DG 日粮组的丙酸摩尔比例最高（27.7 mmol/100 mmol）。丁酸摩尔比例也受到粗饲料×DDGS 互作的影响，HF18DG 日粮组的丁酸摩尔比例最高（13.5 mmol/100 mmol）。所有饲粮的平均固液比为 11.9%/h，不受饲粮的影响。HF 组奶牛的固体相通过速度快于 LF 组（4.40 比 3.76%/h）。LF 组奶牛的固体相瘤胃滞留时间长于 HF 组（27.3 比 23.3 h）。DDGS 的固液比通过速度受到粗饲料×DG 互作的影响，HF18DG 日粮组奶牛的 DDGS 固液比通过速度最高（7.72%/h）。研究结果表明，粗饲料、DDGS 及其互作的浓度影响饲粮的瘤胃降解和动力学。与含 25% NDF 的饲粮相比，以 17% NDF（DM 基础）为粗饲料浓度可降低乳脂浓度。此外，在泌乳奶牛的饲粮中添加 18% DM 基础的 DDGS 不会影响乳脂浓度或产量。
