The Roles of Enzymes as Dietary Additives in Ruminant Diets: A Meta-Analysis

Understanding the function of enzymes before their use as additives in ruminant diets is essential for achieving sustainable and efficient agricultural practices. Ruminants such as cattle, sheep, and goats are vital for global food production because of their ability to convert fibrous plant materials into high-quality proteins through enteric fermentation. Various datasets were carefully selected from four scientific databases: Science Direct, Scopus, PubMed, and Google Scholar. The rigorous Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) protocol was employed to ensure the eligibility of the selected articles used in the analysis. A systematic review showed that the administration of various types of enzymes can increase dry (DMD) and organic (OMD) matter, neutral (NDFD), and acid (ADFD) detergent fibre, and crude protein (CPD) digestibility in both in vitro and in vivo tests in individual studies. However, the pooled meta-analysis indicated that their overall effect on CPD was not significant (p > 0.05). The OpenMEE approach was used to calculate the effect size (Hedges' g) for each experimental unit for various parameters. Across enzyme types and doses in the meta-analysis, the administration of enzymes did not have any significant effect (p > 0.05) on DMI, OMI, and CPD, but it did have a significant effect (p < 0.05) on DMD, OMD, ADFD, NDFD, pH and gas production at 24, 48, and 72 h, as assessed by in vitro experiments. Ruminant in vivo studies indicated that the administration of enzymes has significant impacts (p < 0.05) on digestibility parameters (DMD, OMD, NDFD, ADFD), milk production, milk lactose content, acetate, and propionate, but it had non-significant impacts on milk protein and rumen total volatile fatty acids and acetate: propionate ratio.