‘Postbiotic’ shows promise for rainbow trout
Research has shown that a so-called “postbiotic” given to trout exerted changes in the composition and structure of the intestinal bacterial community of the fish.
This led to greater diversity and bacterial richness, and also conferred greater protection against infection.
Postbiotics are metabolic products or by-products secreted by live bacteria or released after the bacteria break down, and which can provide a physiological benefit to the host.
Unlike probiotics, which are live microorganisms, postbiotics are immobilised.
Lactic acid bacteria
Postbiotics are already used in the production of pigs, poultry and ruminants, and researchers from Spain, Chile and Nicaragua conducted a study to evaluate their effects on rainbow trout.
The scientists first selected two lactic acid bacteria belonging to the genus Lactobacillus and Leuconostoc, originally isolated from rainbow trout. In the laboratory these strains had demonstrated antagonistic activity against Lactococcus garvieae, which causes Lactococosis, a disease that causes septicaemia in several farmed fish species.
The researchers made a postbiotic by fermenting the two types of bacteria then divided a group of 160 fish into three groups and fed 70 fish a diet supplemented with the postbiotic for 30 days.
Slight weight increase
The postibotic had no adverse effect on fish growth, and in fact the study authors observed a slight increase in the weight of fish treated with postbiotics after four weeks.
Additionally, changes in the structure of the intestinal bacterial community were also evident.
“The composition and structure of the bacterial community were significantly different between the treated and control groups. A greater diversity and bacterial richness were found in the intestine samples of the treated fish, compared to the samples of untreated fish,” said the researchers in their results.
Also, they found that the postbiotic conferred greater protection against infection with L. garvieae, since the mortality in the group with the supplement was lower.
Read the abstract of the article entitled "Changes in intestinal microbiota and disease resistance following dietary postbiotic supplementation in rainbow trout (Oncorhynchus mykiss)" here.
