Background:

Probiotics in aquaculture are becoming important to improve the welfare of fishes because of some benefits to their physiological processes and, consequently, to their growth.

Goals:

To assess the effects of two autochthonous bacterial strains with probiotic features on the Rainbow trout growth and its digestive enzyme activities.

Methods:

In this study, the effect of Bacillus pumilus (BP), Bacillus sp. (BSP) and the mixture (BPSP) was tested on the growth and the activity of digestive enzymes of the Rainbow trout. The autochthonous strains, previously characterized as potential probiotics in vitro, were administered individually at 1 × 107 CFU g-1 food and as a mixture, for the last one the concentration was 0.5 × 107 CFU g-1 of food for each one; during 8 weeks.

Results:

Neither of the strains used generated significant growth, compared to the control. Fishes fed with BSP had a better growth respect to BP and BPSP. The highest activity of enzymes was obtained in the fish treated with bacteria, but only BPSP-treated fish had a significant increase (P < 0.05) in the three enzymes activities, compared to the control. Under the current test conditions, individual strains had no significant effects on growth, but the consortium had a significant increasing effect on enzyme activities.