Cross effects of the strain of dietary Saccharomyces cerevisiae and rearing conditions on the onset of intestinal microbiota and digestive enzymes in rainbow trout, Onchorhynchus mykiss, fry

Abstract

Two strains of Saccharomyces cerevisiae were tested as probiotics for rainbow trout fry, during the first month of feeding. Each strain was introduced into separate diets, at the rate of 106 CFU g− 1 and their effects were compared with those of a control diet. Two rearing conditions were simultaneously compared, to test the adaptability of the probiotic treatment. From start feeding onwards, the water supply came from either spring or river, resulting in two different temperature ranges, 11-11.5 and 7-8 °C respectively. Growth and development were optimal in spring water, while some delay was observed with colder river water. A slight but significant increase in mortality was also observed in the river group. In all groups, the counts of bacteria associated with trout intestine were maximum 10 days post start feeding (dpsf; 107 CFU g− 1). The counts of probiotic yeast were also maximum at 10 dpsf (104-105 CFU g− 1), but the decrease was slower in river than in spring water. An autochthonous yeast, Debaryomyces hansenii, was also retrieved associated to the intestine of the control group in high numbers after 240 degree days of experiment (104-105 CFU g− 1), while the colonization level was significantly less in trout fed the probiotic diets. The effect of the dietary yeast was observed by assaying the activity of three enzymes in the brush border membrane of the enterocytes: alkaline phosphatase (AP), γ-glutamyl-transpeptidase (GGT), and leucine-aminopeptidase N (LAP). At 10 and 20 dpsf, the trout reared in spring water had higher activities of the three enzymes when they were fed the strain S. cerevisiae var. boulardii, suggesting an earlier maturation of the digestive system in this group, compared with trout fed either the other strain of S. cerevisiae or the control diet. The effect was not observed in trout reared in river water with slower growth. Both S. boulardii and D. hansenii seemed to stimulate digestive maturation in fish, but the natural colonization by D. hansenii was likely too late for trout reared at optimal temperature. The supplementation of trout starter diet with S. boulardii may be particularly useful in fast growing conditions.

EFFECTS OF DIETARY COMMERCIAL YEAST GLUCAN ON INNATE IMMUNE RESPONSE, HEMATOLOGICAL PARAMETERS, INTESTINAL MICROBIOTA AND GROWTH PERFORMANCE OF WHITE FISH (Rutilus frisii kutum) FRY

“…Similar benefits have been reported in fish fed dietary glucan (Masahiro, 1999, Meena et al, 2012, Soltanian et al, 2009. Growth rate possibly enhanced due to the energetic benefits obtained through glucan (Ai et al, 2007), microbial manipulation of intestinal microbiota (Ringø et al, 2010), colonization of lactic acid bacteria (as seen in our results; Table 3) in the gut and production of protease and amylase by these bacteria in the digestive tract (Farzanfar, 2006, Gullian et al, 2004, Irianto and Austin, 2002, Waché et al, 2006, Hoseinifar et al, 2011a. In addition, enumeration of LAB increases the concentrations of the volatile fatty acids (VFA s ) which beneficially affect microvillus morphology and nutrient utilization (Daniels et al, 2010, Dimitroglou et al, 2009, Ringø et al, 2010, Salze et al, 2008, Zhou et al, 2010.…”

High or low dietary carbohydrate:protein ratios during first-feeding affect glucose metabolism and intestinal microbiota in juvenile rainbow trout

“…These analyses showed significant differences in the fungal profiles between the two groups of alevins after the first 5 days of feeding. A previous study with culturedependent methods pointed out the importance of early colonisation by yeast in the gut of rainbow trout for the maturation of the digestive system (Waché et al, 2006). In human gut microbiome, the increased abundance of Candida due to high-carbohydrate diets was related to its contribution to starch digestion (Hoffmann et al, 2013).…”

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“…However, for the first time is reported its use in diets with high contents of soybean meal. The improved growth of juveniles fed the Diets Y and Y+Ph might be related to a better nutrient digestibility, particularly the protein fraction (Lara-Flores et al, 2003;Waché et al, 2006) and the results of the present research indicates that yeast might contribute to this. During the feeding trials we were not able to determine the protein digestibility, but Bureau et al (2002) reported that N excretion and oxygen consumption might be useful to estimate the nutrient utilization of diet, as usually, low values indicates a better use of the protein (less N excretion) and less energy spent in its oxidation (less oxygen consumption).…”