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 viva 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-iota 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 composition, 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.