Differences between rumen outflow rate of fibrous and soybean meal particles in dry Chios ewes

Abstract

Fractional outflow rate (FOR) of Cr-mordanted soybean meal (SBM), berseem, alfalfa and barley forage was determined on four rumen-fistulated Chios ewes (Trial 1). In Trial 2, FOR of SBM and chopped or ground alfalfa was measured in six ewes. In both trials, SBM had greater FOR (Trial 1, P < 0.019; Trial 2, P < 0.001) than fibrous feeds. Differences among roughages were not significant. Grinding of alfalfa resulted in a small non-significant ( P > 0.1) increase in FOR compared with chopped alfalfa. It is concluded that FOR of mordanted SBM at a predetermined rate of intake is different from that of mordanted fibrous feeds. This suggests that values of FOR from mordanted fibrous feeds cannot be used to determine protein degradation of protein supplements. Furthermore, it is evident that more work is needed to determine whether the prediction of effective protein degradation of small particle forages rich in protein, can be based on FOR obtained with mordanted SBM, or whether there is need for FOR determination for specific fibrous feeds, especially when the latter comprise a considerable part of the total diet.