Cherney D J, Mertens D R, Moore J E
ARS, U.S. Dairy Forage Res. Center, Madison, WI 53706.
J Anim Sci. 1991 Jan;69(1):413-22. doi: 10.2527/1991.691413x.
Objectives of this study were 1) to measure small-particle and liquid mean retention time (MRT) of 12 grass hays similar in NDF (61.3 +/- 1.9% NDF) but differing in morphological composition and to relate passage rates to proportions of blade, sheath and stem and 2) to evaluate the influence of MRT of small and large blade and stem fractions and large sheath fractions, in addition to morphological composition, on intake and digestibility of the 12 hays. In each of two periods, 24 sheep (wethers) were offered one of 12 hays at three consecutive levels of feeding: (L1) ad libitum, allowing 15% refusal; (L2) restricted to 100% of hay consumed ad libitum by an individual wether during L1; and (L3) 1.8% of BW on a DM basis. Hays offered included two sorghum-sudan, four barley, four oat and two pearl millet. Marked particles were pulse-dosed in L2 and L3. Large and small particles of stem and leaf were extracted with neutral detergent and marked with Cr or rare earth metals. Marked large and small stem particle MRT generally were longer (P less than .05) than those of corresponding large and small blade particles. Large sheath particles generally had an intermediate (P less than .05) MRT between those of large stem and blade particles. Mean retention times of marked fractions were lower (P less than .05) in L2 than in L3. Small particle MRT in L2 was longer than MRT for liquid, though correlations were high (r = .74 to .86, P less than .01). Large particles were retained longer than small particles. Particle size, morphology, and percentage of stem in the forage influenced the mean retention time. Use of representative samples of all fractions fed to measure retention times may lead to a better understanding of ruminal function and to improvements in explanations of intake regulation, because marked fractions do not behave identically for all forages.
1）测定12种中性洗涤纤维含量相近（中性洗涤纤维含量为61.3±1.9%）但形态组成不同的禾本科干草中小颗粒和液体的平均滞留时间（MRT），并将通过速率与叶片、叶鞘和茎的比例相关联；2）除形态组成外，评估小叶片、大叶片、茎部大组分和叶鞘大组分的平均滞留时间对这12种干草采食量和消化率的影响。在两个时期中的每个时期，给24只绵羊（阉羊）提供12种干草中的一种，采用三个连续的饲喂水平：（L1）自由采食，允许15%的剩料；（L2）限制在L1期间个体阉羊自由采食的干草量的100%；以及（L3）基于干物质的体重的1.8%。提供的干草包括两种高粱-苏丹草、四种大麦、四种燕麦和两种珍珠粟。在L2和L3水平下对明显的颗粒进行脉冲投给。用中性洗涤剂提取茎和叶的大、小颗粒，并用铬或稀土金属进行标记。标记的大、小茎颗粒的平均滞留时间通常比相应的大、小叶片颗粒的平均滞留时间长（P<0.05）。大的叶鞘颗粒的平均滞留时间通常介于大的茎颗粒和叶片颗粒之间（P<0.05）。标记组分的平均滞留时间在L2水平下低于（P<0.05）L3水平。L2水平下小颗粒的平均滞留时间比液体的平均滞留时间长，尽管相关性很高（r=0.74至0.86，P<0.01）。大颗粒比小颗粒滞留时间长。饲料中的颗粒大小、形态和茎的比例影响平均滞留时间。使用饲喂的所有组分的代表性样品来测量滞留时间，可能会更好地理解瘤胃功能，并改进对采食量调节的解释，因为标记组分在所有饲料中的行为并不相同。
