Location: Dairy Forage ResearchTitle: Effects of ruminal protozoa on methane emissions in ruminants – A meta-analysis
|DAI, XIAOXIA - Royal Veterinary College|
|HUHTANEN, PEKKA - Natural Resources Institute Finland (LUKE)|
|FACIOLA, ANTONIO - University Of Florida|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2022
Publication Date: 8/2/2022
Citation: Dai, X., Kalscheur, K., Huhtanen, P., Faciola, A.P. 2022. Effects of ruminal protozoa on methane emissions in ruminants – A meta-analysis. Journal of Dairy Science. 105(9):7482-7491. https://doi.org/10.3168/jds.2021-21139.
Interpretive Summary: Methane is a potent greenhouse gas produced by ruminants and protozoa can play a critical role in methanogenesis in the rumen. To evaluate the role of protozoa in methanogenesis in ruminants, a meta-analysis was conducted consisting of 64 publications where both ruminal protozoa and methane emissions were measured. There was a positive relationship between ruminal concentration concentration and methane emission. This meta-analysis determined that the concentration of ruminal protozoa explained 13% of the variation in CH4 emission and should be included when calculating methane emissions from ruminants. This research will be of interest to ruminant researchers and nutritionists who are aiming to reduce methane emissions from ruminants while maintaining efficient production of milk and meat from livestock.
Technical Abstract: The effects of ruminal protozoa (RP) concentration on methane (CH4) emissions from ruminants were evaluated in a meta-analysis using 64 publications reporting data from 79 in vivo experiments. Experiments included in the database reported CH4 emissions (g/d) and total RP (TRP, log10 cells/mL) from the same group of animals. The relationship between CH4 emissions and RP (TRP, entodiniomorphids, and isotrichids) and TRP-, entodiniomorphids-, and isotrichids-based CH4 emission prediction models were evaluated as mixed models with experiment as a random effect and weighted by the reciprocal of the SEM and centered around one. There were positive associations between TRP and isotrichids with CH4 emissions but not between entodiniomorphids and CH4 emissions. A reduction in CH4 emissions was observed, averaging 7.96 and 4.25 g/d, per log unit reduction in TRP and isotrichids concentrations, respectively. Total RP and isotrichids were important variables in predicting CH4 emissions from ruminants. Isotrichids CH4 prediction model was more robust than the TRP, evidenciated by lower predicted sigma hat study (%), and error (%), and with higher concordance correlation coefficient. Both TRP and isotrichids models can accurately predict CH4 emissions across different ruminant species, as shown by the low square root of the mean square prediction error (RMSPE), with 6.59 and 4.08% of the mean of RMSPE in the TRP and isotrichids models, respectively. Our results confirm that isotrichids are more important than entodiniomorphids in methanogenesis. Distinguishing these two populations yielded a more robust CH4 prediction model than combining them as total protozoa.