Current Feeding Practice of Xenopus laevis in a Laboratory Setting

SIMPLE SUMMARY: The standardization of husbandry conditions, feeding regimens, and diets is the prerequisite for the comparability of results generated by the use of laboratory animals. Compared to rodents, which account for the largest proportion of laboratory animals worldwide, standardization is still inadequate for aquatic species, especially clawed frogs (Xenopus laevis). In this context, species-specific feeding is important for standardization and animal health and welfare. However, the current feeding recommendations for Xenopus are extrapolated from other species’ nutrient requirements. In addition, the feeding regimen itself affects animal behavior. In particular, the feed intake seems to be influenced by the type of feed. Using a questionnaire, the most common methods of husbandry and feeding of Xenopus laevis in laboratory settings were recorded, and the feeds were compared to the recommendations by Ferrie. The results showed variations with regard to husbandry and feeding concepts between facilities. Commercial Xenopus diets and fish feed were the most commonly used feeds, all meeting the recommendation for protein content but differing considerably in mineral content (based on labelled information). It appears that the feed composition and feeding regimen need to be the focus of further research to ensure that feeding and husbandry are adapted to nutritional and behavioral needs. ABSTRACT: African clawed frogs are common animal models used in various research areas. However, husbandry and especially feeding regimens are not nearly as standardized as is established for other laboratory animals. We recorded the diets and feeding protocols commonly used in laboratory practice in a questionnaire (18 responses). The survey revealed a wide variety of housing conditions. Feeding protocols and, in particular, diet composition varied considerably between facilities. While diets tailored to Xenopus were used in the majority, differences in feeding frequency and dietary components were noted. From five responses, the weekly feed intake per frog could be calculated, showing considerable differences in dry matter intake (1.37–5.4 g). The labelled nutrient content of the diets fed in the facilities (n = 10) met the recommendations in most cases, with protein as the major energy source. However, the mineral content varied markedly between diets. Both floating and sinking diets were used, while quickly sinking diets were associated with feed leftovers. Feed processing may likely influence feed intake behavior. Further research is needed to ensure standardization for aquatic species with respect to husbandry systems, feeding regimens, and especially the nutrient composition of feeds. Furthermore, this work will contribute positively to animal welfare and the comparability of research results.