Multivariate evaluation of feed for Atlantic halibut

The present investigation tested three physical properties of fish feed: dry matter content, floating vs. sinking feed, pellet size and their cross-terms upon growth and feed utilization of Atlantic halibut (Hippoglossus hippoglossus) in the ongrowing phase. A factorial design (FD, 23) with four center points was applied. Each of three size subgroups within each rearing tank were modeled across 12 tanks. Nine single growth and feed utilization responses and three combined responses (super Yʹs) were modeled with the aid of PLS (partial least squares regression). The fish were individually tagged and reared for three months at a mean temperature of 8.7°C. dels of growth and feed utilization were improved by sorting the individual fish, according to blindness, and by splitting the modeling in size and time groups. The application of weighted multiresponse models gave more relevant information than single response models. ry matter content (dry feed) caused the most unambiguous and positive effect on growth and feed utilization. The floating property of the feed was negatively correlated 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. Large pellets resulted in the highest conversion of feed into flesh, especially by the big fish. Pellet size (var. No. 3) and the combined effect from pellet size and high dry matter content (var. Nos. 1 × 3) were the most significant positive parameters upon GFCE (gross feed conversion 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 × 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.