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Abstract
A study was conducted to evaluate three practical lipids -catfish oil, menhaden oil, and tallow -as energy supplements for channel catfish fed extruded diets during a two-year production trial. For 20 months, pond-raised catfish were fed a custom-manufactured diet containing 2% or 4% of each lipid source. Fish were sampled after eight months of treatment at approximately 0.5 kg body weight (year-1 fish) and again at termination of the experiment (20 months) at approximately 1 kg body weight (year-2 fish) to determine effects of lipid supplementation on weight gain, tissue total lipid content, and dressing percentage. Fish production among the six treatment groups also was compared. Survival, per-hectare yield, live weight at harvest, dressing percentage, and liver lipid content did not differ (P> 0.05) among year-1 fish or year-2 fish, regardless of dietary treatment. Similarly, muscle (fillet) lipid content of year-1 fish did not differ (P> 0.05) among treatments, nor did muscle lipid levels in year-2 fish, with one exception: year-2 fish fed 2% catfish oil had significantly higher muscle lipid levels than fish fed 4% catfish oil. The reason for this difference was not apparent. When data were pooled by year without regard to diet, year-2 fish had significantly lower hepatosomatic index and visceral fat content and significantly higher dressing percentage and muscle lipid content than year-1 fish. Results indicated no difference among catfish oil, menhaden oil, and tallow as dietary energy sources for channel catfish raised in ponds from fingerling size to 1-kg body weight.
