A meta-analysis of probiotic interventions to mitigate ruminal methane emissions in cattle: implications for sustainable livestock farming

• Published in: Animal (Cambridge, England) England), 2024-06, Vol.18 (6), p.101180, Article 101180
• Main Authors: Ncho, C.M., Kim, S-H., Rang, S.A., Lee, S.S.
• Format: Article
• Language: English
• Subjects: Animal Feed - analysis; Animal Husbandry - methods; Animals; Cattle; Climate change; Cow; Diet - veterinary; Direct-fed microbes; Greenhouse gases; Methane - metabolism; Probiotics - administration & dosage; Probiotics - pharmacology; Rumen - metabolism; Ruminants
• ISSN: 1751-7311; 1751-732X; 1751-732X
• DOI: 10.1016/j.animal.2024.101180

•Several probiotics were tested for enteric methane reduction in cattle.•Probiotics are viable solutions for reducing enteric methane emissions.•Multistrain probiotic formulations are superior.•Extended probiotic supplementation enhances methane mitigation potential.•Long-term probiotic effects on methane emissions need further study. In recent years, the significant impact of ruminants on methane emissions has garnered international attention. While dietary strategies have been implemented to solve this issue, probiotics gained the attention of researchers due to their sustainability. However, it is challenging to ascertain their effectiveness as an extensive range of strains and doses have been reported in the literature. Hence, the objective of this experiment was to perform a meta-analysis of probiotic interventions aiming to reduce ruminal methane emissions from cattle. From 362 articles retrieved from scientific databases, 85 articles were assessed independently by two reviewers, and 20 articles representing 49 comparisons were found eligible for meta-analysis. In each study, data such as mean, SD, and sample sizes of both the control and probiotic intervention groups were extracted. The outcomes of interest were methane emission, methane yield, and methane intensity. For the meta-analysis, effect sizes were pooled using a fixed effect or a random effect model depending on the heterogeneity. Afterward, sensitivity analyses were conducted to confirm the robustness of the findings. Overall pooled standardized mean differences (SMDs) with their confidence intervals (CIs) did not detect significant differences in methane emission (SMD = −0.04; 95% CI = −0.18–0.11; P = 0.632), methane yield (SMD = −0.08; 95% CI = −0.24–0.07; P = 0.291), and methane intensity (SMD = −0.22; 95% CI = −0.50–0.07; P = 0.129) between cattle supplemented with probiotics and the control group. However, subgroup analyses revealed that multiple-strain bacterial probiotics (SMD = −0.36; 95% CI = −0.62 to −0.11; P = 0.005), specifically the combination of bacteria involved in reductive acetogenesis and propionate production (SMD = −0.71; 95% CI = −1.04 to −0.36; P = 0.001), emerged as better interventions. Likewise, crossbreeds (SMD = −0.48; 95% CI = −0.78 to −0.18; P = 0.001) exhibited a more favorable response to the treatments. Furthermore, meta-regression demonstrated that longer periods of supplementation led to significant reductions in methane emissions (P = 0.001), yield (P =