Extrusion Temperature and Pellet Size Interact to Influence Growth Performance of Hybrid Striped Bass Fed Industrially Compounded Aquafeeds

Abstract The objective of this experiment was to jointly assess the possible influences of aquafeed extrusion temperature and pellet size and uniformity on growth performance of juvenile hybrid Striped Bass (White Bass Morone chrysops × Striped Bass M. saxatilis). A diet formulated to meet or exceed the nutritional requirements of hybrid Striped Bass was coupled with different feed manufacturing strategies to yield a range of compositionally identical but physically distinct feeds. Batches of feed were extruded at 107 ± 6°C or 127 ± 3°C through dies estimated to yield pellets that were “small” (3 mm), “recommended” (4 mm), or “large” (5 mm) relative to the size ranges suggested for the target fish size. Portions of the uniformly small and large feeds were combined (25:75, 50:50, and 75:25 ratios of small : large pellets) to create additional mixed-sized feeds. Fish were stocked in a recirculating aquaculture system (fish size: 19.6 ± 0.7 g [mean ± SE]; 10 fish/tank) comprising thirty-six 119-L circular tanks, mechanical and biological filtration units, and a supplemental aeration system. Feeds were randomly assigned to triplicate tanks of fish (N = 3), and fish were fed to apparent satiation once daily for 8 weeks. Results indicated that extrusion temperature and, to a lesser extent, pellet size and uniformity affect the practical feeding value of hybrid Striped Bass feed. Although the effects were observed to be interactive and somewhat variable, there appears to be value in extruding the formulation tested at higher temperatures and producing uniform pellets of a size somewhat larger than is typically recommended for phase II hybrid Striped Bass.