Gastrointestinal responses of rainbow trout to dry pellet and low-fat herring diets |
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Authors: | K Ruohonen D J Grove † |
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Institution: | Finnish Game and Fisheries Research Institute, Evo Fisheries Research and Aquaculture, 16970 Evo, Finland;Marine Science Laboratories, Menai Bridge, LL59 5EY, Gwynedd, U.K. |
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Abstract: | Long-term voluntary-feeding experiments were carried out on farmed, 2-year-old rainbow trout offered a commercial dry feed, or chopped low-fat Baltic herring. Despite large differences in dietary water, protein and lipid content, the trout adjusted their intake to consume similar amounts of dry matter. After an 18-week trial, the stomach volumes of the herring-fed trout were significantly larger (30–35%) than those fed on the dry diet. Greatest differences were observed when fish were fed one meal per day; increasing the number of daily feeding opportunities reduced these expected stomach volumes on each diet by 15–20%. The relative increase in stomach volume was shown to be due to growth of the cardiac stomach region (corpus) rather than the pyloric region, and not to muscle relaxation; the change was completed within 10 weeks. Data were collected in a separate study to investigate stomach size in fish (age 0+, 1+, 2+) of similar genetic backgrounds which had been grown using dry pelleted diets. Despite considerable variation between populations, stomach volume to body weight relationship was allometric ( S = a W b) with the exponent in the range of 0.3–0.4. |
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Keywords: | rainbow trout stomach volume dietary water |
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