Digestibility of corn distiller's dried grains with solubles in practical feeds with phytase and xylanase treatment fed to Nile tilapia

Abstract Distiller's dried grains with solubles (DDGS), a byproduct of ethanol production from cereal grains, has seen limited use by fish feed manufacturers as an alternative protein source. Over the past 20 years, advances and greater uniformity in processing methods have improved the quality of DDGS, and likely, its digestibility by fish. Our objective was to reevaluate the digestibility of corn DDGS by Nile tilapia using a present‐day commercial product. Apparent digestibility coefficients (ADC) for the major proximate nutrients (dry matter, crude protein, crude fat, ash, digestible energy, and phosphorus) were determined using a practical, commercial‐type feed that was formulated and processed with DDGS supplied at 30% as w:w substitution (DDGS diet) of the reference diet (Ref). After drying, Ref and DDGS diets were top‐coated with phytase (3310 FTU/kg) + xylanase (7665 BXU/kg) enzymes (Ref+ and DDGS+) and compared to their untreated dietary counterparts. Digestibility of crude protein was similar among diets and unaffected by enzyme treatment. For dry matter and digestible energy, ADC values were significantly lower for the DDGS diet, but enzyme addition improved digestibility to that of the Ref diets. Apparent digestibility for crude fat and ash was significantly better for the DDGS feed with ash digestibility improved after treatment with xylanase + phytase for both Ref+ and DDGS+. For phosphorus, digestibility was similar among the Ref, Ref+, and DDGS diets, but with enzyme treatment, the phosphorus ADC increased significantly in DDGS+. Results of this digestibility trial show that corn DDGS is a highly digestible protein source for use in feeds of Nile tilapia at 30% of diet. Generally, apparent digestibility of proximate nutrients was either better or similar in DDGS when compared to the reference diet and could be further improved with addition of xylanase + phytase.