The digestion of untreated and formaldehyde-treated soya-bean meals and estimation of their rumen degradabilities by different methods

SUMMARY The effect of treating soya-bean meal with formaldehyde was studied in cattle by supplementing a hay–barley diet with two levels of either untreated or formaldehydetreated soya-bean meal. The formaldehyde treatment had no significant effect upon apparent N digestibility in the whole tract; it increased the amounts of non-ammonia N and amino acid N entering the small intestine but this increase was not statistically significant. However, increasing the proportion of either soya-bean meal in the diet increased the flow of non-ammonia N to the small intestine and apparent N digestibility in the whole tract. The formaldehyde treatment reduced the apparent degradability of the soya-bean meal N, determined in vivo from 0·74 for the untreated meal to 0·38 for the formaldehyde-treated meal. The in sacco technique produced values for the apparent degradability of the two soya-bean meals which ranked them in a similar manner as did the in vivo technique but gave lower values for degradability than the in vivo technique.