The effect of dietary canola meal and phytase incorporation on growth and feed utilization parameters in European sea bass (Dicentrarchus labrax L. 1758)

In this thesis, two experiments were carried out in order to determine the effects of canola meal and phytase incorporation into sea bass (Dicentrarchus labrax) diets. In Trial I, it was aimed to investigate the effects of addition of different ratios of canola meal into the diets of juvenile sea bass (1,88 g) on their growth performance and nutrient digestibility. Therefore, 5 different experimental feeds were designed. The control diet contained fish meal as basal protein source, while in the other diets the protein from the fish meal in the diets was substituted by 10% (K10), 20% (K20), 30% (K30) or 40% (K40), respectively. At the end of the 8-week feeding trial, fish fed K30 diet reached the highest final weight (9,68 g), while diets containing canola meal yielded weight gain as good as the control diet. The addition of canola meal into sea bass diets had no effect on the feed conversion ratio (FCR), protein efficiency ratio (PER), net protein utilization ratio (NPUR), condition factor (CF), hepatosomatic index (HSI), and body composition. The highest viscerosomatic index (VSI) and the lowest protein digestibility was determined in fish fed diet K40.In trial II, diets containing canola meal and phytase (1500 U/kg feed) were prepared for juvenile sea bass (9,70 g). The effects of the diets on the growth performance and mineral digestibility of fish were investigated. Fish fed diets K20 (27,45 g) and K20+F (26,41 g) reached the highest final weight and had lower FCR. The addition of phytase had no effect on the weight gain, FCR, PER, HSI and VSI. With the increase of canola meal incorporation, a decrease in phosphorus digestibility was observed, but there was no effect on calcium, magnesium, iron, copper and zinc digestibility. The mineral digestibility increased with phytase supplementation. It was suggested that 30 % of the fish meal protein in juvenile sea bass diets can be replaced with canola meal and phytase supplementation can increase the mineral digestibility.