LONG TERM FEEDING OF VEGETABLE OIL BASED DIETS AFFECTS MUSCLE CELLULARITY AND THE EXPRESSION OF GROWTH-RELATED GENES

Abstract

Texture is one of the most important aspects related with fish quality. Being a sensory attribute of flesh capable of influencing consumers’ acceptance, texture assumes a major role in species with high economic value, like Senegalese sole. Several intrinsic and extrinsic attributes are capable of influencing flesh texture, and fish diet is one of those. The sustainable growth of the aquaculture sector depends on finding alternative sources for aquafeeds, reducing the use of fish meal (FM) and fish oil (FO). Vegetable oils (VO) are a feasible alternative to FO, but have significant impacts on flesh quality. Most studies evaluated the impact of such diets on the nutritional value of the fillet, but few focused on organoleptic attributes and even less on textural properties. Textural properties can be accessed through muscle cellularity and gene expression. The aim of this work was to evaluate the effect of increasing dietary levels of VO (50%, VO50 and 100%, VO100) in muscle cellularity and gene expression of Senegalese sole juveniles fed the experimental diets for 140 days. The total substitution of FO by VO (VO100) significantly increased the cross sectional area (CSA) of Senegalese sole (P<0.05) and reduced the number of white muscle fibers/mm2 compared to the other treatments. On the other hand, fibers area (µm2) of fish fed VO100 was significantly higher than those fed the CTR and VO50. The dietary inclusion of VO had no effect on fish length and weight neither on the total number of fibers per CSA. The relative expression of 13 genes related to muscle differentiation and growth, standardized with 2 reference genes, were studied. No statistical differences were reported for the expression of myogenic regulatory genes or the insulin growth factor II (igf-II) in fish fed the VO diets compared to the CTR. However, the expression of the growth factor igf-I was significantly higher in fish fed VO100 contributing to a higher white fiber area in this fish.