Effect of commercial probiotics (Bacillus subtilis and Saccharomyces cerevisiae) on growth performance, body composition, hematology parameters, and disease resistance against Streptococcus agalactiae in tambaqui (Colossoma macropomum)

Abstract

The use of feed additives as probiotics in aquaculture is increasing, but it is still poorly understood. Our aim was to evaluate the effect of two probiotics (Bacillus subtilis 10 9 UFC/g and Saccharomyces cerevisiae 10 9 UFC/g) on growth parameters, body composition, and hematological responses of tambaqui juveniles (Colossoma macropomum) by considering time a key factor for the probiotics-pathogens interaction. The first phase studied 108 animals (2.13 ± 0.75 g) randomly distributed into 12 tanks. Weight, consumption, feed conversion, weight gain, survival, and body composition were evaluated after 90 days. The second phase studied 60 animals (175.01 ± 36.73 g) fed with the same experimental diets. After 60 days, fish were induced with bacteria Streptococcus agalactiae strains (1.0 × 10−5 UFC) and subjected to blood collection (0, 12, 24, 48, and 72 h). In short, no differences were observed for performance and body composition. Mortality was not observed for phase 1 and 2, and it is expected due to purposeful protocol of moderate infection. However, improvements of hematological parameters (red and white series) were noted in the tambaqui supplemented with commercial S. cerevisiae when considering exposure time.