William H. Miner Agricultural Research Institute, Chazy, NY 12921.
Department of Veterinary Medicine, Università di Bologna, 40064 Bologna, Italy.
J Dairy Sci. 2021 Feb;104(2):1728-1743. doi: 10.3168/jds.2020-19088. Epub 2020 Dec 11.
The effect of neutral detergent fiber (NDF) degradability of corn silage in diets containing lower and higher NDF concentrations on lactational performance, nutrient digestibility, and ruminal characteristics in lactating Holstein cows was measured. Eight ruminally cannulated Holstein cows averaging 91 ± 4 (standard error) days in milk were used in a replicated 4 × 4 Latin square design with 21-d periods (7-d collection periods). Dietary treatments were formulated to contain either conventional (CON; 48.6% 24-h NDF degradability; NDFD) or brown midrib-3 (BM3; 61.1% 24-h NDFD) corn silage and either lower NDF (LNDF) or higher NDF (HNDF) concentration (32.0 and 35.8% of ration dry matter, DM) by adjusting the dietary forage content (52 and 67% forage, DM basis). The dietary treatments were (1) CON-LNDF, (2) CON-HNDF, (3) BM3-LNDF, and (4) BM3-HNDF. Data were analyzed as a factorial arrangement of diets within a replicated Latin square design with the MIXED procedure of SAS (SAS Institute Inc., Cary, NC) with fixed effects of NDFD, NDF, NDFD × NDF, period(square), and square. Cow within square was the random effect. Time and its interactions with NDFD and NDF were included in the model when appropriate. An interaction between NDFD and NDF content resulted in the HNDF diet decreasing dry matter intake (DMI) with CON corn silage but not with BM3 silage. Cows fed the BM3 corn silage had higher DMI than cows fed the CON corn silage, whereas cows fed the HNDF diet consumed less DM than cows fed the LNDF diet. Cows fed the BM3 diets had greater energy-corrected milk yield, higher milk true protein content, and lower milk urea nitrogen concentration than cows fed CON diets. Additionally, cows fed the BM3 diets had greater total-tract digestibility of organic matter and NDF than cows fed the CON diets. Compared with CON diets, the BMR diets accelerated ruminal NDF turnover. When incorporated into higher NDF diets, corn silage with greater in vitro 24-h NDFD and lower undegradable NDF at 240 h of in vitro fermentation (uNDF240) allowed for greater DMI intake than CON. In contrast, for lower NDF diets, NDFD of corn silage did not affect DMI, which suggests that a threshold level of inclusion of higher NDFD corn silage is necessary to observe enhanced lactational performance. Results suggest that there is a maximum gut fill of dietary uNDF240 and that higher NDFD corn silage can be fed at greater dietary concentrations.
研究了日粮中低、高中性洗涤纤维（NDF）降解率的玉米青贮对泌乳荷斯坦奶牛泌乳性能、养分消化率和瘤胃特性的影响。8 头瘤胃瘘管荷斯坦奶牛，泌乳天数平均为 91±4（标准误差），采用 4×4 拉丁方设计重复 21 天（7 天收集期）。日粮处理配方分别含有常规（CON；24 小时 NDF 降解率为 48.6%；NDFD）或棕色中脉 3（BM3；24 小时 NDFD 为 61.1%）玉米青贮和低 NDF（LNDF）或高 NDF（HNDF）浓度（日粮干物质的 32.0%和 35.8%，DM），通过调整日粮中粗饲料含量（DM 基础上的 52%和 67%）来实现。日粮处理分别为（1）CON-LNDF、（2）CON-HNDF、（3）BM3-LNDF 和（4）BM3-HNDF。数据分析采用 SAS（SAS Institute Inc.，Cary，NC）的 MIXED 程序，作为拉丁方设计内日粮的因子排列，具有 NDFD、NDF、NDFD×NDF、时期（平方）和平方的固定效应。方内的牛是随机效应。当合适时，将时间及其与 NDFD 和 NDF 的交互作用纳入模型中。NDFD 和 NDF 含量之间的相互作用导致 CON 玉米青贮的 HNDF 日粮降低了干物质采食量（DMI），而 BM3 青贮则没有。与 CON 玉米青贮相比，饲喂 BM3 玉米青贮的奶牛 DMI 更高，而饲喂 HNDF 日粮的奶牛 DM 摄入量低于饲喂 LNDF 日粮的奶牛。饲喂 BM3 日粮的奶牛比饲喂 CON 日粮的奶牛产奶量更高，乳真蛋白含量更高，乳尿素氮浓度更低。此外，与 CON 日粮相比，饲喂 BM3 日粮的奶牛对有机物和 NDF 的总肠道消化率更高。与 CON 日粮相比，BMR 日粮加速了瘤胃 NDF 的周转。当纳入更高 NDF 日粮时，体外 24 小时 NDFD 较高且体外发酵 240 小时时未降解 NDF 较低（uNDF240）的玉米青贮可使 DMI 摄入量高于 CON。相比之下，对于低 NDF 日粮，玉米青贮的 NDFD 不影响 DMI，这表明需要包含更高 NDFD 的玉米青贮的阈值水平才能观察到增强的泌乳性能。结果表明，膳食 uNDF240 的肠道填充有一个最大量，并且可以在更高的日粮浓度下饲喂具有更高 NDFD 的玉米青贮。
