The efficiency of use of feed protein for milk protein production is very poor, particularly for animals offered conserved forages. Contributing to this is the inefficient capture of rumen degradable N in situations where a readily fermentable energy supply is not available for use by the rumen microbial population. The incorporation of a whole crop cereal into a conserved forage could increase rumen protein efficiency. This experiment was carried out to investigate the milk production of dairy cows offered a conserved forage of a whole crop barley and kale bicrop compared with grass silage, and a mixture of the two.