Effect of diets containing different types of sardine waste (Sardinella sp.) protein hydrolysate on the performance and intestinal morphometry of silver catfish juveniles (Rhamdia quelen)

In this study two fractions of muscle hydrolysate were tested, soluble and insoluble (FSM and FIM), they were assessed individually and combined with each other (FSM+FIM). Also, two fractions of hydrolyzed viscera: soluble of natural and industrialized viscera (FSVN and FSVI) were tested on the performance and on the intestinal morphology of juvenile catfish (Rhamdia quelen). The experimental design was completely randomized with five treatments and five replicates. Juveniles were kept in aquariums with density of eight fish per tank and were cultured for 56 days. The results were analyzed using parametric variance analysis (ANOVA) and subjected to the Duncan test (5% significance level). The best results on final weight, weight gain, feed conversion rate, and protein efficiency ratio were obtained with the diet containing FSM+FIM, and the diet containing the FSVI. The latter was also the most consumed by the animals. The diet containing FIM was the one that provided the worst consumption results. The worst feed conversion rate was obtained for the diet containing FSM. Survival and body composition did not differ between treatments. The separation of the soluble and insoluble fractions is not necessary or even recommended when the goal is to use the muscle hydrolysate as the ingredient in feed for silver catfish juveniles. The best performance results obtained were with the combination of soluble and insoluble fractions of muscle hydrolysate, and with the industrial viscera soluble hydrolysate. The degree of hydrolysis has a direct effect on feed consumption.