Romero J J, Zarate M A, Adesogan A T
Department of Animal Sciences, Institute of Food and Agricultural Sciences, University of Florida, Gainesville 32608.
Department of Animal Sciences, Institute of Food and Agricultural Sciences, University of Florida, Gainesville 32608.
J Dairy Sci. 2015 Jan;98(1):406-17. doi: 10.3168/jds.2014-8285. Epub 2014 Oct 30.
Our objectives were to evaluate the effects of the dose rates of 5 Trichoderma reesei and Aspergillus oryzae exogenous fibrolytic enzymes (EFE; 1A, 2A, 11C, 13D, and 15D) on in vitro digestibility, fermentation characteristics, and preingestive hydrolysis of bermudagrass haylage and to identify the optimal dose of each EFE for subsequent in vitro and in vivo studies. In experiment 1, EFE were diluted in citrate-phosphate buffer (pH 6) and applied in quadruplicate in each of 2 runs at 0× (control), 0.5×, 1×, 2×, and 3×; where 1× was the respective manufacturer-recommended dose (2.25, 2.25, 10, 15, and 15g of EFE/kg of dry matter). The suspension was incubated for 24h at 25°C and for a further 24h at 39°C after the addition of ruminal fluid. In experiment 2, a similar approach to that in experiment 1 was used to evaluate simulated preingestive effects, except that sodium azide (0.02% wt/vol) was added to the EFE solution. The suspension was incubated for 24h at 25°C and then 15mL of water was added before filtration to extract water-soluble compounds. For both experiments, data for each enzyme were analyzed separately as a completely randomized block design with a model that included effects of EFE dose, run, and their interaction. In experiment 1, increasing the EFE dose rate nonlinearly increased the DM digestibility of 1A, 2A, 11C, and 13D and the neutral detergent fiber digestibility (NDFD) of 1A, 2A, 11C, and 13D. Optimal doses of 1A, 2A, 11C, 13D, and 15D, as indicated by the greatest increases in NDFD at the lowest dose tested, were 2×, 2×, 1×, 0.5×, and 0.5×, respectively. Increasing the dose rate of 2A, 11C, and 13D nonlinearly increased concentrations of total volatile fatty acids and propionate (mM), decreased their acetate-to-propionate ratios and linearly decreased those of samples treated with 1A and 15D. In experiment 2, increasing the dose rate of each EFE nonlinearly decreased concentrations of netural detergent fiber; also, increasing the dose rate of 1A, 2A, 11C, and 1D nonlinearly increased concentrations of water-soluble carbohydrates and free ferulic acid (μg/g). Application of increasing doses of the EFE increased NDF hydrolysis, NDFD, and ruminal fluid fermentation of bermudagrass haylage, but the optimal dose varied with the EFE.
我们的目标是评估5种里氏木霉和米曲霉外源纤维分解酶（EFE；1A、2A、11C、13D和15D）的剂量率对百慕大草青贮饲料的体外消化率、发酵特性和采食前水解的影响，并确定每种EFE用于后续体外和体内研究的最佳剂量。在实验1中，将EFE在柠檬酸 - 磷酸盐缓冲液（pH 6）中稀释，并在0×（对照）、0.5×、1×、2×和3×的剂量下进行两次重复实验，其中1×为各自制造商推荐的剂量（2.25、2.25、10、15和15克EFE/千克干物质）。加入瘤胃液后，悬浮液在25°C下孵育24小时，然后在39°C下再孵育24小时。在实验2中，采用与实验1类似的方法评估模拟采食前的效果，不同之处在于向EFE溶液中添加了叠氮化钠（0.02%重量/体积）。悬浮液在25°C下孵育24小时，然后在过滤前加入15毫升水以提取水溶性化合物。对于这两个实验，每种酶的数据分别作为完全随机区组设计进行分析，模型包括EFE剂量、实验批次及其相互作用的影响。在实验1中，增加EFE剂量率会使1A、2A、11C和13D的干物质消化率以及1A、2A、11C和13D的中性洗涤纤维消化率（NDFD）呈非线性增加。在测试的最低剂量下，1A、2A、11C、13D和15D的NDFD增加幅度最大时所对应的最佳剂量分别为2×、2×、1×、0.5×和0.5×。增加2A、11C和13D的剂量率会使总挥发性脂肪酸和丙酸（毫摩尔）浓度呈非线性增加，降低其乙酸与丙酸的比例，而1A和15D处理的样品中该比例呈线性下降。在实验2中，增加每种EFE的剂量率会使中性洗涤纤维浓度呈非线性下降；此外，增加1A、2A、11C和1D的剂量率会使水溶性碳水化合物和游离阿魏酸（微克/克）浓度呈非线性增加。增加EFE剂量会提高百慕大草青贮饲料的NDF水解、NDFD和瘤胃液发酵，但最佳剂量因EFE而异。
