Digestibility of Conventional and Novel Dietary Lipids in Channel Catfish Ictalurus punctatus

SIMPLE SUMMARY: The digestibility of ingredients in fish diets must be known to use the least-cost feed formulation. However, there is very little published information on lipid (fat) digestibility in fish. With this information, commercial feed producers can choose lipids based on high utilization by the fish, as well as cost. We conducted a feeding trial with catfish fed diets with different lipids: soybean oil, soybean oil with conjugated linoleic acids, catfish offal oil, flaxseed oil, menhaden fish oil and poultry fat. After feeding, fish feces were collected for nutrient analysis and compared to the lipid content of the diets. Lipid and fatty acid digestibility were high overall for all of the lipids tested. However, the digestibility of certain fatty acids was different from overall lipid digestibility. This information can be used to choose the best lipids to meet catfish needs, enhance healthy fats in the fish for human consumers, and produce a cost-effective feed. ABSTRACT: Lipid and fatty acid digestibility is presumably high in Channel Catfish, but data is lacking. We determined the lipid and fatty acid digestibility of traditional and alternative dietary lipids in Channel Catfish to inform lipid choice for commercial diets. Six diets contained 4% of different lipids: soybean oil (SBO), soybean oil containing conjugated linoleic acids (CLA-SBO), catfish offal oil (COO), flaxseed oil (FXO), menhaden fish oil (MFO) and poultry fat (PF). Diets were fed to Channel Catfish (150–200 g) maintained at 26.5 °C in each of six 110 L aquaria. Six hours post-prandial, feces were collected for analysis. Total lipid, crude protein and fatty acids of lyophilized feces were analyzed, and apparent digestibility coefficients (ADCs) were calculated. ADCs of lipid, saturated and monounsaturated fatty acids, linoleic acid and protein digestibility were similar among diets. CLA isomers (cis-9, trans-11 (84.1%) and trans-10, cis-12 (90%)) in the CLA-SBO diet were highly digestible. Oleic acid digestibility was highest in the PF diet. ADC was high for α-linolenic acid in the FXO diet, and for arachidonic acid and n-3 LC-PUFA in the MFO diet. Overall, total lipid digestibility was high, but ADCs of individual fatty acids differed by source.