An experiment with 0.2-kg Atlantic salmon, Salmo salar in saltwater was conducted to determine if the ®sh could grow normally, and maintain normal nitrogen (N) and mineral balance when fed a diet with the majority of the protein (75%) derived from soy-protein concentrate (SPC). The two diets contained 50% SPC and 15% ®sh meal (FM) or 60% FM as the sources of protein. No calcium phosphate was added to the diets in order to assess the availability of P from the ingredients. A second aim was to investigate if wholebody concentrations of essential elements and growth were related in individual salmon.Growth (SGR 0.88±0.89) was similar in salmon fed the two diets, and the ®sh nearly doubled their body weights during the 84 days of feeding. Feed conversion was more ecient for the FM diet (0.81 kg intake kg )1 gain) than for the SPC diet (0.89 kg kg )1 ). The intake of N was similar, faecal loss of N was lower, while the metabolic N excretion was greater in the ®sh fed the FM than the SPC diet. This resulted in a total excretion of 35.4 g N kg )1 gain for the salmon fed the FM diet and 35.5 g N for the ®sh fed the SPC diet. Both the intake, faecal and metabolic excretion of P were higher in the ®sh fed the FM diet than the SPC diet, resulting in a total excretion of 10.5 g P kg )1 gain for the FM diet and 7.2 g P for the SPC diet. Whole-body concentrations of Ca, Mg, P and Zn were lower in the ®sh fed the SPC diet, while the Ca±P ratio was decreased, both when compared with the ®sh at the start of the experiment, and the ®sh fed the FM diet. The dierences in elemental composition were ascribed to a combination of reduced availability of elements due to phytic acid and lower concentration of elements in the SPC than in the FM. No reduction in growth of individual ®sh, which could be ascribed to reduced availability of essential elements, was seen. KEY WORDS

The influence of dietary cholesterol (CHOL) and short‐chain fatty acids (SCFA; sodium salts of acetic, propionic and butyric acid, 5:5:2 w/w/w) on growth, organ indices, macronutrient digestibility, and fatty acid composition of Atlantic salmon Salmo salar was investigated. Salmon (initial average weight 0.7 kg) held in seawater (7°C) for 175 days were fed one of six diets: 1, without CHOL/SCFA supplement; 2, with 0.5% SCFA; 3, with 2.0% SCFA; 4, with 1.0% CHOL; 5, with 1.0% CHOL and 0.5% SCFA; 6, with 1.0% CHOL and 2.0% SCFA. Neither SCFA nor CHOL supplements had any significant effects on specific growth rate (SGR), mortality, apparent digestibility coefficients (ADC) of macronutrients, total lipid content. Hepatosomatic index (HSI) was slightly increased in salmon fed the CHOL supplement (P < 0.05). Hepatic CHOL concentration, but not the hepatic CHOL pool, was significantly increased (P < 0.001) by dietary CHOL supplementation. The fatty acid compositions of fillet and gut tissues were not influenced by dietary treatment, while significant effects of CHOL supplements were observed in faeces and liver. Less saturated fatty acids and more mono‐ and poly‐unsaturated fatty acids were excreted with faeces in salmon fed CHOL supplements. Salmon fed CHOL supplements significantly reduced the relative concentration of hepatic palmitic acid (C16 : 0), arachidonic acid (C20 : 4 n‐6) and docosahexaenoic acid (C22 : 6 n‐3), while the contents of oleic acid (C18 : 1 n‐9) and eicosenoic acid (C20 : 1 n‐9) were significantly increased. SCFA did not influence the observed effects of dietary CHOL. The present study shows that dietary CHOL supplements profoundly altered excretion and liver metabolism of individual fatty acids in salmon. The impact of this alteration on physiological performance has not been elucidated.

Four extruded diets, differing in grain supplementation, were fed to triplicate groups of Atlantic salmon (Salmo salar, L.) with a mean weight of 0.5 kg in a digestibility trial. The diets contained 100 or 150 g kg−1 of precooked rye or wheat, replacing fish meal. There were no significant differences in apparent digestibility coefficients (ADC) of protein, fat or starch which could be related to dietary carbohydrate source or inclusion level. The ADC of dry matter and energy were higher for the diets with wheat than for those with rye, and higher for the diets with wheat than for those with rye, and higher for the diets with 100 g precooked grain kg−1 than for those with 150 g kg−1. The mean ADC of starch was 52% for rye, and 53% for wheat.