Effects of probiotic interventions on production efficiency, survival rate, and immune responses of Macrobrachium rosenbergii (de Man) prawns: A meta-analysis and meta-regression

Probiotics are widely used in commercial shrimp aquaculture, but responses are variable. The objectives of this study were to quantitatively review using meta-analysis the production, survival, and immune responses of Macrobrachium rosenbergii to probiotics and to identify sources of residual variation. A total of 58 comparisons from 16 experiments (full text articles) were included in the final meta-analyses. Classical meta-analysis was used to analyse differences in responses by weighted mean difference (WMD) and standardised mean difference (SMD). Estimates were pooled using DerSimonian and Laird random effects models (D & L); nesting of treatment comparisons within experiment were accounted for by robust regression models (RR). The RR were also used to assess the influence of covariables: initial body weight (BW), method of delivery (feed or water), number of days of probiotic delivery, developmental stage (juvenile or post-larval), probiotic concentration, probiotic genus (Bacillus or Lactobacillus), and diet on the outcomes. Probiotics increased final BW by 1.87 SMD (95% CI = 0.28 to 3.46) and weight gain percent by 1.57 SMD (95% CI = 0.14 to 3.00), compared to the reference prawns. Feed to gain was improved with probiotics by 0.53 g/g (16.7%) or 1.61 SMD (95% CI = 2.63 to 0.60) with greater efficiency for Bacillus probiotics compared to Lactobacillus (SMD = 3.40; 95% CI = 4.66 to 2.14). Specific growth rate was increased by 0.21% per d (95% CI = 0.09 to 0.32), an improvement of 11.2% or 1.32 SMD (95% CI = 0.38 to 2.25) and survival rate by 1.03 SMD (95% CI = 0.21 to 1.85). Probiotics influenced immune and haemolymph measures by D&L evaluation but not RR, suggesting more experiments are required in this field. The outcomes were considerably heterogeneous, indicating a large amount of residual variation was attributable to study conduct. The variance for RR models was low signifying that accounting for the effects of comparison within experiment explained much of the variance. Covariables rarely explained the variation and were not consistent across outcomes. In summary, interventions with probiotics in M. rosenbergii improved growth performance and survival, may be influenced by probiotic agent, and are likely to lead to economic benefits for industry.