The effects of dietary medium‐chain fatty acids on ruminal methanogenesis and fermentation in vitro and in vivo: A meta‐analysis

Abstract

The efficacy of methane (CH 4 ) suppression using medium-chain fatty acids (MCFA) remains inconclusive, despite a number of studies on this topic are available. We thus carried out a meta-analysis to integrate the published data on different concentrations and types of MCFA such as lauric acid and myristic acid, which investigated ruminal methanogenesis and fermentation in in vitro and in vivo experiments. In vitro MCFA sources were classified either as pure MCFA (lauric acid, myristic acid and their combinations) or as natural MCFA-rich oils (canola oil enriched with lauric acids, coconut oil, krabok oil and palm kernel oil). The MCFA sources used in the in vivo studies were coconut oil, lauric acid, myristic acid and the combination of lauric and myristic acids. A total of 41 studies (20 in vitro and 21 in vivo studies) were compiled in our database, which included the data on CH 4 emission, digestibility, ruminal fermentation products and microbial populations. The results showed that the amount of CH 4 production per unit of digested organic matter decreased linearly under in vitro conditions (p < .01) and tended to decrease quadratically under in vivo conditions (p < .07) with increasing doses of MCFA. Populations of protozoa (p < .01) in both in vitro and in vivo responded negatively in a linear manner, whereas Archaea population diminished quadratically (p = .04) only in the in vitro conditions with increasing doses of MCFA. Increasing dietary MCFA concentrations also reduced the fibre digestibility linearly (p < .05) in both in vitro and in vivo conditions. CH 4 production for different sources of MCFA decreased in following order: coconut oil > lauric acid > myristic acid > mixed lauric and myristic acids > palm kernel oil > canola oil enriched with lauric acids > krabok oil. It can be concluded that the effect of MCFA on ruminal methanogenesis depends on the amount and type of MCFA.

The Utilisation of Tannin Extract as a Dietary Additive in Ruminant Nutrition: A Meta-Analysis

“…Another beneficial effect is the toxic effect of tannin that could diminish undesirable ruminal microorganisms involved in methane formation, resulting in lower methane production [ 7 ]. Nonetheless, due to the presence of other bioactive molecules in the whole plant that might interfere with the tannin effect such as phenolic acid, flavonoids, diterpenes [ 83 , 84 ], saponins [ 85 ], lipids [ 9 ], and essential oils [ 86 ], studies regarding the effect of tannin on ruminants have been moving forward to specifically determine the influence of tannin in extracted or purified form on ruminant methane production, digestibility, and performance [ 87 , 88 ]. It is expected that the effects of extracted tannin on those parameters would be more obvious corresponding to the type of tannin used, i.e., CT and HT.…”

“…The database was analysed by employing the mixed model methodology [ 79 , 80 ], using the MIXED procedure of SAS software (version 9.2, SAS Institute Inc., 2008). Different experiments were considered as random effects and tannin-related factors (either concentration or type of tannin) were treated as fixed effects, followed Jayanegara et al [ 12 ] and Yanza et al [ 9 ] with some modifications. The assessment of the tannin extract supplementation level and tannin type (CT or HT) was accomplished with the following statistical model: Y ij = µ + s i + τ j + sτ ij + B 0 + B 1 X ij + B 2 X 2 ij + b i X ij + e ij where Y ij = dependent variable, µ = overall mean, s i = random effect of the - i th experiment, τ j = fixed effect of the - j th level of factor τ , sτ ij = random interaction between the - i th experiment and the - j th level of factor τ , B 0 = overall intercept across all experiments (fixed effect), B 1 = linear regression coefficient of Y on X (fixed effect), X ij = value of the continuous predictor variable (tannin extract level), b i = random effect of study on the regression coefficient of Y on X in study - i , and e ij = the unexplained residual error.…”

“…The RANDOM statement was declared based on different studies included. The number of replicates in the studies was declared in the WEIGHT statement available in SAS as performed by Jayanegara et al [ 12 ] and Yanza et al [ 9 ]. The model was considered significant at p ≤ 0.05 or tends when the p -value was >0.05 and ≤0.10.…”

“…Another beneficial effect of tannin is its ability to decrease enteric methane emissions [ 7 ]. Enteric methane emissions are an important issue to consider since ruminants contribute to approximately 17% of global methane emissions or about 47% of the global livestock sector for global greenhouse gases [ 8 , 9 ]. A number of experiments have demonstrated the methane-mitigating property of tannin.…”

Effect of dietary tannins on the performance, lymphoid organ weight, and amino acid ileal digestibility of broiler chickens: A meta-analysis

“…Data with compatible measurement units were processed for statistical analysis using a mixed model procedure for meta-analysis [ 35 , 36 , 37 ]. The analysis was run with SAS version 9.1 using the PROC MIXED procedure.…”