Utilização de subprodutos de cervejaria em dietas para juvenis de tilápia do Nilo

Abstract

The objective of this study was to determine the apparent digestibility coefficients (ADCs) of protein, energy, calcium, phosphorus, and amino acids, constituents of brewery dry residue (BSG), and to evaluate the effects of different levels of inclusion of this residue in the diet on the growth performance and histology of the intestine and liver of juvenile Nile tilapia (Oreochromis niloticus). For the digestibility study, fish (n = 320; 80/tank; average body weight = 13 ± 5.20 g) were randomly distributed in four 200 L cylindrical fiberglass tanks and fed two diets: a reference diet and a test diet containing BSG. The ADCs of protein (67%) and amino acids were considered high, indicating that the tested ingredient had good absorption. The high fiber content may have contributed to the low energy absorption, generating negative ADC values. Due to its low cost, wide availability, composition, and nutrient digestibility, BSG showed potential for use in diet formulation for Nile tilapia. For the work on performance and histology, a completely randomized design in quadruplicate was adopted, in which 300 juvenile Nile tilapia (5.07±0.97g) were placed in 20 polyethylene tanks with a capacity of 60 L (15 fish/experimental unit) and fed, until apparent satiety, four times a day (07:00; 11:00; 15:00 and 18:00), for 43 days. For this purpose, five experimental isoprotein (320 g protein kg-1) and isoenergetic (3,400 kcal kg-1) diets with increasing BSG concentrations (0, 5, 10, 15, and 20%) were formulated. At the end of the experimental period, zootechnical performance and histology of the intestine and liver were evaluated. The data obtained were subjected to one-way ANOVA and Tukey's test (p<0.05). The dietary inclusion of up to 20% BSG did not affect weight gain (p>0.05). The inclusion of 15% BSG in the diet provided the best results in terms of feed conversion rates and protein efficiency (p<0.05). Fish fed diets containing BSG showed no histological alterations in the intestine and liver. The inclusion of 15% BSG in diets for juvenile Nile tilapia is recommended.