Supplying dairy cows with Propionibacterium to reduce enteric methane emission
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The primary target of this research was to explore the ability of promising propionibacteria strains to reduce the enteric methane emission from dairy cows. The second objective was to study the effect of propionibacteria on ruminal propionate production and the milk production. The objective of our first study was to investigate numerous propionic acid bacteria (most of them are propionibacteria) isolates for their ability to affect the production of methane, volatile fatty acids, and substrate degradation in vitro. Thirty-one strains were screened for the effects on the methane production and volatile fatty acids concentrations in incubated rumen fluid from non-lactating dairy cows. Two strains inoculated showed capability to mitigate methane emission by up to 20% (v/v). Seven strains could promote (P < 0.05) total volatile fatty acids production and five strains stimulated (P < 0.05) the yield of propionate. Seven strains promoted (P < 0.05) the substrate degradation. Propionibacterium thoenii T159 substantially mitigated ruminal methane emission by 20%, and elevated (P < 0.05) overall substrate degradation by 8%. Moreover, this strain elevated total ruminal production of volatile fatty acids by 21%, compared with the control group. From these in vitro results we concluded that Propionibacterium thoenii T159 was the most promising strain to be used in subsequent in vivo studies. The objective of our second study was to determine the ability of Propionibacterium thoenii T159 to establish in the rumen of dairy cows at high feeding level. The strain Propionibacterium thoenii T159 (5 × 10^11 CFU/head × day) was infused into the rumen of four cows via rumen cannula for eight days. After the propionibacteria inoculation ceased, we could still find that three of four donor cows presented substantially increased total population of the propionibacteria (10^6 CFU/mL rumen content) in the rumen as determined by PCR. The present work showed that strain Propionibacterium thoenii T159 was able to persist for at least five days in the rumen of dairy cows at high feed intake. The objective of our third study was to examine the efficacy of the strain Propionibacterium thoenii T159 to mitigate enteric methane emissions, to alter rumen fermentation and to improve the performance of dairy cows in a cyclic change-over design. This study consisted of two subsequent experiments with five intact cows (exp1) and four rumen cannulated cows (exp2). The strain Propionibacterium thoenii T159 (8.5 × 10^11 CFU / head × day) was inoculated into the rumen via esophageal tubing in exp1 and through cannulas in exp2. In both trials the strain Propionibacterium thoenii T159 failed to mitigate enteric methane emission and did not increase milk production. Feed intake, rumen fermentation pattern and digestibility were not, or only negligibly affected by Propionibacterium thoenii T159. In conclusion, the methane mitigation potential of Propionibacterium thoenii T159 shown in vitro, could not be confirmed in vivo.