Hall M B, Mertens D R
US Dairy Forage Research Center, USDA-ARS, Madison, WI 53706, USA.
J Dairy Sci. 2008 Jan;91(1):301-7. doi: 10.3168/jds.2006-689.
Selected vessel types and conditions used for in vitro fermentation were compared to evaluate their effects on determinations of neutral detergent fiber (NDF) digestibility (NDFD) in 2 replicate 48-h fermentations. Treatments included 50-mL polyethylene centrifuge tubes with gas-release valves (treatment 1); 50-mL polyethylene centrifuge tubes with continuous gassing with CO2 (treatment 2); 50-mL polyethylene centrifuge tubes sealed, oriented horizontally, and shaken continuously parallel to the long axis of the tube, with manual gas release (treatment 3); 125-mL Erlenmeyer flasks with continuous gassing with CO2 (treatment 4); and 125-mL serum vials sealed with stoppers and crimp seals with (treatment 5) or without (treatment 6) manual gas release. Goering and Van Soest medium and blended ruminal inoculum from 4 lactating cows were used. Substrates were alfalfa hay, corn silage, ryegrass hay, and soyhulls. Gas was released and measured in treatments 3 and 6 at 3.0, 5.5, 9.0, 11.5, 23.5, 29.5, and 47.5 h by using a syringe with a hypodermic needle. Vessels from each treatment were harvested at 0, 6, 12, 24, 30, and 48 h for NDF analysis, with NDFD calculated as 1 - [(residual NDF, g - residual NDF in fermentation blank, g)/sample NDF, g]. Medium pH did not decline below 6.3 for any treatment. Average values for NDFD for 24 through 48 h were 0.576, 0.639, 0.688, 0.668, 0.679, and 0.681 for treatments 1 through 6, respectively (standard error of the difference = 0.008). The lowest NDFD was noted for treatment 1, which differed from all other treatments; treatments 3, 4, 5, and 6 did not differ by treatment or by the interaction of treatment and substrate. Treatments 1 and 2 gave lower NDFD values than the other treatments, but these differences were not consistent and differed by substrate, with alfalfa showing the fewest differences among treatments and soyhulls the most. Net energy of lactation values for substrates, as predicted from differences in 48-h NDFD, were 7 to 15% lower for treatment 1 than for the average of all other treatments. Slopes of the gas production per gram of substrate dry matter curves differed between treatments 3 and 5. In conclusion, measured NDFD was altered by fermentation treatment, with polyethylene tubes + gas-release valves giving the lowest values. Consequently, NDFD values may not be comparable across fermentation methods, but the effect will vary among feedstuffs. The combination of methods used for sealing, gassing, or agitating vessels may have a greater impact on NDFD than does vessel type.
比较了用于体外发酵的选定容器类型和条件，以评估它们对两次重复的48小时发酵中中性洗涤纤维（NDF）消化率（NDFD）测定的影响。处理包括：带气体释放阀的50毫升聚乙烯离心管（处理1）；持续通入二氧化碳的50毫升聚乙烯离心管（处理2）；密封、水平放置并沿管的长轴连续摇动且手动释放气体的50毫升聚乙烯离心管（处理3）；持续通入二氧化碳的125毫升锥形瓶（处理4）；用塞子和压接密封密封且（处理5）或不（处理6）手动释放气体的125毫升血清瓶。使用了戈林和范·索est培养基以及来自4头泌乳奶牛的混合瘤胃接种物。底物为苜蓿干草、玉米青贮、黑麦草干草和豆皮。在处理3和6中，在3.0、5.5、9.0、11.5、23.5、29.5和47.5小时使用带皮下注射针头的注射器释放并测量气体。每个处理的容器在0、6、12、24、30和48小时收获用于NDF分析，NDFD计算为1 - [（残留NDF，克 - 发酵空白中的残留NDF，克）/样品NDF，克]。任何处理的培养基pH均未降至6.3以下。处理1至6在24至48小时的NDFD平均值分别为0.576、0.639、0.688、0.668、0.679和0.681（差异标准误 = 0.008）。处理l的NDFD最低，与所有其他处理不同；处理3、4、5和6在处理或处理与底物的相互作用方面没有差异。处理1和2的NDFD值低于其他处理，但这些差异不一致且因底物而异，苜蓿在处理之间的差异最小，豆皮差异最大。根据48小时NDFD的差异预测，处理1的底物泌乳净能值比所有其他处理的平均值低7%至15%。处理3和5每克底物干物质的产气量曲线斜率不同。总之，发酵处理会改变测得的NDFD，带气体释放阀的聚乙烯管给出的值最低。因此，不同发酵方法的NDFD值可能不可比，但影响因饲料而异。用于密封、通气或搅拌容器的方法组合对NDFD的影响可能比容器类型更大。
