Date of Award
Master of Science
Many sources of protein have been investigated to reduce the use of fish meal (FM) in aquaculture feeds, including soybean meal (SBM). However, FM replacement in feeds for carnivorous species is limited by problems with feed intake, growth rate, and overall health associated with reduced digestibility and anti-nutritional factors found in SBM. However, soy processing strategies can reduce the effects of anti-nutritional factors and improve utilization. Therefore, we examined the possibility of further FM replacement in SBM maximized feeds for hybrid striped bass using refined soy products, soy protein concentrate (SPC) and soy protein isolate (SPI). Results indicate that further FM sparing is possible, beyond what can be achieved with SBM. For example, it is possible to reduce dietary FM content as low as 5% using SPC, and though this negatively affects growth rate, this effect may be reversed by the addition of a betaine-based attractant. Replacement with SPI resulted in such a degree of feeding reluctance that starvation and cannibalization became issues during the trial. Reducing FM content below 5-10% resulted in more variable production performance and, when using SPI, increased incidence of cannibalism. No differences in stress tolerance were observed during the trials; however, there was a trend of increasing handling mortality in fish fed the SPC diets. Refined soy proteins can be used in conjunction with SBM to spare FM, but the cost of these products, along with their acceptability to aquatic livestock, will determine the extent of their utilization in aquafeeds.
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