Feasibility of superworm, Zophobas morio , meal as a partial fishmeal replacer in fingerling rainbow trout, Oncorhynchus mykiss , diet: growth performance, amino acid profile, proteolytic enzymes activity and pigmentation

Abstract

To characterize the effects of a defatted superworm meal (SWM) on the zootechnical performance and nutrient utilization of fingerling rainbow trout, we provided five practical diets with 0 (control), 10, 20, 30 and 40% SWM to substitute fishmeal. Fingerlings (N = 225; 9.9 ± 0.5 g) were randomly allocated over five treatments in triplicate. After eight weeks, the replacement of fishmeal with SWM up to 110 g/kg did not induce significant variations in the final weight and weight gain rate compared to the control group, while dietary 220 g/kg SWM had negative impacts on the growth and feed utilization attributes. The contents of protein and methionine were significantly reduced in the whole body with incremental dietary SWM. The pepsin and chymotrypsin activities were not influenced in the groups, but the lowest trypsin activity was seen in 40% replacement by SWM (p < .05). Total carotenoid content and redness of the fillet were improved with dietary SWM. No variation was seen in the digestibility of protein and dry matter in diets including 55 g/kg and 110 g/kg SWM compared to the control group (p > .05). Overall, optimum fishmeal replacement by SWM ranged from 162.6 to 184.2 g/kg in rainbow trout diet based on the broken-line regression model.