Elwakeel E A, Titgemeyer E C, Johnson B J, Armendariz C K, Shirley J E
Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506-1600, USA.
J Dairy Sci. 2007 Nov;90(11):5226-36. doi: 10.3168/jds.2007-0305.
In vitro studies and a lactation trial were conducted to investigate the effects of fibrolytic enzyme mixtures at different inclusion amounts. Seven enzymes in amounts designed to mimic addition of 1, 5, 15, or 30 g/d to dairy diets were incubated in vitro with either soybean hulls or alfalfa for 24 or 48 h. Enzyme treatments generally increased in vitro dry matter disappearance (IVDMD), but not volatile fatty acid production. For some enzyme mixtures, lesser amounts of enzymes led to greater increases in IVDMD, whereas for others there were no differences among the amounts tested. The enzyme mixture with the most cellulase activity was the most effective enzyme in improving IVDMD. In additional in vitro experiments, the same enzymes were used at an amount of 5 g/d, as well as at other amounts that showed promising responses in the first trial. Preincubation of substrates with enzymes before fermentation also was tested. Alfalfa, soybean hulls, corn silage, and corn gluten feed were used as substrates. Preincubation of the substrate with enzymes for 18 h before in vitro fermentation improved IVDMD. The effect on substrate solubilization of incubating substrates with the enzymes but without rumen fluid was also studied. Addition of enzymes to substrates without subsequent fermentation did not solubilize significant amounts of dry matter, indicating that the positive effect of preincubation cannot be attributed directly to hydrolysis of substrates before the in vitro fermentation with ruminal microbes. The fibrolytic enzyme that appeared most promising in vitro did not affect lactational performance when fed to dairy cows.
开展了体外研究和一项泌乳试验，以调查不同添加量的纤维分解酶混合物的效果。将七种酶按设计量添加到奶牛日粮中，模拟每日添加1、5、15或30克，然后在体外与大豆皮或苜蓿一起孵育24或48小时。酶处理通常会提高体外干物质消失率（IVDMD），但不会提高挥发性脂肪酸产量。对于某些酶混合物，酶量较少会使IVDMD的增幅更大，而对于其他酶混合物，所测试的酶量之间没有差异。纤维素酶活性最高的酶混合物是提高IVDMD最有效的酶。在另外的体外实验中，使用了相同的酶，添加量为每日5克，以及在首次试验中显示出良好反应的其他添加量。还测试了在发酵前将底物与酶进行预孵育。使用苜蓿、大豆皮、玉米青贮和玉米麸质饲料作为底物。在体外发酵前将底物与酶预孵育18小时可提高IVDMD。还研究了在没有瘤胃液的情况下将酶与底物孵育对底物溶解的影响。在底物中添加酶但不进行后续发酵并不能溶解大量干物质，这表明预孵育的积极作用不能直接归因于在与瘤胃微生物进行体外发酵之前对底物的水解。在体外表现最有前景的纤维分解酶在喂给奶牛时对泌乳性能没有影响。
