Dietary treatment with omega fatty acids mediates in vitro rumen fermentation kinetics and reduce methane emission in water buffalo

Purpose: To investigate the effect of dietary supplementation of two omega fatty acids on in vitro rumen fermentation, microbial populations, total gas and methane (CH4) production. Methods: Both linoleic and linolenic acids were supplemented at 0 (control), 1, 3, 5 and 7 % of dry matter (DM) in a ration with a high roughage to concentrate ratio (70: 30). Total gas and CH4 were measured at 3, 6, 9, 12 and 24 h of fermentation while pH, volatile fatty acids (VFA), and ammonia nitrogen (NH3-N) concentrations were measured at 24 h using buffalo rumen fluid in an in vitro batch culture system. Microbial populations were determined using 16S-rDNA gene primers by RT-PCR. Results: The results revealed that linoleic acid at 3, 5 and 7 % decreased the concentration of NH3-N (p < 0.05) but linolenic acid at 5 and 7 % increased NH3-N (p < 0.05). A linear decrease (p <0.001) in acetate and butyrate, coupled with linear increase (p <0.001) in propionate was observed in response to treatment. Furthermore, supplementation of 3, 5 and 7 % of both fatty acids linearly (p < 0.001) decreased total gas and CH4 production when compared to the control. The addition of linoleic acid linearly (p < 0.001) decreased the number of protozoa without affecting methanogens, while linolenic acid linearly and quadratically (p < 0.001) reduced the population of both protozoa and methanogens (p < 0.05). Conclusion: Linolenic acid is more effective at a 3 % level in reducing methane production (up to 63 %) in high roughage diets.

Automated summary

The study investigated the effects of dietary supplementation of two omega fatty acids on in vitro rumen fermentation, microbial populations, total gas, and methane production. Results showed that linolenic acid at 3% level was most effective in reducing methane production in high roughage diets.