Soy protein concentrate in diets for Atlantic halibut (Hippoglossus hippoglossus)

Four experimental diets were fed to triplicate groups of Atlantic halibut in a 2 X 2 factorial design, testing the effects of protein source and the use of an attractant. The diets contained 61% fish meal (FM) or 37% FM and 28% soy protein concentrate (SPC) with or without a coating of squid meal. In the SPC diets, 44% of nitrogen was supplied from the SPC. The mean initial fish weight was 633 g, and at the end of the 12-week trial, the mean fish weight was 874 g. There was no significant effect of dietary treatment on specific growth rate (0.43 +/- 0.02% body weight d(-1), mean +/- S.E.M.). Feed efficiency ratio was significantly lower in the group fed the SPC diet (1.22 +/- 0.02) compared with those fed the FM diet (1.28 +/- 0.02), Fish fed the SPC diets had a higher feed intake (0.64 +/- 0.02%) than those fed the FM diet (0.59 +/- 0.02%). Addition of squid had no effect on feed intake. The groups fed diets not supplemented with squid were used for determination of whole body chemical composition, and the remaining fish from these groups were subsequently stripped for feces for digestibility estimations, There were no effects of protein source on digestibility or protein or energy retention in whole fish. The fish fed the diet containing soy protein had a slightly higher dry matter (DM) content (P < 0.05), than the fish fed the diet containing only fish meal. (C) 1999 Elsevier Science B.V. All rights reserved.