An earlier study conducted at the Centre for Dairy Research (Phipps et al. 1996) using a total mixed ration (TMR) based on maize silage, showed that when distillers grains wheat and molassed sugar beet feed (MSBF) replaced cereal and protein supplements, milk yield and dry matter (DM) intake were maintained but there was a large and significant reduction in milk fat and a small but significant reduction in milk protein. This depression in milk protein was attributed to the high oil content of distillers grains, which would have reduced fermentable metabolisable energy intake which in turn may have adversely affected microbial protein synthesis and reduced milk protein content. The aim of the current study was to devise a nutritional regime using distillers grains maize (DGM) and MSBF in a TMR which would allow milk fat content to be substantially reduced without compromising either DM intake, milk yield or milk protein content.