Yang W Z, Beauchemin K A, Rode L M
Livestock Sciences Section, Research Centre Agriculture and Agri-Food Canada, Lethbridge, AB.
J Dairy Sci. 2002 Aug;85(8):1958-68. doi: 10.3168/jds.S0022-0302(02)74272-0.
Effects of ratio of alfalfa silage to alfalfa hay and forage particle size on nutrient intakes, site of digestion, rumen pools, and passage rate of ruminal contents were evaluated in a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. The diets consisted of 60% barley-based concentrate and 40% forage made up either of 50:50 or 25:75 of alfalfa silage:alfalfa hay and alfalfa hay was either chopped or ground. Lactating dairy cows surgically fitted with ruminal and duodenal cannulas were used and offered ad libitum access to a total mixed ration. Intakes of nutrients were increased by increasing ratio of silage to hay but were not affected by particle size of forage. Change in ratio of silage to hay of diets did not affect site and extent of digestion. However, increased forage particle size of the diets improved digestibility of fiber and N in the total tract, and as well as digestibility of organic matter, starch, and acid detergent fiber in the intestine. There was a shift of starch digestion from the rumen to the intestine when forage particle size was increased, although total digestion of starch was not changed. Ruminal microbial protein synthesis and microbial efficiency also improved with increasing forage particle size. Cows fed ground hay versus chopped hay had significantly lower rumen wet mass regardless of the ratio of silage to hay. Reduced forage particle size also lowered ruminal nutrient pool size for cows fed the high silage diet. Ruminal passage rates of liquid and solid were decreased by reducing the ratio of silage to hay, and retention time of solids in the total tract was shortened by reducing forage particle size. These results indicate that manipulating ratio of silage to hay in the diets of dairy cows changed feed intake but had little effect on digestion. In contrast, increased forage particle size in dairy cow diets improved fiber digestion and microbial protein synthesis in the rumen, and shifted starch digestion from the rumen to the intestine. Dietary particle size, expressed as physically effective neutral detergent fiber, was a reliable indication of ruminal microbial protein synthesis and nutrient digestion.
采用4×4拉丁方设计，处理按2×2析因排列，评估苜蓿青贮与苜蓿干草比例及饲草颗粒大小对营养物质摄入量、消化部位、瘤胃池以及瘤胃内容物通过率的影响。日粮由60%的大麦型精料和40%的饲草组成，饲草由50:50或25:75的苜蓿青贮:苜蓿干草构成，苜蓿干草要么切碎要么粉碎。使用手术安装了瘤胃和十二指肠瘘管的泌乳奶牛，自由采食全混合日粮。随着青贮与干草比例的增加，营养物质摄入量增加，但不受饲草颗粒大小的影响。日粮中青贮与干草比例的变化不影响消化部位和消化程度。然而，日粮中饲草颗粒大小增加提高了全消化道纤维和氮的消化率，以及肠道中有机物、淀粉和酸性洗涤纤维的消化率。当饲草颗粒大小增加时，淀粉消化从瘤胃转移到肠道，尽管淀粉的总消化量没有变化。随着饲草颗粒大小的增加，瘤胃微生物蛋白合成和微生物效率也得到提高。无论青贮与干草的比例如何，饲喂粉碎干草的奶牛与切碎干草的奶牛相比，瘤胃湿质量显著更低。对于饲喂高青贮日粮的奶牛，饲草颗粒大小减小也降低了瘤胃营养池大小。降低青贮与干草的比例会降低瘤胃液体和固体的通过率，减小饲草颗粒大小会缩短固体在全消化道的停留时间。这些结果表明，调整奶牛日粮中青贮与干草的比例会改变采食量，但对消化影响不大。相反，奶牛日粮中饲草颗粒大小增加可改善瘤胃中的纤维消化和微生物蛋白合成，并使淀粉消化从瘤胃转移到肠道。日粮颗粒大小，以物理有效中性洗涤纤维表示，是瘤胃微生物蛋白合成和营养物质消化的可靠指标。
J Appl Genet. 2011-1-29
Zotero 插件