Pectic hydrolysates in the diet of Nile tilapia ( Oreochromis niloticus ): Performance, nutritional composition, histological parameters, enzymatic activity, hepatic parameters and intestinal contents

The objective of the work was to investigate the prebiotic potential of pectic hydrolysates extracted from apple pomace and passion fruit peel, added to the diet of Nile tilapia (Oreochromis niloticus). The biological assay introducing pectic hydrolysates in the diet of Nile tilapia (3.9 ± 0.67 g) lasted 42 days. Five experimental diets were evaluated, one of them a control diet and the others with the addition of pectic hydrolysates (2.5 and 5 g/kg). The fish were fed three times a day until apparent satiation. At the experimental end point, the animals were fasted for 18 h and then subjected to biometrics for data collection, tissues and digests for further analysis. The results were subjected to a normality test, followed by analysis of variance, and the means of the treatments were compared by analysing orthogonal contrasts (p < 0.05). The pectic hydrolysates did not significantly influence the performance parameters. The fish had higher body crude protein content and protein deposition with diet control than in diet 2.5 g/kg of passion fruit peel. Fat content and fat deposition were lower in 2.5 and 5 g/kg of passion fruit peel when compared to the control group. The fish feeding with 5 g/kg of apple pomace hydrolysates showed greater trypsin and chymotrypsin activity, elevation of glucose concentrations in the liver and higher acetic acid production. However, further studies should be carried out to define the adequate amounts of pectic prebiotic supplementation, aiming at analysing the effects on Nile tilapia growth and alimentary efficiency, as well as to elucidate their mechanisms of action.