Application of enzymes in an effort to improve nutrient digestibility of plant-based feed ingredients for swine and poultry has been studied for decades. Essentially, an enzyme(s) must match the target substrate(s) in a feedstuff which have been shown to have a negative impact on nutrient digestibility or voluntary feed intake. As such, there may need to be a ‘cocktail’ of enzymes to effectively breakdown the complex matrixes of fibrous carbohydrate structures. With the inverse relationship between fiber content and energy digestibility being well described for several feed ingredients, it is only logical that development of enzymes that degrade fiber, and thereby improve energy digestibility or voluntary feed intake, will have a chance to be beneficial, both metabolically and economically. The current experiment involved the evaluation of 10 commercially available feed additives (enzymes, yeast, and probiotics) in nursery and finisher pigs fed diets containing 30% DDGS, each over a 5 week period. Efficacy was based upon apparent total tract nutrient digestibility (as measured indirectly using dietary markers) and pig performance. Overall, the results of the current experiment suggest that commercially available enzyme/additive products have variable (both positive and/or negative) effects on nutrient digestibility coefficients, but none of these products were effective in improving starter or finishing pig growth performance when fed nutritionally adequate corn-soy diets containing 30% DDGS. For further information, contact Dr. Brian Kerr, USDA-ARS-NLAE, Ames, IA, by phone (515-294-0224) or email ([email protected]).