Dietary carbohydrate, iron and zinc interactions in Atlantic salmon (Salmo salar)

Atlantic salmon (initial weight 312 g) were fed four experimental diets containing either low (5%) or high (10%) levels of wheat starch, combined with either a low (6 mg kg(-1)) or high (30 mg kg(-1)) iron and zinc level, in order to elucidate interactions between dietary starch and iron plus zinc. No difference in specific growth rate or protein productive value as a consequence of the variations in dietary starch was observed. Protein efficiency ratio was significantly lower in fish fed with 5% compared to 10% starch diets, indicating higher deposition of nonprotein components as a consequence of the higher starch level. Dietary iron plus zinc significantly influenced final weight, condition factor and hepatosomatic index, with lower values in fish fed with higher mineral levels. The present dietary manipulations did not affect blood haematology, with all values being within normal ranges for Atlantic salmon. Plasma levels of glucose, protein, cholesterol or triacylglycerols were not affected by the dietary treatments. Low activities of plasma aspartate amino transferase and alanine amino transferase indicated, along with no mortality, no negative effects on liver function or fish health due to dietary treatments. Glycogen levels in whole body, liver and spleen were increased in fish fed with 10% compared to 5% starch diets. Liver iron concentration was affected by both dietary starch and mineral levels. Whole body homogenates showed significantly higher zinc levels in fish fed with higher iron and zinc diets, whereas plasma zinc levels were affected by dietary starch, iron and zinc levels, which showed a significant interaction effect. (C) 2003 Elsevier Science B.V. All rights reserved.