The incorporation of PepSoyGen (PSG), a commercially produced fermented soybean meal product, was evaluated in a 205‐d feeding trial. Three isonitrogenous and isocaloric experimental diets containing 0, 35, or 50% PSG and 40, 15, and 0% fish meal, respectively, were fed to Rainbow Trout Oncorhynchus mykiss. The diets containing either 0% or 35% PSG produced similar total tank weight gains, percent gains, and feed conversion ratios and were significantly different from the diets containing 50% PSG at the end of the trial. Mean individual fish lengths and weights were significantly greater in the fish receiving 35% PSG than either of the other two diets. Specific growth rate (SGR) was significantly lower in the 50% PSG treatment, but there was no significant difference in SGR between the other two diets. Viscerosomatic index was significantly lower in the fish fed 35% PSG. Hepatosomatic index was not significantly different among the diets, but fish receiving 50% PSG had a significantly poorer liver condition scores. No other significant differences were observed in health assessments of fat, fin condition, gills, pseudobranchs, opercles, eyes, guts, kidneys, or spleens. Significant differences were observed in distal intestine morphology among the diets at day 94, but no differences were observed at the end of the trial on day 205. Splenosomatic index, macrophage activity, and respiratory burst activity were not significantly different among the dietary treatments. Based on these results, PSG can safely constitute 35% of Rainbow Trout diets without any decrease in rearing performance compared with a reference blend containing fish meal.

Off-flavor in catfish restricts farm marketings 10 to 45% depending on the season. The economic impact on society of this imposed supply restriction depends, in part, on the elasticity of demand for catfish. Econometric estimates based on disaggregated processing plant data indicate an elastic demand at the processor level but an inelastic demand at the farm level. Short-run social welfare gains from the elimination of off-flavor are estimated to equal 12.0% of farm revenues ($10.0 million in 1983). The inelastic demand for catfish at the farm level, however, means that most of the societal gains will accrue to individuals beyond the farm gate. Thus, an economic justification exists for public sector funding of off-flavor research.

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Marine-derived fish meal (FM) is a traditional component of commercial aquaculture feeds for many farmed fish species. Modern bioprocessing technologies have been developed to produce high-protein plant-based ingredients for aquafeeds to further reduce FM and other conventional animal protein sources. A 90-day feeding trial using juvenile rainbow trout (Oncorhynchus mykiss) (27.9 ± 1.4 g; mean ± SE) was completed to evaluate growth, feed efficiency, general health and immunological responses to diets containing experimental plant-based protein sources and reduced FM. Trout were fed one of four dietary treatments: experimental bioprocessed soy protein concentrate (BSPC), commercially available enzymatically hydrolysed soy protein concentrate (CSPC), experimental bioprocessed barley protein concentrate (BBPC) and a FM control (FMC). At trial termination, there were no significant differences in relative growth (RG) or specific growth rate (SGR) between fish fed either FMC or BSPC (p > .05). Fish fed either CSPC or BBPC resulted in significantly lower RG and SGR than the FMC (p < .05). Significant respiratory burst analysis differences were observed among treatments at day 90 (p < .01), for fish fed either FMC or CSPC diets. This assessment of bioprocessed plant-based protein ingredients facilitates the characterization and incorporation of bioprocessed soy and barley protein as the industry continues to evaluate FM replacements in rainbow trout feeds. K E Y W O R D Salternative feed ingredients, fishmeal replacement, innate immunity, nutritional physiology, rainbow trout, soy fermentation 1

A risk programming method that evaluates production plans based on expected income and risk was demonstrated using representative data from Panama. Results illustrate the usefulness of the program in presenting production choices to decision makers and evaluating those choices under changing conditions. Less experienced or less financially secure farmers may select farm plans that differ quite importantly from those chosen by more experienced or more financially secure farmers. If farm survival is in doubt, more conservative farm plans will generally be adopted. Without consideration of the potential losses, it will often appear that all farmers should pursue the most intensive farm plan within their farming capabilities. However, many farmers will employ less intensive management strategies if the potential for losses associated with more intensive strategies is perceived to be excessive. The model indicated that management strategies were sensitive to changes in shrimp price and feed cost, but less sensitive to the costs of post larvae or energy. Also, shrimp farm managers should give serious consideration to not producing in the dry season due to relatively high risk and low expected returns. Farmers should be most concerned with quality and availability of post larvae, not price. If hatcheries can address these concerns, the higher price of hatchery post larvae will be justified.