Increase of the dietary n - 3/n - 6 fatty acid ratio and addition of phosphorus improves liver histological alterations induced by feeding diets containing soybean meal to gilthead seabream, Sparus aurata

Abstract

In a previous study, several histological alterations were found in the liver of gilthead seabream fed with a diet containing 30% soybean meal (SBM). In the current study, SBM containing diets were supplemented with either potassium phosphate, zinc sulfate or phytase (Aspergillus ficuum), or increasing the dietary n−3/n−6 fatty acids ratio to meet that of a fish meal based diet. Diet composition did not affect fish growth, feed efficiency (FE) or protein productive value (PER). Phosphorous supplementation significantly reduced hepatosomatic indexes (HSI), although it did not alter liver lipid content. Both phosphorous supplementation and correcting the dietary n−3/n−6 fatty acid ratio significantly altered the lipid and protein content in fish muscle. Only these two treatments and principally the corrected dietary n−3/n−6 fatty acid ratio, improved the liver histological alterations observed in fish fed with SBM based diets.