Brewers Grains (BG) are the solid residue left after the processing of cereal grains to produce beer. Due to poor digestibility in monogastric animals like fish BG are primarily fed to ruminant livestock . Inclusion rates of BG in diets for fish rarely exceed 30% of the formulation due to poor utilization. AllzymeTM is a proprietary digestive enzyme complex containing live bacteria cultures to aid in gastric fermentation of poorly digestible feedstuffs which may improve utilization of BG in diets for fish .
A feeding trial was conducted to evaluate the effects of adding AllzymeTM to diets containing increasing levels of BG in diets fed to Nile tilapia ( Oreochromis niloticus ). Twenty juvenile tilapia (average weight 5.0 g) were stocked into each of thirty- six 76 L aquaria with four aquaria per dietary treatment. Fish were fed three times daily one of nine randomly assigned experimental diets with basal formulations containing either 0% BG, 27% BG or 54% BG and with AllzymeTM added at either the manufacturers recommended rate (MRR) or at two times the MRR to each basal diet . The 0% BG diet served as a control and was formulated after a traditional commercial tilapia diet. All diets contained 8% fish meal and were formulated to be isocaloric and isonitrogenous. Added BG replaced conventional soybean meal and wheat flour in the formulations.
Water quality variables remained acceptable for tilapia production throughout the trial. Feed acceptance and overall growth was good for all diets with an average of >800% weight gain in six weeks. There was no significant difference (P>0.05) in survival or FCR among treatments which averaged 90% and 1.4 overall, respectively. The average weight (g) and SGR of fish fed the control diet 0% BG (54.1 and 1.1, respectively) was statistically greater than for fish fed the 27% BG diet without enzyme addition (46.4 and 0.93, respectively) and for fish fed all the 54% BG diets which averaged 44.2 g and SGR of 0.88 overall. The 27% BG diets containing added AllzymeTM achieved similar growth performance as the control diet.
Statistically, a ddition of AllzymeTM did not significantly improve fish performance over the performance of the basal formulations; however, the trend was a slight increase in growth performance of fish when AllzymeTM was added at the MRR, which did not increase further when the inclusion rate was doubled. Addition of AllzymeTM may provide a growth benefit to feed formulations which include alternative low nutrient density feed ingredients such as BG; however, under the conditions of this study the magnitude of the benefit was slight. To further evaluate the potential benefit of adding AllzymeTM in diets for fish; additional studies should evaluate different species and longer durations of feeding.