Yang W Z, Beauchemin K A
Agriculture and Agri-Food Canada, Research Centre, Lethbridge, Alberta T1J 4B1, Canada.
J Dairy Sci. 2005 Mar;88(3):1090-8. doi: 10.3168/jds.S0022-0302(05)72776-4.
Effects of physically effective (pe) neutral detergent fiber (NDF) content of dairy cow diets on nutrient intakes, site and extent of digestion, microbial protein synthesis and milk production were evaluated in a double 3 x 3 Latin square design using 6 lactating dairy cows with ruminal and duodenal cannulas. During each of 3 periods, cows were offered 1 of 3 diets that were chemically similar but varied in peNDF content (high, medium, and low) by altering corn silage particle length. The peNDF contents were determined using the Penn State Particle Separator and were 11.5, 10.3, and 8.9%, for the high, medium, and low diets, respectively, and the physical effectiveness factors for the long, medium, and fine silages were 84.1, 72.6, and 67.2%, respectively. Increased forage particle length increased intake of peNDF but did not affect intakes of nutrients including dry matter, NDF, starch, and nitrogen. Except for starch, apparent digestibilities of nutrients in the total tract were linearly increased with increasing dietary peNDF. Fiber digestion was affected by dietary peNDF to a greater extent than were the other nutrients. However, increased digestibility due to increased dietary peNDF did not significantly improve milk production or milk composition. Increased dietary peNDF also increased numerically rumen microbial protein synthesis due to increased amount of organic matter fermented in the rumen. These results indicate that increasing the peNDF content of a corn silage based diet improves digestibility, especially digestibility of fiber, in the total tract. Dietary particle size, expressed as peNDF, is positively associated with nutrient digestibility when level of peNDF in the diet is low.
采用双3×3拉丁方设计，使用6头装有瘤胃和十二指肠瘘管的泌乳奶牛，评估了奶牛日粮中物理有效（pe）中性洗涤纤维（NDF）含量对养分摄入量、消化部位和程度、微生物蛋白合成及产奶量的影响。在3个时期的每个时期，给奶牛提供3种日粮中的1种，这3种日粮化学组成相似，但通过改变玉米青贮颗粒长度使peNDF含量有所不同（高、中、低）。使用宾夕法尼亚州立颗粒分离器测定peNDF含量，高、中、低日粮的peNDF含量分别为11.5%、10.3%和8.9%，长、中、细青贮饲料的物理有效性因子分别为84.1%、72.6%和67.2%。饲草颗粒长度增加会使peNDF摄入量增加，但不影响包括干物质、NDF、淀粉和氮在内的养分摄入量。除淀粉外，全消化道养分的表观消化率随日粮peNDF增加呈线性增加。与其他养分相比，日粮peNDF对纤维消化的影响更大。然而，日粮peNDF增加导致的消化率提高并未显著改善产奶量或乳成分。日粮peNDF增加还会使瘤胃微生物蛋白合成在数值上增加，这是由于瘤胃中发酵的有机物质数量增加。这些结果表明，增加以玉米青贮为基础的日粮的peNDF含量可提高全消化道的消化率，尤其是纤维的消化率。当日粮中peNDF水平较低时，以peNDF表示的日粮颗粒大小与养分消化率呈正相关。
