A Michigan StateUniversity analysis shows that a more-fermentable diet reduces fat-corrected milk yield of cows fed corn distillers grains. The analysis showed that forage type, grain concentration and grain fermentability — three factors that affect how fermentable the diet is — influenced a cow’s production response to corn distillers in the ration.  

For example, in the chart below, fat-corrected milk response to corn distillers grains was greatest for alfalfa, lowest for corn silage, and intermediate for a mixture of the two forages.