Stensig T, Robinson P H
Danish Institute of Agricultural Sciences, Research Centre Foulum, Tjele, Denmark.
J Dairy Sci. 1997 Jul;80(7):1339-52. doi: 10.3168/jds.S0022-0302(97)76062-4.
Four ruminally and duodenally cannulated Holstein cows in early lactation were fed alfalfa [47% neutral detergent fiber (NDF)] or timothy silage (49% NDF) for ad libitum intake in a 4 x 4 Latin square experiment. Forages were supplemented with 8 or 12 kg/d of an essentially fiber-free concentrate to study digestion and passage kinetics of forage fiber in high producing dairy cows. Fractional digestion and passage rates of NDF in the rumen were derived from ruminal pool sizes. Alfalfa had a potentially digestible NDF fraction with a faster rate of digestion but a larger indigestible NDF fraction and, consequently, higher physical fill in the rumen than did timothy. However, dry matter intake did not differ between forages, primarily because of the higher fractional passage rates of alfalfa NDF. Although dry matter intake was 23.2 kg/d, fractional passage rates of forage NDF were generally lower than those usually assumed. Fractional rates of NDF digestion decreased equally for both forages as concentrate in the diet increased, but diets with alfalfa forage had the smallest quantitative reduction because of the markedly smaller ruminal pool size of potentially digestible NDF. The fractional passage rate of NDF decreased as concentrate in the diet increased for diets containing alfalfa but did not change for diets containing timothy. Consequently, as concentrate in the diet increased, digestibilities of NDF in the rumen and whole tract increased with alfalfa and decreased with timothy. Results suggest that fiber-free concentrate is useful when digestion and passage kinetics of specific forage fibers are being measured in high producing dairy cows.
在一项4×4拉丁方试验中，给4头处于泌乳早期、安装了瘤胃和十二指肠瘘管的荷斯坦奶牛随意采食苜蓿（中性洗涤纤维含量为47%）或梯牧草青贮料（中性洗涤纤维含量为49%）。给草料补充8或12千克/天基本无纤维的精饲料，以研究高产奶牛中草料纤维的消化和通过动力学。瘤胃中中性洗涤纤维的分数消化率和通过率是根据瘤胃池大小得出的。与梯牧草相比，苜蓿具有可消化的中性洗涤纤维部分，消化速度更快，但不可消化的中性洗涤纤维部分更大，因此在瘤胃中的物理填充量更高。然而，两种草料的干物质摄入量没有差异，主要是因为苜蓿中性洗涤纤维的分数通过率更高。尽管干物质摄入量为23.2千克/天，但草料中性洗涤纤维的分数通过率通常低于通常假设的值。随着日粮中精饲料增加，两种草料的中性洗涤纤维分数消化率均同等下降，但含苜蓿草料的日粮中中性洗涤纤维的定量减少最小，因为可消化中性洗涤纤维的瘤胃池大小明显更小。对于含苜蓿的日粮，随着日粮中精饲料增加，中性洗涤纤维的分数通过率下降，但对于含梯牧草的日粮则没有变化。因此，随着日粮中精饲料增加，苜蓿日粮瘤胃和全消化道中中性洗涤纤维的消化率增加，而梯牧草日粮则下降。结果表明，在测定高产奶牛特定草料纤维的消化和通过动力学时，无纤维精饲料是有用的。
