Wattiaux M A, Mertens D R, Satter L D
US Dairy Forage Research Center, Agricultural Research Service, Madison.
J Dairy Sci. 1991 Nov;74(11):3872-83. doi: 10.3168/jds.S0022-0302(91)78580-9.
This experiment investigated the relationship between kinetics of digestion and change in specific gravity during in situ incubation. Nine cows were fed three sources of fiber (corn silage, alfalfa silage, or alfalfa hay) in diets formulated to contain 25, 30, or 35% NDF in three simultaneous 3 x 3 Latin squares. Method of alfalfa preservation did not influence rate of digestion or rate of increase in specific gravity of forage particles measured by a flotation technique. Prior to incubation, specific gravity of forage particles was in increasing order: alfalfa hay, alfalfa silage, and then corn silage. Essentially, all particles with a specific gravity less than 1.0 shifted to a higher specific gravity fraction by hydration within the first 4 h of incubation. From 4 to 56 h of incubation, percentage of residual DM that settled in solution having specific gravity of 1.3 increased linearly from 21 to 27% for corn silage but exponentially from 3 to 20% for alfalfa forages. Fractional rates of DM and NDF digestion and increase in percentage of residual DM having a specific gravity greater than 1.3 increased with the amount of fiber in the alfalfa diets and were correlated positively, suggesting that rate of increase in specific gravity, which affects rate of passage from the rumen, is influenced by rate of digestion of forage particles.
本实验研究了原位培养期间消化动力学与比重变化之间的关系。选用9头奶牛，采用3个同步的3×3拉丁方设计，给奶牛饲喂三种纤维来源（玉米青贮、苜蓿青贮或苜蓿干草）的日粮，日粮中中性洗涤纤维（NDF）含量分别为25%、30%或35%。苜蓿保存方法不影响通过浮选技术测定的饲草颗粒消化率或比重增加率。培养前，饲草颗粒的比重按升序排列为：苜蓿干草、苜蓿青贮，然后是玉米青贮。基本上，所有比重小于1.0的颗粒在培养的前4小时内通过水合作用转移到比重更高的部分。在培养4至56小时期间，比重为1.3的溶液中沉降的残余干物质百分比，玉米青贮从21%线性增加到27%，而苜蓿饲草则从3%呈指数增加到20%。苜蓿日粮中纤维含量增加时，干物质和中性洗涤纤维的消化率以及比重高于1.3的残余干物质百分比增加，且呈正相关，这表明影响瘤胃通过率的比重增加率受饲草颗粒消化率的影响。
