Effects of dietary lipid source and concentration on channel catfish (Ictalurus punctatus) egg biochemical composition, egg and fry production, and egg and fry quality

We conducted a study to determine the effects of lipid source (poultry fat, PF or menhaden fish oil, FO) and concentration (4 or 10% lipid supplementation) in channel catfish broodstock diets on subsequent egg biochemical composition, egg production, and egg and fry quality. Three female and one male USDA-103 strain three-year-old broodfish were stocked into 16 3860-L outdoor tanks in January and randomly assigned one of the four diets (four replicates per diet). Fish were fed based on a water-temperature-dependant schedule. Spawning cans were added to tanks when water temperature reached 21 °C, and the cans were examined three times weekly for egg masses. Masses were enumerated, weighed, measured, analyzed for proximate and fatty acid composition, and incubated. Date to hatch, hatching success, fry growth and survival, and fingerling growth and survival were monitored. Supplementation of catfish broodstock diets with 10% fish oil increased spawning success, fecundity, total egg volume (matrix removed), individual egg weight, eggs·spawn⁻¹ (volumetric), total egg lipid concentration, hatching success, and fry survival compared to a control diet with 4% fish oil. The 10PF diet performed similarly to the 10FO diet in all measured parameters except egg fatty acid composition, although results for the 10PF diet did not always differ from those of the 4FO or 4PF diets. The 10FO diet produced significant decreases in egg saturates and MUFA, and increases in n-3 HUFAs and the ratio of n-3:n-6 fatty acids compared to all other diets. However, in fish fed the 10FO or 10PF diets the differences in egg fatty acid composition did not result in different rates of hatching success, fry survival, or fingerling production. Improved spawning performance of catfish fed 10%-lipid diets may be due partly to increased dietary energy relative to the 4%-lipid diets. Although the dietary n-3:n-6 fatty acid ratios of the 10PF (0.3) and 10FO (5.6) diets were quite different, similar concentrations of HUFAs such as DHA and AA were present in the eggs of fish fed either diet. This indicates that catfish can synthesize HUFAs from 18-carbon precursors and deposit the HUFAs in the egg, and that a variety of lipid sources may be suitable for use in catfish broodstock diets. Current methods of channel catfish egg and fry production using growout diets with 28-32% protein and 6-7% lipid are suboptimal based on the results of this study.