STUDIES ON IN-SITU DEGRADATION OF FEEDS IN THE RUMEN .3. THE EFFECT OF FREEZING FORAGES BEFORE AND AFTER RUMEN INCUBATION

Freezing forages before rumen incubation and the in situ residues post incubation has become standard practice, but few results have been pub lished regarding the effects of freezing on in situ dry-matter degrada bility (DMdeg). Two studies were undertaken to investigate the effect of freezing following rumen incubation. In the first study, hay and pr efrozen silage were assessed and in the second the effect of prefreezi ng of silage was also compared Three mature rumen-cannulated cows were fed a diet consisting of silage and barley (80:20 DM basis). The sequ ence of bag incubation was such that all bags were removed from the ru men at the same time and could either be washed immediately or frozen (similar to 20 degrees C) for 54 h before washing. Freezing bags after rumen incubation, before washing was not found to have an effect on D Mdeg in study 1, but in study 2 reduced mean DMdeg and effective degra dability of silage (P = 0.014 and P = 0.009, respectively) were observ ed Silage frozen prior to rumen incubation was also found to have lowe r effective degradability values than silage not frozen before rumen i ncubation (P = 0.006) and the lag time of silage not prefrozen was lon ger than any other treatment It was concluded that freezing can signif icantly affect the DM degradability characteristics measured in situ b ut that the effects are small and of limited practical significance. C rown Copyright (C) 1997 Published by Elsevier Science B.V.