In vivo and in vitro digestible fractions in forage

Faeces and the residues from the in vitro digestion of 13 forages were sequentially extracted with acid-pepsin, ethyl alcohol, hot water and diethyl ether and the quantity of the extracts was adjusted to a protein-free basis and expressed per 100 g of original forage organic matter. Undigested material inin vivo and in vitro experiments were respectively, 3·37 and 1·88 g (±0·12) for ethyl alcohol extracts, 1·13 and 1·10 g (±0·05) for hot water extracts, 0·15 and 0·12 g(±0·02) for diethyl ether extracts and 1·44 (±0·22) and 0g for 0·1 N -HCI extracts. The difference between values for in vivo and in vitro experiments was considered to represent endogenous material present in faeces.