Abstract
The present study evaluated the effects of feed supplemented with two dietary sources of n-3 polyunsaturated fatty acids (PUFAs; fish oil and extruded flaxseed) on the gut microbiota, caecal fermentations, gastrointestinal histology, and histochemistry in rabbits. Fifteen male New Zealand White rabbits were divided into three groups (n = 5/group) and fed with different diets from weaning (35 days of age) until slaughtering (90 days of age): C group, fed with a commercial diet; F group, supplemented with 10% of extruded flaxseed; and O group, supplemented with 3.5% of fish oil. At slaughter, the content of the stomach, duodenum, jejunum, ileum, caecum, and colon was collected and analyzed by Next Generation 16S rRNA gene sequencing. Tissue samples of the same tracts were evaluated with histological and histochemical analysis. Ammonia and lactic acid in the caecum were also quantified. Twenty-nine operational taxonomic units (OTUs) were significantly different between groups. Groups receiving n-3 PUFAs supplementation showed an increase in Bacteroidetes and Lachnospiraceae in several gastrointestinal tracts, while Bacilli abundance, as well as Firmicutes/Bacteroidetes ratio, were reduced compared to the control group (for all p < 0.05). Caecal ammonia was lower in the F than C group (p < 0.032), whereas no difference was found for lactic acid. Finally, histological evaluations revealed a mild hemorrhagic infiltration and vessels ectasia in the stomach mucosa of both F and O groups, but no effect of nutritional treatment was evidenced by the histochemical analyses. In conclusion, n-3 PUFAs supplementation could modify the rabbit gut microbiota and fermentation. The increase in beneficial bacterial populations may, at least partially, explain the positive effects of n-3 PUFAs diet supplementation on human and animals’ health, although the appropriate dosage should be established.
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Key points
In this study, it was hypothesized that n-3 PUFAs-enriched diets influence bacterial richness and diversity of rabbits’ digestive system. The aim was to evaluate the effect of flaxseed and fish oil supplemented diets on the gut microbiota composition in stomach, duodenum, jejunum, ileum, caecum, and colon of rabbits using next-generation 16S rRNA gene sequencing. In addition, histology and histochemistry were performed on the same sections of the digestive system. Finally, lactic acid and ammonia produced by the cecal bacterial fermentations were also quantified.
This study showed that n-3 PUFAs-enriched diets influence bacterial richness and diversity of the rabbit’s gut microbiota. Changes in microbial community composition and diversity, involving Firmicutes/Bacteroidetes ratio and Lachnospiraceae taxa, may contribute to the beneficial effects of n-3 PUFAs. These preliminary results on effect of dietary supplementation with flaxseed and fish oil on the gut microbiota composition of rabbits could represent the starting point for future research to evaluate whether these changes in bacterial populations may also modify the cecal fermentative production of volatile fatty acids. The relationship and the connection pathways between the changes in the gut microbiota and the efficiency of the immune system of the host could be investigated. Moreover, bioactive components of flaxseed and fish oil other than PUFAs could intervene in this relationship, and further research should focus on their role in gut microbiota changes. In particular, n-3 PUFAs supplementation increased some beneficial populations such as Bacteroidetes and Lachnospiraceae while reducing Bacilli and the Firmicutes/ Bacteroidetes ratio, usually associated with metabolic disease, opening interesting scenarios about the reduction in the use of antibiotics in rabbit farms. Targeting the gut microbiota populations composition and its metabolic activity with the diet could be a promising strategy, not only to maintain intestinal homeostasis, but also to control the immune as well as inflammatory response, and consequently, the incidence of gastrointestinal disorders of the rabbit. The appropriate quantity of flaxseed and fish oil to introduce with the diet to favor the right prebiotic action should be, however, optimized.