02724naa a2200217 a 450000100080000000500110000800800410001910000210006024501550008126000090023652020620024565000250230765000180233265000110235065000260236165000200238765000130240765000140242065300130243477300590244717856452013-08-15       1965    bl ---       0--  u    #d1 aSOEST, P. J. van  aSymposium on factors influencing the voluntary intake of herbage by ruminantsbvoluntary intake in relation to chemical composition and digestibility.  c1965  aChemical composition on the whole is much more closely related to digestibility than VI. In some forage species (orchardgrass, brome grass, Sudangrass) the relation between VI and chemical components is very high, and NVI could be predicted with some accuracy in these situations. In other species (alfalfa, bluegrass, and perhaps timothy) relationships are confounded, and there is not a significant relationship between VI digestibility or between chemical composition and VI. The interrelationships between intake, digestibility and chemical composition are higly species-oriented. Tall fescue was consumed to a greater extent when mature. Results with two different sets of alfalfa from Utah and West Virginia agree in that there was not a consistent relationship between intake and digestibility or chemical composition. Positive relations between VI and lignin content can appear in at least two ways: rejection of immature forage because of palatability, taste or possibly toxic factors, or because of grass-legume interaction. In terms of chemical composition, the only consistent effect that can be observed for all forages is that of the total fibrous fraction, cell-wall constituents. As this fraction increases, voluntary intake declines with an increasingly negative slope. In forages with a low cell-wall content, digestibility and intake apparently are not related. In forages with a high cell-wall content, intake is higly correlated with both chemical composition and digestible dry matter. This suggests that the relationship between digestible dry matter and voluntary intake depends on the proportion of digestible energy from cell-wall constituents. These data are consistent with the theory that fiber mass inhibits intake in those forages with a high cell-wall content. The total fibrous part of legumes, represented by cell-wall constituents, does not appear to be large enough to inhibit intake. The point at which fiber mass appears to become limiting occurs when cell-wall content lies between 50 and 60% of the forage dry matter.  achemical composition  adigestibility  aforage  aComposição Química  aDigestibilidade  aForragem  aRuminante  aRuminant  tJournal of Animal Sciencegv.24, n.3, p.834-843, 1965.