Efficacy of Propionibacterium strains in mitigating methane emissions from beef heifers fed a high forage diet
The objective of this study was to test the efficacy of Propionibacterium strains to mitigate methane (CH4) emissions in beef heifers fed a high forage diet. Sixteen ruminally cannulated beef heifers were used in a randomized complete block design with 21-d periods. Treatments included: 1) Control, 2) Propionibacterium freudenreichii T114, 3) P. thoenii T159, and 4) P. freudenreichii T54. Strains (10 × 1011 CFU) were administered daily directly into the rumen prior to feeding. All heifers were fed a basal diet consisting of 60:40 barley silage:barley grain. Environmental chambers were used for CH4 measurements. No treatment effects were observed for overall DMI (P = 0.76) or DMI in chambers (P = 0.67). Mean ruminal pH averaged 6.17 and was not affected by treatments (P = 0.62). Likewise, both minimum and maximum ruminal pH were similar for all treatments (P > 0.10). No treatment differences were observed for total VFA (P = 0.44) or ammonia-N concentration (P = 0.79). However, proportions of individual VFA changed with acetate being reduced with Propionibacterium T159 (61.1 vs 63.8; P = 0.02), whereas ruminal isobutyrate (1.18 vs 1.00; P < 0.01) and acetate:propionate ratio (3.95 vs 3.40; P = 0.04) were greater with Propionibacterium T114, relative to the Control. Total daily enteric CH4 production averaged 188 g/d and was not affected by Propionibacterium strains (P = 0.57). Enteric CH4 emission intensity averaged 22 g/kg of DMI and was numerically greater with Propionibacterium T114; however, treatment effects were not significant (P = 0.19). In conclusion, Propionibacterium strains, T159 and T54, did not affect total enteric CH4 production possibly due to their inability to increase ruminal propionate concentrations. On the contrary, Propionibacterium T114 numerically increased CH4 emission intensity and the effects could be attributed to greater acetate:propionate ratio observed with the inoculated strain.
Keywords: beef, methane, Propionibacterium