NPY FAMILY GENES RESPOND NEGATIVELY TO ALTERNATIVE FEEDSTUFFS IN CHANNEL CATFISH DIETS      

Of considerable importance in fish nutrition is the development of aquafeeds using alternative dietary ingredients which will allow aquaculture to grow globally, without putting excessive pressure on natural fisheries or adding considerable cost, while also addressing and maintaining the important human health benefits desired by consumers of aquaculture food products.  Although the focus appears to be on reducing costs for carnivorous fish species, there is a pressing need to reduce production costs for omnivorous species as well.  For a species such as the Channel Catfish, profit margins can be small and even slight increases in fish feed costs can have a huge impact on producers.  Not only have fishmeal prices increased dramatically over the past couple decades, but the price of soybean meal has also increased, enough so that catfish producers are requesting lower-cost feeds and alternative feeding strategies.

Historically, nutritional studies have focused on meeting nutrient requirements and substituting less expensive protein feedstuffs for fishmeal, then evaluating the effects on fish performance.  While there remains inherent value in these types of studies, there is a need to look more closely at the physiological and metabolic effects of alternative dietary protein sources.  More recently, studies have evaluated individual genes or entire transcriptomes, each approach having significant value as well as inherent complications.  In the present study, three alternative dietary formulations for Channel Catfish were evaluated and compared to a high quality control diet.  The expression of 44 genes in 4 tissue groups associated with appetite, growth, metabolism, and gut health were determined after a 12 week feeding trial.

At the conclusion of the study, growth was unaffected; however, each of the alternative dietary formulations resulted in higher FCR (P≤0.05).  Associated with this were decreases in neuropeptide Y (NPY) family genes, specifically hypothalamic NPY and intestinal peptide YY (PYY) (Fig 1).  Interpretation of these results led to the conclusion that increased feed consumption, resulting in higher FCR, is occurring through hypothalamic NPY suppression.  PYY's role is less clear, and may be as a modulator of intestinal transit rate.