Supplemental citric acid and particle size of fish bone-meal influence the availability of minerals in rainbow trout Oncorhynchus mykiss (Walbaum) |
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Authors: | VIELMA RUOHONEN & LALL |
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Institution: | Finnish Game and Fisheries Research Institute, Laukaa Fisheries Research and Aquaculture, FIN-41360 Valkola, Finland; Finnish Game and Fisheries Research Institute, Evo Fisheries Research and Aquaculture, FIN-16970 Evo, Finland; Institute for Marine Biosciences, National Research Council of Canada, Halifax, NS, Canada B3H 3Z1 |
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Abstract: | Juvenile rainbow trout Oncorhynchus mykiss (Walbaum) were fed six low-phosphorus (P) diets supplemented with two different sizes of ground fish bone-meals (fine, 68 μm or less; coarse, 250–425 μm) and a coarse bone-meal diet containing four levels of citric acid (0, 4, 8 or 16 g kg?1 diet) to investigate the effects of pH and bone particle size on P bioavailability. The basal diet provided 3.4 g P kg?1 and bone-meal increased P contents to 5.4–6.0 g P kg?1. Coarse bone-meal diets supplemented with 0, 4, 8 or 16 g kg?1 of citric acid had pH values of 6.0, 5.7, 5.4 and 5.0, respectively. Weight gain and whole-body water, protein and lipid contents were not influenced by bone-meal supplementation. Supplementing the basal diet with both coarse and fine bone-meal significantly increased whole-body ash content. Fish fed no bone-meal were hypophosphataemic compared with fish fed with either fine or coarse bone-meals. Phosphorus in fine bone-meal had higher availability than P in coarse bone-meal. Bone-meal supplementation significantly decreased whole-body manganese content from 8.9 μg g?1 in fish fed no bone-meal to 2.3 and 4.5 μg g?1 in fish fed with fine and coarse bone-meals, respectively. The concentration of magnesium increased but zinc concentration was not affected by bone-meal supplements. Citric acid increased whole-body ash content but the influence of citric acid on the body P content was not significant ( P = 0.07). Dietary acidification by citric acid significantly increased whole-body iron in a linear fashion. The bioavailability of dietary P can be improved by fine grinding the bone in fish meals. |
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Keywords: | citric acid digestibility fish bone-meal particle size phosphorus rainbow trout |
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