A:   I don't think that feeding distillers grains has much of an influence on frame size in feedlot cattle. Phenotype (the attributes of an animal that you can see) is a funtion of their genetic make-up (genotype) + enviroment. The heritability of yearling frame size is 50%, so this trait would be considered moderate to highly heritable. With this high of heritablility, it would be fairly easy to increase frame size in cattle. The environment component of phenotype would include managment and how the animals are handled. Now I would agree that distillers grains are high in protein and when priced competitively, they may be included in feedlot diets as high as 30 to 40% of the diet on a dry matter basis, and in some situations, protein could be over-fed. In addition, about 65% of the protein in distillers is by-pass protein (UIP) that is brokendown in the small intestine and absorbed as amino acids and used by rthe animal. Excess protein will enter the liver and a portion of that will be converted to urea and enter back into the rumen through saliva and the rumen bugs will use this to make their own protein. I think a large portion of any other excess protein will be used as energy by the animal. So I don't think feeding distillers grain in feelot diets will have much of an impact on long-bone growth in cattle. Our data would suggest that when distillers grains are included in a feedlot diet that cattle will reach a marbling end-point sooner than calves fed a corn-based diet because that distillers fed calves have a greater ADG.

So, feedlot diets are very seldom, if ever, protein deficient whether feeding distillers or not. The increase in frame that you think you are observing is more of a function of genetic make-up than feed ingredient.