MULTIVARIATE EVALUATION OF FEED FOR ATLANTIC HALIBUT

The present investigation tested three physical properties of fish fee d: dry matter content, floating vs. sinking feed, pellet size and thei r cross-terms upon growth and feed utilization of Atlantic halibut (Hi ppoglossus hippoglossus) in the ongrowing phase. A factorial design (F D, 2(3)) with four center points was applied. Each of three size subgr oups within each rearing tank were modeled across 12 tanks. Nine singl e growth and feed utilization responses and three combined responses ( super Y's) were modeled with the aid of PLS (partial least squares reg ression). The fish were individually tagged and reared for three month s at a mean temperature of 8.7 degrees C. The models of growth and fee d utilization were improved by sorting the individual fish, according to blindness, and by splitting the modeling in size and time groups. T he application of weighted multiresponse models gave more relevant inf ormation than single response models. High dry matter content (dry fee d) caused the most unambiguous and positive effect on growth and feed utilization. The floating property of the feed was negatively correlat ed to growth rates, especially for small fish. The pellet size of 8-9 mm was too big for the small fish (< 55 g at start of the experiment). Relatively small pellets should only be used if they are sinking. Lar ge pellets resulted in the highest conversion of feed into flesh, espe cially by the big fish. Pellet size (var. No. 3) and the combined effe ct from pellet size and high dry matter content (var. Nos. 1 x 3) were the most significant positive parameters upon GFCE (gross feed conver sion efficiency) and protein utilization. High dry matter content (var . No. 1) and the combined effect from pellet size and high dry matter content (var. Nos. 1 X 3) were most important to fat utilization. The sinking/dry/large pellets showed the highest super Y response. Future feeds should consequently maximize these parameters within biological reasonable limits to achieve the best utilization of the feed.