As a result of increasing demand, uncertain availability, and increasing cost for fish meal (FM), fish nutritionists have been driven to find alternative sources of protein. Particularly for carnivorous species such as Yellow Perch (Perca flavescens (Mitchell), alternative plant-based feedstuffs have shown decreased performance compared to FM. Processed (mechanical, chemical, or microbiological) soybean products are of primary interest as alternative feedstuffs due to their availability, domestic production, low price and nutritional profile; however, use of processed soy has displayed varying degrees of success. Novel soy ingredients created through bioprocessing technology potentially provide more highly digestible nutrients with fewer anti-nutritional factors (ANFs) than traditionally processed soy products.
To examine the utility of certain bioprocessing technologies, ingredient compositions were compared and incorporated into three Yellow Perch feeding trials. The first feeding trial was completed to measure apparent digestibility of protein and energy of commercial and experimental bioprocessed soybean meal (BP-SBM), and other common feed protein ingredients. Bioprocessing consistently upgraded the bioavailability of protein in defatted soybean meal, while commercially bioprocessed xvi Hamlet HP 300 provided the highest digestibility of all soy products tested. Extrusion as a pretreatment to bioprocessing had a negative effect on digestibility.
The second experiment was a 14-week feeding trial to evaluate growth performance, digestibility, and organosomatic responses of Yellow Perch fed diets containing commercial alcohol-washed soy protein concentrate (SPC), bioprocessed soy white flake (BP-WF), or extrusion pretreated BP-WF as complete FM replacements. Each soy protein source was replicated in diets with and without supplemental lysine + methionine. BP diets consistently performed better than SPC diets. Extrusion pretreatment led to improved consumption and growth performance over unextruded products. Lysine and methionine supplementation further improved growth. SPC diets provided the best feed conversion ratio (1.62) and highest apparent digestibility of protein (91.8%), but examination of anatomical characteristics revealed significant deficiencies in fish fed SPC diets.
In the final 16-week feeding trial they evaluated growth performance, feed intake, and organosomatic responses of Yellow Perch fed diets containing various processed SBM products. Treatment factors included soybean variety (GMO or non-GMO), extrusion pretreatment and FM replacement levels (40 and 70%). An FM control and 14 soy-based diets were formulated on a dry matter basis to contain similar crude protein (45%), lipid (9%), and gross energy (20.9 MJ/Kg). Five soy treatments displayed higher relative growth than the FM control diet and nine lower growth. A non-GMO, nonextruded, extruded SBM provided enhanced growth at both inclusion levels when compared to FM. Both the GMO and non-GMO commercial SBMs provided similar growth to the reference diet at the low FM replacement level, but growth was depressed at the higher level.