Use of dried distillers grains and nitrogen sources in high forage diets

Dried distillers grains (DDG) are increasing in availability and have nutrient profiles which benefit high forage diets. Their use may increase production on a fixed land base by increasing animal performance and/or reducing forage intake. Approximately 40% of their nutrient composition consists of protein and lipid. Determination of effects of DDG, as well as protein, and lipid fractions of DDG may provide useful information to producers wishing to use DDG. Levels of DDG or supplements designed to represent protein or lipid fractions of DDG were fed to 120 heifers. Supplementation of DDG increased animal growth and reduced forage intake. The protein supplement increased animal growth 39% as much as DDG and reduced forage intake similar to DDG while the lipid supplement had no effect on animal growth or forage intake. The response of DDG on animal growth is likely due to providing a combination of lipid and protein. The protein fraction of DDG is also relatively high in methionine, which is the first limiting amino acid in forage diets. To determine if a portion of the response to DDG is from methionine, 60 heifers were fed levels of DDG or methionine. Supplementation of DDG increased animal growth and reduced forage intake whereas methionine reduced animal growth when fed at high levels. Methionine in DDG is not solely responsible for a portion of the improvement in animal growth. An additional trial designed to determine providing specific amino acids improves growth suggests providing a variety of amino acids increases growth whereas providing a single amino acid may not. Society is increasingly concerned about ammonia volatilization and ruminants grazing actively growing forages may contribute to ammonia emissions. Protein, carbohydrate, lipid, or a combination of lipid and protein were fed to 60 heifers grazing smooth bromegrass pastures and to steers fed alfalfa hay to determine if nitrogen capture can be improved by supplementation of these nutrients. Carbohydrate supplementation was expected to improved nitrogen capture due to increased microbial growth in the rumen, but no increase was observed. Supplementation of protein and lipid increased nitrogen retention suggesting feeds such as DDG may reduce ammonia losses.