Chitin in Aquafeeds: A Meta-Analysis of Fish Growth Performance and Nutrient Digestibility

Abstract

Chitin is a structural polysaccharide in arthropod exoskeletons and fungal cell walls and is introduced into aquafeeds through ingredients such as insects, krill, shrimp, and yeast. This study applied a meta-analytical approach to evaluate the effects of dietary chitin-containing ingredients and dietary chitin content on fish growth performance and nutrient digestibility, and to develop regression models identifying factors influencing fish responses to chitin. The pooled effects indicated that the dietary inclusion of krill, shrimp, and yeast improved fish growth without affecting feed intake, whereas insect-based diets reduced growth, and insects and yeast reduced nutrient digestibility. However, these overall effects varied across fish trophic levels. Notably, insect-based diets decreased growth in higher trophic species but promoted growth in lower trophic species. Meta-regression analysis showed that dietary chitin content partly explained the heterogeneity in effect sizes for growth performance and protein digestibility in insect-based diets. Segmented regression showed a marked decline in fish growth above 2.91% dietary insect chitin. Multiple regression models indicated that trophic level and study duration influenced fish growth responses to dietary insect chitin, while initial body weight affected nutrient digestibility responses to chitin. At comparable study durations, lower dietary chitin contents maintained stable growth across trophic levels, whereas growth declined progressively with increasing chitin levels, with the steepest reductions observed in higher trophic species. These findings demonstrate that dietary chitin content, trophic level, study duration and initial body weights are key factors shaping fish responses to chitin, providing a quantitative basis for optimizing chitin-containing ingredients inclusion in aquafeeds.