Histopathological and transcriptional scoring of intestinal traits in gilthead sea bream (Sparus aurata) fed low fish meal and fish oil diets with butyrate supplementation

Abstract

The intestinal gut forms a physical barrier that is responsible for the absorption of nutrients from the lumen, but at the same time constitutes a first line of host defence against microbes and their derived products. Therefore, the preservation of the intestinal mucosa following injury or physiological damage is essential to preserve intestine function and to prevent the invasion of harmful luminal factors, which subsequently may lead to inflammation. Experimental evidence in gilthead sea bream highlights that disease resistance against the parasite Enteromyxum leei is highly dependent on dietary fish oil composition (Estensoro et al., 2011). Likewise, dietary intervention also has a major effect on the intestinal mucin pattern analysed by means of histological staining (Estensoro et al., 2012) and gene expression analysis (Pérez-Sánchez et al., 2013). Mucins are therefore emerging as intestinal biomarkers of diagnostic and prognostic value. With the improve of fish feed formulations, it has been proved that growth performance is highly preserved in low fish meal (FM) diets (5% inclusion level), when the theoretical requirements in essential amino acids, fatty acids, phospholipids, vitamins and minerals are met by the diet. However, holistic approaches are needed to fully validate these novel aquafeeds, and the aim of this study is to assess the effects of dietary intervention on intestinal health by means of histopathological and transcriptional approaches in fish fed from early juvenile stages low FM and fish oil (FO) diets, supplemented in the case of the extreme diet with a commercial sodium butyrate preparation.