Lopes F, Cook D E, Combs D K
Department of Dairy Science, University of Wisconsin, Madison 53706.
Department of Dairy Science, University of Wisconsin, Madison 53706.
J Dairy Sci. 2015 Jan;98(1):574-85. doi: 10.3168/jds.2014-8661. Epub 2014 Nov 20.
An in vivo study was performed to validate an in vitro procedure that predicts rate of fiber digestion and total-tract neutral detergent fiber digestibility (TTNDFD). Two corn silages that differed in fiber digestibility were used in this trial. The corn silage with lower fiber digestibility (LFDCS) had the TTNDFD prediction of 36.0% of total NDF, whereas TTNDFD for the corn silage with higher fiber digestibility (HFDCS) was 44.9% of total neutral detergent fiber (NDF). Two diets (1 with LFDCS and 1 with HFDCS) were formulated and analyzed using the in vitro assay to predict the TTNDFD and rumen potentially digestible NDF (pdNDF) digestion rate. Similar diets were fed to 8 ruminally cannulated, multiparous, high-producing dairy cows in 2 replicated 4×4 Latin squares with 21-d periods. A 2×2 factorial arrangement of treatments was used with main effects of intake (restricted to approximately 90% of ad libitum intake vs. ad libitum) and corn silage of different fiber digestibility. Treatments were restricted and ad libitum LFDCS as well as restricted and ad libitum HFDCS. The input and output values predicted from the in vitro model were compared with in vivo measurements. The pdNDF intake predicted by the in vitro model was similar to pdNDF intake observed in vivo. Also, the pdNDF digestion rate predicted in vitro was similar to what was observed in vivo. The in vitro method predicted TTNDFD of 50.2% for HFDCS and 42.9% for LFDCS as a percentage of total NDF in the diets, whereas the in vivo measurements of TTNDFD averaged 50.3 and 48.6% of total NDF for the HFDCS and LFDCS diets, respectively. The in vitro TTNDFD assay predicted total-tract NDF digestibility of HFDCS diets similar to the digestibility observed in vivo, but for LFDCS diets the assay underestimated the digestibility compared with in vivo. When the in vitro and in vivo measurements were compared without intake effect (ad libitum and restricted) considering only diet effect of silage fiber digestibility (HFDCS and LFDCS), no differences were observed between methods. These values suggest that our in vitro TTNDFD model could be used to predicted rate of fiber digestion and NDF digestibility for dairy cattle.
进行了一项体内研究，以验证一种预测纤维消化率和全消化道中性洗涤纤维消化率（TTNDFD）的体外方法。本试验使用了两种纤维消化率不同的玉米青贮饲料。纤维消化率较低的玉米青贮饲料（LFDCS）的TTNDFD预测值为总中性洗涤纤维（NDF）的36.0%，而纤维消化率较高的玉米青贮饲料（HFDCS）的TTNDFD为总NDF的44.9%。使用体外分析法配制并分析了两种日粮（一种含LFDCS，一种含HFDCS），以预测TTNDFD和瘤胃潜在可消化NDF（pdNDF）消化率。将类似的日粮饲喂给8头安装了瘤胃瘘管的经产高产奶牛，采用2个重复的4×4拉丁方设计，每期21天。采用2×2析因处理安排，主要因素为采食量（限制在自由采食量的约90%与自由采食）和不同纤维消化率的玉米青贮饲料。处理组包括限制采食和自由采食的LFDCS以及限制采食和自由采食的HFDCS。将体外模型预测的输入和输出值与体内测量值进行比较。体外模型预测的pdNDF摄入量与体内观察到的pdNDF摄入量相似。此外，体外预测的pdNDF消化率与体内观察到的相似。体外方法预测日粮中HFDCS的TTNDFD为50.2%，LFDCS为42.9%（占总NDF的百分比），而体内测量的HFDCS和LFDCS日粮的TTNDFD平均分别为总NDF的50.3%和48.6%。体外TTNDFD分析预测HFDCS日粮的全消化道NDF消化率与体内观察到的消化率相似，但对于LFDCS日粮，该分析与体内相比低估了消化率。当仅考虑青贮饲料纤维消化率（HFDCS和LFDCS）的日粮效应，不考虑采食量效应（自由采食和限制采食）比较体外和体内测量值时，两种方法之间未观察到差异。这些值表明，我们的体外TTNDFD模型可用于预测奶牛的纤维消化率和NDF消化率。
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