The trial was conducted to evaluate the effect of a by-product of solid state fermentation (Synergen™ (SGN), Alltech Inc, Nicholasville KY, USA) on broiler performance and health. One thousand two hundred and eighty male Ross 308 broilers were used in a 42 day pen trial. The trial was designed as a 2 × 2 factorial, with two diet specifications (standard and reformulated) plus or minus SGN (0 and 200 g/t, SGN replaced with commercial enzyme Ronozyme™ at 150 g/t) to give four dietary treatments in total in a corn-soy based diet formulated to commercial standards. Birds fed the reduced energy diets had significantly lower cumulative feed intakes at 42 d (P < 0.01) compared to those on the full specification standard diet. There were no significant differences in broiler body weight due to treatments at any age. Significant improvements (P < 0.05) in FCR, primarily due to SGN inclusion in the feed, were observed for all weekly reported data. There were no significant differences in either mortality or EPEF for any of the treatment diets. The present study indicates that SGN, a by-product of solid state fermentation (SSF) can improve feed conversion of broilers fed a corn-soy diet.