INFLUENCE OF DIETARY-FAT LEVEL ON FEED-INTAKE, GROWTH AND FAT DEPOSITION IN THE WHITEFISH COREGONUS-LAVARETUS

Whitefish, Coregonus lavaretus, of initial mean weight 260-265 g were fed either a high-fat or a low-fat diet (dietary fat: 27.5% vs. 12.6%) to examine the influence of dietary fat level on feed intake, growth and patterns of fat deposition. The fish were held at 14.5 degrees C u nder a 24L:0D photoperiod, and were fed for 4 h each day. The experime nt was run for 11 weeks during which feed intake (three times by X-rad iography) and growth were monitored. Samples of fish were taken for bo dy composition analysis at the start and end of the experiment. There were only small differences between dietary treatment groups in feed i ntake and final body weights, but the body composition of the fish was significantly influenced by the fat content of the diet. The whitefis h fed the high-fat diet tended to have higher relative fat contents in the viscera [% fat as mean (SD): 29.6 (9.4)% vs. 22.1 (10.0)%] and ca rcass [% fat: 12.7 (1.9)% vs. 10.5 (1.3)%] than their counterparts fed the low-fat diet. This resulted in a higher whole-body fat concentrat ion [% fat: 14.0 (1.9)% vs. 11.5 (1.5)%] amongst the fish fed the high -fat diet, and these fish had a higher energy gain than the whitefish fed the low-fat diet. The results confirm that it is possible to manip ulate the chemical composition of whitefish by changing dietary compos ition.