The yield of dry matter (DM) in a mature wheat crop can equal that obtained from three cuts of grass. Ensiled mature whole crop wheat is however characterised by a lower digestibility and lower crude protein concentration than good quality grass silage. Addition of urea at ensiling has been shown to increase the digestibility and the non-protein nitrogen concentration of whole crop wheat silage. The objectives of this study were to determine (i) the effect of urea-treatment on the in vivo digestibility of wheat of relatively high moisture concentration and (ii) the effects of the provision of a rapidly fermentable carbohydrate supplement on nitrogen metabolism in steers fed these silages.