The chemical composition, digestibility and energy value of fermented and urea-treated whole crop wheat harvested at three stages of maturity

The metabolizable energy (ME) content, digestibility in vivo and chemical composition of fermented and urea-treated whole crop wheat (WCW) forage harvested were measured at different maturities. Over 2 years, twenty-four wheat forages (cv. Slepjner, Hussar and Cadenza) were harvested at 376, 516 and 632 g dry matter (DM) kg^?1 in Year 1 and 341, 467 and 544 g DM kg^?1 in Year 2 (Cuts 1, 2 and 3 respectively). Forages were conserved in 200?-ι barrels with or without a formic acid-based additive and with urea in Cuts 2 and 3 (20 or 40 g kg^?1 DM). Chemical compositions, digestibility in vivo and energy losses in faeces, urine and methane were measured in wethers fed 12 g DM kg^?1 live weight. Respective ranges in pH, crude protein, water-soluble carbohydrates, starch and neutral detergent fibre plus amylase (NDFA) contents were 3·8–8·5, 89–394, 2–43, 23–424 and 306–655 g kg^?1 DM. ME content, digestible organic matter content (DOMD) and digestibilities of starch and NDFA ranged between 8·4 and 15·7 MJ kg^?1 DM, 558 and 708 g kg^?1 DM, 0·901 and 0·999 and 0·362 and 0·693 respectively. Predicted methane energy losses were poorly correlated with measured values ( r ² < 0·45) in both years, but this accounted for less than 0.1 MJ ME kg^?1 DM. Significant ( P < 0.05) effects of maturity on the ME/DOMD ratio were observed and ascribed to differences in the extent of fermentation. Therefore, treatment application and maturity exert considerable influence on the ME content of WCW.