Morphological fractions of maize stover harvested at different stages of grain maturity and nutritive value of different fractions of the stover

The proportion of different morphological fractions of maize stover was assessed at three stages of grain maturity and nutritive value of the morphological fractions was evaluated based on chemical composition, in sacco dry matter (DM) degradability and in vitro gas production. Stem proportion of the stover increased by 20%, whereas the proportions of tassel and leaf blades decreased by 41.5 and 44%, respectively, as grain moisture content dropped from about 30–10%. The crude protein (CP) content was highest in leaf blade and tassel. Leaf blade had the lowest neutral detergent fibre (NDF), acid detergent fibre (ADF) and cellulose contents and the highest ash, ADF-ash and total proanthocyanidins (TPA) contents. On the other hand, CP, ash, ADF-ash and TPA contents were lowest and the NDF content was highest in husk. Stem had the highest ADF, lignin and cellulose contents. erall in sacco DM degradability tended to be higher in leaf blades and lower in leaf sheaths than in the other morphological fractions. The washing loss was highest (p < 0.05) in stem and lowest in leaf blade and husk. On the other hand, leaf blade had significantly higher (p < 0.05) degradability of the water insoluble fraction than leaf sheath, stem and whole stover. The lag time was highest (p < 0.05) in stem and lowest in leaf blades. The morphological fractions differed in the volume of gas produced in the following order: husk > whole stover > stem > leaf sheath > leaf blade > tassel. Stem and whole stover showed rapid gas production in the early stage of fermentation, although the gas production rate of stem started to decline earlier than that of the other morphological fractions. Gas production due to fermentation of insoluble feed components, which mostly occurred between 6 and 24 h of incubation, was highest in husk. In vitro gas production and in sacco DM degradability could not rank the morphological fractions in a similar order which could be due to the effect of protein fermentation on gas production. Gas production showed an inverse relationship with CP, ash, ADF-ash and TPA contents of the morphological fractions.