The fish reached weights of 72, 72, 69 and 53 g on the 0, 17, 34 and 52 diets, respectively. The 52 diet gave the lowest specific growth rate (SGR, 1.95% day鈭?#xA0;1) relative to those found for the other three diets (2.32% day鈭?#xA0;1). The 52 diet produced the least satisfactory results for feed intake (FI) and the food conversion ratio (FCR) (2.23 g 100 g fish鈭?#xA0;1 day鈭?#xA0;1 and 1.38, respectively). The efficiency of retention of His, Phe and Leu in the fish fed the 52 diet showed the lowest values (17.3, 25.5 and 28.5%, respectively), but the efficiency of retention of Met in the fish fed the 52 diet showed the highest value (48.2%).
In the distal intestine and liver, histological alterations were found in the fish fed the 34 and the 52 diets. In fish fed the 52 diet, the mucosal fold was significantly shorter and thinner and exhibited a smaller number of goblet cells. These changes could affect nutrient uptake by modifying the digestibility of the diet. The histology of the liver did not show severe degradation in any treatment.
The results of the present experiment demonstrated that CG can be included at levels up to 34%in diets for short term feeding of gilthead sea bream without any adverse effects on fish growth and nutritive parameters.