Bioavailability of niacin from feed ingredients commonly used in feeds for channel catfish, Ictalurus punctatus

Abstract

A catfish bioassay for available niacin was developed using liver NAD levels as the response measure. Triplicate groups of fingerling channel catfish were fed 7 different feed ingredients as the sole source of dietary niacin in a basal casein–gelatin diet for 8 weeks. Three other experimental diets containing known amounts of supplemental niacin (6, 9 and 12 mg/kg diet, respectively) were also fed to triplicate groups of fish to establish the levels of NAD in the liver after 8 weeks. A standard linear regression equation of available niacin in diet ( y in mg/kg) as a function of liver NAD concentration ( x in μmol/g) was derived and used to determine the amount of available niacin in the feed ingredients. Menhaden fish meal (MFM), meat and bone/blood meal (MBM), wheat middlings (WML), cooked corn (CCO), uncooked corn (UCO), cottonseed meal (CSM) and soybean meal (SBM) contained 105.3, 50.5, 153.3, 21.9, 12.8, 22.5 and 20.3 mg/kg of available niacin, respectively. When compared to the total niacin content of each feed ingredient, niacin in animal tissue (MFM, MBM) was totally available to channel catfish. Availability of niacin in cereals and cereal byproducts, WML, CCO and UCO, was about 60, 44 and 28%, respectively. Niacin availability in the two oilseeds, CSM and SBM, was found to be 58 and 57%, respectively. Niacin availability from corn was increased by about 57% when the corn was extrusion-cooked. It was concluded that supplementation of niacin may not be needed or can be lowered in typical commercial catfish feeds because of the relatively high amount of available niacin found in the feed ingredients.