Evaluation of Open‐Formula Grower Diets for Juvenile Walleyes

Abstract

AbstractTwo feeding trials (72 and 91 d) with replicated treatments were conducted to evaluate four experimental open‐formula diets for juvenile walleyes Sander vitreus. The four diets were similar in crude protein (45.3–48.5%) and energy (1,149–1,175 J/g) but differed in the type of oil used (menhaden, flaxseed, soy, and commercial microalgae oil [CMP] with a high omega‐3 fatty acid content). The fat content of the four diets ranged from 12.9% to 14.4%, compared with 16.8% for a commercially manufactured walleye grower diet (WG). A conditioning diet (10.3% fat) was fed all fish before the start of and during the first feeding trial. Six diets (WG, conditioning, menhaden, flaxseed, soy, and CMP) were fed in the first trial and the four experimental diets in the second feeding trial. Differences in final weight, relative growth, and specific growth rate among the treatments were not significant in either feeding trial. The similarity in growth in view of the differences in diet composition indicates that there is flexibility as to the choice of lipids with which to formulate diets for juvenile walleyes. The type of oil, however, had a major influence on total ingredient cost; soy oil was more economical than menhaden oil, but the formulation with CMP oil was twice as much as that with soy oil and 1.8 times as much as that with menhaden oil. This study validates prior reports that indicate highly specialized diet formulations are not required for juvenile walleyes.