BOTANICAL FRACTIONS OF STRAW OF 51 CEREAL VARIETIES AND IN SACCO DEGRADABILITY OF VARIOUS FRACTIONS

Straws of 51 varieties of six kinds of cereal (oats, 12; spring barley, 6; winter barley, 10; winter rye, 9; winter wheat, 9; triticale, 5) were separated into the botanical fractions: internodes, leaves plus leaf sheath, nodes and chaff. Samples of all fractions were ground (2 mm) and incubated (48 h) in the rumen of five sheep each using the nylon bag technique. Sheep consumed 1000 g artificially dried grass and 200 g concentrate pre-mix per animal day-1. Straws of spring cereals contained a lower weight proportion of internodes (44%) and a greater weight proportion of leaves (39%) than straws of winter cereals (58% and 22%, respectively). High variations were observed among the fractions of various varieties (e.g. internodes: oats, 42.0-53.8%; spring barley, 36.0-45.0%; winter barley, 58.0-70.0%; winter rye, 57.0-69.0%; winter wheat, 46.0-58.0%; triticale, 41.9-57.1% of whole straw). In sacco degradability of leaves (spring cereal straw, 66%; winter cereal straw, 47%) and chaff (68% and 43%, respectively) was significantly higher than that of internodes (40% and 32%) and nodes (48% and 37%, respectively). High variations were found in the in sacco degradability of botanical fractions of various varieties. The following sequence of in sacco degradability of whole straw was mostly influenced by the proportion of fractions and their in sacco degradability: oats, 56.8 (49.2-65.4%); spring barley, 49.6 (46.1-54.2%); triticale, 42.4 (29.8-51.9%); winter wheat, 41.3 (36.7-45.9%); winter barley, 37.2 (33.6-44.9%); winter rye, 29.2 (25.5-35.6%). Grain yield was not significantly correlated with botanical weight proportions or in sacco degradability. Straw of spring cereals contains more leaves and is more degradable in the rumen than straw of winter cereals; therefore, it should be used primarily for feeding.