Differences in carbohydrate fractions between Lolium perenne and two tropical grasses of similar dry-matter digestibility

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Abstract
SUMMARY: Four samples each of Lolium perenne, Chloris gayana and Setaria splendida grown under similar conditions and having similar in vivo dry-matter digestibilities with sheep were used in a comparison of the chemical composition of tropical and temperate grass. L. perenne had less lignin, crude fibre, neutral-detergent fibre, acid-detergent fibre and cellulose than the two tropical grasses but more neutral-detergent solubles. In vivo digestibilities of the cell-wall polysaccharides of the tropical grasses were not reduced by their higher lignin contents. The digestibilities of the cell wall were generally higher than the digestibilities for the dry matter and neutral-detergent solubles. It is suggested that the effect of lignin on the digestibility of cell-wall polysaccharides is dependent on the area of protection, and better predictions may be achieved if the cell wall is divided into two fractions, an unlignified fraction that is completely digested and a completely indigestible fraction containing all the lignin.It is concluded that differences may be found in the carbohydrate composition of temperate and tropical grasses but that these differences may not cause differences in the overall in vivo digestibility of the dry matter.