Effect of feed restriction and refeeding on body condition, digestive functionality and intestinal microbiota in rainbow trout (Oncorhynchus mykiss)

Abstract

The aim of the present work was to investigate the influence of fasting and refeeding on body condition, gut physiology and microbiota in reared O. mykiss. Ninety-six fish were randomly allotted among three groups subjected to different feeding plan: C (control, fed for 5 weeks); R (restricted ration over 3 weeks followed by 2 weeks feeding); F (fasted over 3 weeks followed by 2 weeks feeding) in a well’s fresh water flow-through rearing plan. Sampling occurred at 0, 1, 2, 4, 7, 14 days during the refeeding period. At day 0 and throughout the feeding period until day 14, the weight of the fish was significantly affected by the feeding restriction. Feed deprivation reduced significantly the viscerosomatic and hepatosomatic indexes. Brush border membrane enzymes’ specific activity was modulated by feeding regimes until day 7, to level in all experimental groups at day 14. At the end of the restricted/fasted period, the microbiota of the C group was made up of 70% of Actinobacteria, 24% of Proteobacteria, 4.2% of Firmicutes and < 1% of Bacteroides, while the restricted and fasted group were characterized by a strong reduction of Actinobacteria, and a significant increase in Bacteroidetes and Firmicutes. The feed deprivation determined a dysbiosis, allowing the development of different commensal or pathogenic bacteria. In conclusion, the effects of 2 weeks of feed deprivation, excluding those related to body weight, are gradually mitigated by refeeding, which allows the restoration of digestive functions and a healthy intestinal microbiota.

The Beneficial Effects of Dietary Interventions on Gut Microbiota—An Up-to-Date Critical Review and Future Perspectives

“…Another phylum of great interest is Bacteroidetes, which is often assessed in conjunction with Firmicutes. Among the studies that refer to the Bacteroidetes levels, three have observed a corresponding increase [59,60,65,71], whereas one study also indicated a decrease in Firmicutes [65]. The decreased Firmicutes/Bacteroidetes ratio linked to IF was previously identified by other researchers [68,87].…”

“…The microbial community in trout intestines can be significantly influenced by two weeks of feed deprivation [59]. Dysbiosis was characterised by a significant increase in Bacteroidetes and Firmicutes and a reduction in the Actinobacteria population.…”

“…Comparing the information regarding the variation of different types of bacteria in animals, the most frequently studied phylum was Firmicutes. However, the results are contradictory, as some studies reported an increase in the abundance of Firmicutes [56,59,60,71], but others mentioned the reduction of its proportion in the gut microbiota after 24:24 h or 16:8 h IF regimens [62,65,67]. Another phylum of great interest is Bacteroidetes, which is often assessed in conjunction with Firmicutes.…”