During the E. tarda challenge test, the first dramatic mortality was observed on the third day after injection, and the fish fed the Con and KH diets showed lower disease resistance compared to those fed the TH diet (Fig. 1). Although fish fed the TH diet exhibited numerically higher disease resistance than the two other experimental groups, the differences were not significant at the end of the challenge test.
The fish fed the KH diet showed significantly (P b 0.05) higher growth performance than those fed the Con diet. Significantly lower feed conversion ratio was obtained in fish fed the KH diet compared to those fed the Con diet. Fish survival varied from 82 to 87% without any significant differences among dietary treatments. Digestibility of dry matter and protein was significantly higher in fish fed hydrolysate containing diets (Table 3).