How Fasting and Refeeding Affects Trout Gut Health

Jim Crocker
18th April, 2024

How Fasting and Refeeding Affects Trout Gut Health

Image Source: Natural Science News, 2024

Key Findings

  • In a study at Université de Pau & des Pays de l’Adour, rainbow trout diets with yeast extract showed potential gut health benefits
  • Short fasting periods followed by refeeding can affect gene expression related to trout's immune and stress responses
  • The study suggests that dietary components, like yeast extract, could enhance fish health in aquaculture practices
In the realm of aquaculture, the nutrition of farmed fish is a critical aspect that directly influences their growth, health, and overall productivity. A new study[1] conducted by researchers at Université de Pau & des Pays de l’Adour sheds light on how the inclusion of yeast extract in a fishmeal-free diet can affect the growth performance of rainbow trout (Oncorhynchus mykiss) and modulate their bodily responses after a short fasting period—a common practice in fish farming operations. The study focused on the impact of a 4-day fasting period followed by an 8-day refeeding phase with different diets on rainbow trout. The diets included a standard control diet containing fishmeal and alternative diets using terrestrial animal by-products, with or without the addition of yeast extract. The research aimed to understand how these diets affect the fish's growth and the expression of certain genes in the liver and intestine, which are crucial for maintaining their physiological functions. During the refeeding phase, the researchers observed that most growth and health parameters showed no significant change in response to the different diets. However, one notable exception was the upregulation of claudin-15, a gene associated with tight junctions in the gut, in fish that received the yeast-supplemented diet. This suggests a potential for improved intestinal barrier function with yeast supplementation. The influence of fasting followed by refeeding was more pronounced. In the proximal intestine, the area of absorptive villi increased, suggesting enhanced nutrient absorption capability. Additionally, the density of goblet cells, which produce mucus to protect the gut lining, tended to decrease during refeeding. While there was no clear plasma immune response or signs of gut inflammation, certain genes involved in liver and intestine structure, immune pathways, and stress responses were significantly regulated by the refeeding after fasting. This study builds upon previous research that has explored the effects of diet and fasting on fish health and immune responses. For instance, earlier studies have shown that certain dietary supplements, such as algal extract containing alginic acid and yeast extract containing beta-glucans, can activate innate immune responses in sea bass[2]. These findings are in line with the current study, suggesting that dietary components can modulate the immune system in fish. Moreover, research on the European eel has demonstrated that short-term starvation does not significantly alter metabolic or non-specific immune parameters[3], indicating an adaptive response to food deprivation. Similarly, the present study found that rainbow trout can cope with short-term fasting without major disruptions to immune function. On the other hand, prolonged fasting in rainbow trout has been shown to lead to significant physiological changes, including reduced body condition and altered immune-related gene expression[4]. The current study did not involve prolonged fasting but suggests that even short-term fasting can have significant effects on gene expression related to immune and stress responses. Furthermore, studies on Atlantic salmon have revealed that fasting and refeeding can significantly affect gastrointestinal morphology and digestive enzyme activities[5]. The current research supports these findings, showing changes in the intestinal structure of rainbow trout during refeeding after fasting. In summary, the study from Université de Pau & des Pays de l’Adour provides new insights into how a yeast-supplemented, fishmeal-free diet can influence the physiology of rainbow trout, particularly after a fasting period. The findings underscore the importance of diet composition in aquaculture practices and suggest that dietary supplements such as yeast extract could potentially enhance fish health and growth performance, especially when fish are subjected to the stresses of routine farming operations like fasting and refeeding.



Main Study

1) Gut physiology of rainbow trout (Oncorhynchus mykiss) is influenced more by short-term fasting followed by refeeding than by feeding fishmeal-free diets

Published 16th April, 2024

Related Studies

2) Short- and long-term effects of a dietary yeast beta-glucan (Macrogard) and alginic acid (Ergosan) preparation on immune response in sea bass (Dicentrarchus labrax).

Journal: Fish & shellfish immunology, Issue: Vol 18, Issue 4, Apr 2005

3) Physiological responses to starvation in the European eel (Anguilla anguilla): effects on haematological, biochemical, non-specific immune parameters and skin structures.

4) Effects of prolonged fasting on levels of metabolites, oxidative stress, immune-related gene expression, histopathology, and DNA damage in the liver and muscle tissues of rainbow trout (Oncorhynchus mykiss).

5) Fasting and refeeding cause rapid changes in intestinal tissue mass and digestive enzyme capacities of Atlantic salmon (Salmo salar L.).

Journal: Comparative biochemistry and physiology. Part A, Molecular & integrative physiology, Issue: Vol 141, Issue 4, Aug 2005

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