engleski

Effects of a dietary mesophilic probiotic Lactobacillus rhamnosus on physiological responses of rainbow trout

Lactobacillus rhamnosus was mixed in the trout diet with peptone water to attain two diet groups with concentrations of 107 (G1) and 108 CFU (G2). The G3 group was fed with feed sprayed only with peptone water. Fish were fed for six weeks and sampled at the beginning and end of the trial, and three weeks after the feeding trial. Before the trial, fish had no detectable lactic acid bacteria in the intestines nor in the fecal contents. The numbers of viable lactobacilli from fecal contents increased in G1 and G2 from below detection limits (<10 CFU/mL) to levels between 2 x 102 and 4 x 105 CFU/mL (G1), between 4.2 x 102 and 8 x 102 CFU/mL (G2) by the end of the trial. Even G3 demonstrated viable lactobacilli between neglectable to 0.6 x 104 CFU/mL. The feeding with supplemented probiont changed the resident microbiota in fish from Vibrio fluvials, Aeromonas hydrophila, Serratia fonticola before the trial, to V. fluvialis, Burkholderia cepacia, non-fermenter species, and Pasteurellaceae by the end of the trial. For tested plasma metabolites, no significance was found in feeding categories between lower and higher L. rhamnosus concentrations, implying that for the tested variables, a difference in probiont concentration was not as important as duration of treatment in comparison to withdrawal period. A decrease in SOD was noted in the control and both G1 and G2 withdrawal groups, both GSH-Px and PON 1 increased after the withdrawal phase. A significantly higher liver TBARS level was observed in G2 group six weeks after the start of the feeding trial with supplemented diet (G2). Plasma glucose, urea, creatinine, total proteins, albumins, triglyceride, cholesterol, SOD, GSH-Px stood out with a potential to indicate to the impact of probiont upon the overall health status of rainbow trout.

probiotics ; fish ; LGG

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