Effect of Feeding Frequency on Anxiety-Like Behavior and Cortisol Levels in Group-Housed Zebrafish (Danio rerio)

As the popularity of the zebrafish (Danio rerio) model increases, it is critically important to establish standardized care (husbandry) procedures. Standardization ensures that subjects are treated similarly, eliminating some variability between laboratories, as has been observed in pharmacological and environmental stress studies. Previous research demonstrated that the feeding regimen of zebrafish modulates stress responses. The current experimental study was designed to clarify the impact of feeding regimen in group-housed, adult zebrafish by assessing anxiety-like behavior and basal (baseline) cortisol levels after fish (N = 36, housed at a density of five fish/liter) were fed either once or twice per day for two weeks. Based on previous research, we hypothesized that zebrafish fed twice daily would demonstrate lower levels of anxiety-like behavior (i.e., increased exploration in the novel tank test) and have decreased basal levels of cortisol compared to zebrafish fed once daily. However, there were no significant differences (p > .05) in anxiety-like behavior or basal levels of cortisol between the two groups. This suggests that feeding once vs. twice per day in group-housed fish, at least in the short-term, had no effect on basal stress responses. It is possible that feeding frequency could impact stress responses with longer habitation in a research facility, although further studies are necessary to clarify. The current findings emphasize the need for a full understanding of how care, including feeding, influences neuroendocrine and behavioral endpoints in zebrafish subjects used in biobehavioral research, an important research area critical for understanding human conditions, such as anxiety-related disorders.