|Lellis, W. - USGS, WELLSBORO, PA|
Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 22, 2006
Publication Date: June 1, 2006
Citation: Barrows, F., Lellis, W.A. 2006. Effect of diet processing method and ingredient substitution on feed characteristics and survival of larval walleye (stizostedion vitreum) journal equivalent: journal of the world aquaculture society.. Journal of the World Aquaculture Society. 37(2):154-160. Interpretive Summary: Diets for fish larvae are the limiting factor for production of a wide variety of species. We developed and evaluated two methods for the production of larval feeds. Methods for producing larval feeds that can be done in the laboratory, but are scalable to production operations, is needed so researchers can evaluate new formulations and determine nutrient requirements for this delicate life stage. Both the PARA and the MEM diets fit these production criteria, but feeding diets produced by the PARA method resulted in higher survival of fish larvae. The PARA method provides researchers, and industry a method to produce larval feeds of appropriate size, and other physical characteristics.
Technical Abstract: Two methods were developed for the production of feeds in the sizes needed to replace live Artemia nauplii (250-400 um) and rotifers (<250 um) in larval fish culture. The micro-extrusion marumerization (MEM) method produces particles that are palatable and water stable. A wet mash of ingredients is extruded through a 500 um screen in a radial discharge extruder to produce long noodles. The noodles are then fractured, shaped, smoothed, and densified in a marumerizer. The particle-assisted rotational agglomeration (PARA), does not require an extruder and produces high yields of particles less than 250 um in diameter. A wet mash is placed directly in the marumerizer and rotated with inert beads to form, shape, and densify the particles. Feeds produced with the PARA method have lower density than feeds produced by MEM. Each method was used to produce feeds in the 250-400 um and 400-700 um range and compared with a commercial diet for feeding larval walleye in two experiments. In the first experiment, 30-d survival was greater (P < 0.05) for fish fed a diet produced by PARA (49.1.0%) than by MEM (27.6%) or the commercial formulation (24.4%). In the second experiment, 23-d survival was equal among fish fed either a PARA (48.4%) or commercial diet (46.5%), but lower (P < 0.01) for fish fed an MEM diet (19.6%). Inclusion of 4% freeze-dried Artemia improved (P < 0.04) survival of fish fed MEM particles, but not those fed PARA particles. Fish fed Fry Feed Kyowa had greater (P < 0.05) weight gain than fish fed other diets in both experiments. Data indicate that the PARA method of feed processing produces smaller, lower-density particles than the MEM process, and that feeds produced by the PARA process support higher survival of larval walleye with low capital and operating costs.