COMPOSITION AND IN-VITRO DIGESTIBILITY OF CARBOHYDRATES OF WHEAT PLANTS HARVESTED AT BLOOM AND SOFT-DOUGH STAGES

Wheat plants (Triticum aestivum) were harvested at the bloom and soft- dough stages, separated into leaves + sheaths, stems and spikes, and t he effect of stage of maturity on neutral detergent fibre (NDF) compos ition and degradability was studied. the accumulation of starch in the spikes compensated for the decrease in the degradability of NDF polys accharides so that the in-vitro digestibility of the organic matter (O M) was not changed between the bloom and soft-dough stages. Minor comp ositional changes occurred in the NDF of the various botanical fractio ns which can hardly explain the drop in NDF degradability with maturit y. There was a decline in the ratio of hemicellulose to lignin, and th e changes in NDF-monosaccharide degradability were probably related to the extension of covalent bonding between those matrix components dur ing maturation. Irrespective of botanical fraction and maturity stage, NDF xylose was less digestible than NDF glucose. Between bloom and so ft-dough stages there was an increase of 36% in the yield of digestibl e OM.