Post weaning diarrhea remains a major challenge in swine production, and bacteriophages are increasingly explored as alternatives to antibiotics.This meta-analysis quantified the effects of bacteriophage therapy on bacterial load in piglets and examined factors contributing to variation in treatment outcomes.A multi database search identified 85 effect size comparisons from 11pathogen challenge studies involving 198 piglets.Standardized mean differences (SMDs) were calculated using multilevel random-effects models, and heterogeneity, variance components, publication bias, and moderator effects were assessed.Among evaluated moderators, only challenge pattern significantly explained variation in effect sizes (Q = 11.72,df = 5, p = 0.039), while all other moderators were not statistically significant (p > 0.05).Within moderators, some trends emerged.Prophylactic dosing produced a moderate and highly consistent reduction (SMD = -0.64,p < 0.001; I = 19.41%),whereas therapeutic dosing produced a larger but more variable effect (SMD = -1.29,p < 0.001; I = 66.77%), based on few effect sizes.Reductions were significant for both Escherichia coli (SMD = -0.79,p = 0.014) and Salmonella (SMD = -0.90,p < 0.001) challenge trials.Encapsulated phages produced larger reductions than non-encapsulated formulations (SMD = -1.51,p = 0.026; SMD = -0.70,p < 0.001), although moderator test was not significant.Single-phage preparations produced larger reductions (SMD = -1.13,p < 0.001) than cocktails (SMD = -0.59,p < 0.001), whereas cocktails showed more consistent responses than single phages (I = 33.47%compared with 55.39%).In-feed delivery yielded more consistent outcomes than oral gavage (I = 21.98% compared with 63.91%).Assessment of publication bias did not indicate the presence of small-study effects (Egger's test: p = 0.77).Although slight asymmetry was visible in the funnel plot, this pattern was not sufficient to confirm reporting bias.Sensitivity analyses showed that the pooled effect estimate was stable across influence diagnostics.Overall, the evidence indicates that phage treatment reduced bacterial load in piglets in the included studies, while practical application will likely require further standardization of formulation, delivery, and dosing procedures.
Tolojanahary et al. (Thu,) studied this question.