Effects of replacing fish meal with a combination of corn protein concentrate and meat meal on growth performance, biochemical profile, digestive enzyme activity, antioxidant activity, immune response, and economical efficiency in juvenile black rock

This study evaluated the effects of substituting fish meal (FM) with a 1:2 blend of corn protein concentrate and meat meal (CCM) on growth performance, digestive enzyme activity, biochemical composition, antioxidant and immune responses, and economic efficiency in juvenile black rockfish (Sebastes schlegelii). Seven experimental diets were prepared: a control diet containing 65 % FM and six test diets with 10 %, 20 %, 30 %, 40 %, 50 %, and 60 % of FM from the control diet progressively replaced with CCM. Juvenile rockfish (initial body weight: 3.6 ± 0.01 g) were randomly assigned to triplicate groups of 30 each and fed the experimental diet for 8 weeks. Growth parameters, including final body weight, weight gain, specific growth rate, feed efficiency, and protein efficiency ratio, significantly declined when FM replacement exceeded 40 %. Trypsin and lipase activity showed a linear decline with increasing CCM levels. Whole-body moisture content significantly increased, whereas crude protein content significantly decreased at 60 % FM replacement with CCM. Antioxidant enzyme activity and immune response markers declined at ≥ 50 % FM replacement. Although feed costs decreased with increasing CCM levels, economic conversion and profit indices were maximized at 40 % FM replacement. Broken-line regression analysis estimated the optimal FM-replacement level with CCM at 34.07 %. Overall, these findings suggest that up to 40 % of FM can be replaced with CCM in juvenile S. schlegelii diets without impairing growth, nutrient utilization, antioxidant function, or immune response, making it a cost-effective and sustainable alternative for aquafeeds.