King K J, Huber J T, Sadik M, Bergen W G, Grant A L, King V L
Department of Animal Sciences, University of Arizona, Tucson 85721.
J Dairy Sci. 1990 Nov;73(11):3208-16. doi: 10.3168/jds.S0022-0302(90)79012-1.
Six lactating Holstein cows, fitted with T-type cannulas in the proximal duodenum, were used in a replicated 3 x 3 Latin square design to determine influence of supplemental protein on amino acid profiles of duodenal chyme and plasma. Protein sources were blood meal, corn gluten meal, and cottonseed meal, which furnished approximately 46% of the total protein in corn-grain corn silage diets. Markers were 15N to estimate rumen bacteria and chromic oxide to estimate nutrient flow. Dry matter intake was lowest on blood meal. Duodenal flow of N exceeded N intake 23% on blood meal and corn gluten meal. Percentages of organic matter and protein digested in the rumen were 56.5, 41.8; 61.2, 53.4; and 50.6, 56.2 for the respective diets. Variation in patterns of amino acids flowing to the duodenum, but not in coccygeal blood, closely reflected dietary differences with six of eight essential amino acids highest for the same treatment in both diet and duodenal chyme. Essential amino acids in least abundance for milk production, measured by mammary extraction coefficients, differed among diets. We conclude that supplemental protein source influences greatly the quantity and pattern of amino acids available for digestion in lactating dairy cows.
选用6头装有十二指肠近端T型套管的泌乳期荷斯坦奶牛，采用重复的3×3拉丁方设计，以确定补充蛋白质对十二指肠食糜和血浆氨基酸谱的影响。蛋白质来源为血粉、玉米蛋白粉和棉籽粕，它们在谷物-玉米青贮饲料中提供约46%的总蛋白质。标记物为15N用于估计瘤胃细菌，氧化铬用于估计养分流量。血粉组的干物质采食量最低。血粉和玉米蛋白粉组十二指肠氮流量超过氮摄入量23%。各日粮瘤胃中有机物和蛋白质的消化率分别为56.5%、41.8%；61.2%、53.4%；50.6%、56.2%。流入十二指肠的氨基酸模式存在差异，但尾静脉血中的氨基酸模式无差异，这与日粮差异密切相关，8种必需氨基酸中有6种在日粮和十二指肠食糜中的同一处理组含量最高。通过乳腺提取系数测定，日粮中对产奶量而言丰度最低的必需氨基酸存在差异。我们得出结论，补充蛋白质来源对泌乳奶牛可用于消化的氨基酸数量和模式有很大影响。
