LAUSR

The present factorial experiment tested the thawed rumen fluid from frozen rumen contents against fresh rumen fluid from the same slaughtered cattle to estimate in vitro degradation of rapeseed meal (RSM) and grass nuts (GN) as two contrasting feeds at various times. Fresh rumen fluid showed higher (P < 0.05) in vitro dry matter (DMD) and crude protein (CPD) degradation than the thawed rumen fluid at most incubation times. Significant differences (P < 0.05) were found between fresh and differently prepared thawed rumen fluids for mean degradation constants (a, b, c) and effective degradability (P 0.02 ) of feeds. While the thawed rumen fluids had lower (P < 0.01) degradation than the fresh rumen fluid, their degradation values correlated very well (R 2 ≥ 0.95) with those for the fresh rumen fluid. It appeared that the thawed rumen fluid can be used to predict in vitro degradation of the selected feeds when frequent access to slaughtered or fistulated animals is restricted. Nevertheless it would be vital to improve the activity of thawed rumen fluid prior to testing its suitability for numerous feeds before recommending its routine use to estimate degradation of ruminant feeds.