META-ANALYSIS OF RESPONSES OF SMALL RUMINANTS TO DIETARY PHYTOGENIC FEED ADDITIVE INTERVENTION

There are conflicting findings on the effect of phytogenic feed additives (PFA) on the productivity of small ruminants.The objective of this meta-analysis, therefore, was to evaluate the efficacy of PFA intervention in improving dry matter intake (DMI), ruminal fermentation, serum biochemical markers, and milk production in small ruminants.Studies on Scopus, Web of Science, ScienceDirect, Google Scholar, and PubMed were searched.Among the 852 articles retrieved, 14 were used for the analysis.Effect size was calculated using the random-effects model, and results were displayed as standardised mean differences (SMD) at 95% confidence intervals (CI).Results showed that methane production (P = 0.007), acetate production (P = 0.030), and acetate-to-propionate ratio (P = 0.019) were reduced by PFA with evidence of significant heterogeneity.In contrast, concentrations of total volatile fatty acids (P = 0.046) and propionate (P = 0.039) were increased by PFA intervention.Serum total proteins (P = 0.009) and serum glucose (P = 0.028) were increased, whereas serum urea was decreased (P = 0.009) by PFA intervention.Egger's test suggested no publication bias.Subgroup results showed that PFA intervention decreased methane production while increasing propionate production in sheep compared to goats.Meta-regression showed that moderators were significant predictors of the treatment effect on aspects of ruminal fermentation parameters and explained most of the heterogeneity in the effect of PFA intervention on ruminal fermentation parameters in small ruminants.These results suggest that PFA intervention enhanced ruminal fermentation and serum biochemical markers in small ruminants while reducing methane production.