Rumen degradation of straw. 10. Consistency of differences in nutritive value between varieties of cereal straws

The consistency of differences between varieties in nutritive value of cereal straws was tested over 3 years consecutively for nine varieties of spring barley and 10 varieties of winter wheat straw and over 2 years consecutively for 12 varieties of winter barley and six varieties of oats. For all varieties there were large year-to-year differences in nutritive value measured by ruminal degradation characteristics using the nylon bag technique. For spring barley there were large differences between varieties and the correlations between varieties in different years were mostly in excess of r = 0·90 for 48-h degradability and maximum potential degradability. For winter wheat the correlations between varieties for different years were lower but mostly significant. For the winter barley differences between varieties were less, but even so differences between varieties in different years were significant. For oats differences between the varieties were small and there was no significant correlation within varieties between years. The results suggest that the nutritive value of cereal straws is generally consistent between years and is a characteristic that could be improved by selection.