Rapid Communication: Evaluation of methane inhibitor 3-nitrooxypropanol and monensin in a high-grain diet using the rumen simulation technique (Rusitec)
Rapid Communication: Evaluation of methane inhibitor 3-nitrooxypropanol and monensin in a high-grain diet using the rumen simulation technique (Rusitec).
J Anim Sci. 2017 Sep;95(9):4072-4077. doi: 10.2527/jas2017.1896.
Plain language summary
Research on the use of enzymatic inhibitors to decrease enteric methane (CH4) production has regained popularity with the development of 3-nitrooxypropanol (NOP), a synthetic compound that inhibits the last step of methanogenesis. Since then, NOP has been evaluated in diverse conditions using different animal species and doses. However, little is known about the combined effects of NOP and other mitigation strategies on CH4 production. The objective of the study was to evaluate NOP, the ionophore monensin and their combination on CH4 production. The study was conducted using a rumen simulation technique. We concluded that the combined effects of NOP and MON on CH4 mitigation did not exceed the effect of NOP alone.
© 2017 American Society of Animal Science. All rights reserved. The objective of this study was to evaluate the effects of 3-nitrooxypropanol (NOP), a known methane (CH4) inhibitor; the ionophore monensin (MON); and their combination on in vitro CH4 production in a high-grain diet (85% barley grain, 10% barley silage, and 5% vitamin-mineral supplement; DM basis) using a rumen simulation technique (Rusitec). Sixteen fermentation vessels in 2 Rusitec apparatuses (blocks) were used in a completely randomized block design with 4 treatments: Control, NOP (200 µg/g DM), MON (200 µg/g DM), and the combination of 200 µg NOP/g DM and 200 µg MON/g DM (NOP + MON). Two fermenters within each apparatus were randomly assigned to a treatment. Treatments were mixed with 10 g of substrate and supplied on a daily basis. The study included an 8-d adaptation period without treatment supplementation and a 6-d period for addition of treatments. Dry matter disappearance, pH, and total VFA were not affected by treatment (P ≥ 0.34). Acetate proportion was decreased by 8.3% and 14.9% with NOP and NOP + MON (P < 0.01), respectively; however, propionate proportion was not affected by treatment (P = 0.44). The acetate to propionate ratio was lowered by 21.1% with the combination of NOP and MON (P = 0.02), whereas ammonia-N concentration was not affected by treatment (P = 0.50). Total gas production was unaffected (P = 0.50), but CH4 production decreased by 77.7% and 75.95% (P < 0.01) with NOP and NOP + MON addition, respectively. Concurrently, H2 gas production increased by 131.3% and 185.6% (P = 0.01) with NOP and NOP + MON treatments, respectively. The copy number of methanogens was decreased in both solid and liquid phases (P < 0.01) with NOP and NOP + MON treatments. Despite the combination of NOP + MON showing the greatest decrease in acetate molar proportion and acetate to propionate ratio, it did not further inhibit CH4 beyond the effect of NOP alone. The decrease in CH4 emissions with treatments that included NOP occurred along with a decrease in the copy number of methanogens associated with the solid and liquid phases, confirming the inhibitory effects of NOP on these microorganisms. In conclusion, the combined effects of NOP and MON on CH4 mitigation did not exceed the effect of NOP alone when using a high-grain diet in vitro.