Probiotic dietary supplementation in Nile tilapia as prophylaxis against streptococcosis

Abstract

This study evaluated the effects of the probiotic Lactobacillus plantarum as dietary supplement on growth performance, haemato-immunological responses, microbiology, histology and transmission electron microscopy of the intestinal epithelium of Nile tilapia challenged with Streptococcus agalactiae. Fish were distributed into two groups: control (unsupplemented) group and the group fed L. plantarum supplemented diet for a period of 58 days. We observed an increase in the concentration of lactic acid bacteria and a reduction in the number of Vibrionaceae in supplemented fish. A significant increase in the final weight, specific growth rate and feed efficiency was also observed in supplemented fish. After challenge, the number of thrombocytes and neutrophils also increased in supplemented animals. Transmission electron microscopy showed damage to the intestinal mucosa and the presence of bacteria similar to S. agalactiae in both infected groups. L. plantarum colonized the intestines of fish, enhanced the growth performance and modulated some haematological parameters.