A meta-analysis on the influence of dietary betaine on the growth performance and feed utilization in aquatic animals

Betaine is one of the most widely used attractants in feed formulations. Its dietary inclusion in aquafeeds positively influences several growth performance metrics and feed utilization of aquatic animals. In this study, a meta-analysis was conducted to quantify the effects of dietary supplementation of betaine on the specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), and survival (SUR) of several aquaculture species reared under different environmental conditions. Standardized mean differences (Hedge 's g ) were computed to quantify the primary outcomes. Likewise, the influence of several moderators such as aquaculture species, feeding behavior, experimental duration, and percentage of betaine supplementation in aquafeeds on Hedge 's g effect sizes for SGR, FCR, PER, and SUR was determined by a mixed-effects model. The results indicated improved SGR, FCR, and PER in both carnivorous and omnivorous/herbivorous species fed on betainesupplemented diets relative to the control. Although SUR was higher in control groups relative to the betainesupplemented groups, no significant differences were noted. Higher values for betaine inclusion level tended to lower SUR whereas lower values improved the SUR. Furthermore, longer experimental durations exhibited higher values for SUR compared to shorter experimental durations. The dietary betaine requirement of aquaculture animals was estimated to be 0.99 % based on broken-line regression between the betaine inclusion level in aquafeed and SGR effect sizes.