Does the methanogenesis inhibitor 3-nitrooxypropanol affect milk yield in dairy cattle?

PICO Question In dairy cattle, does the methanogenesis inhibitor 3-nitrooxypropanol affect milk yield, compared to cows that receive no intervention to reduce enteric methane emissions? Clinical bottom line Category of research Treatment. Number and type of study designs reviewed A total of 15 controlled trials were critically reviewed, of which 11 were randomised. Strength of evidence Moderate. Outcomes reported Eleven studies reported no effect of 3-nitrooxypropanol (3-NOP) on milk yield at doses ranging from 40 to 135 mg of 3-nitrooxypropanol/kg of feed dry matter (DM). Two studies reported trends for decreased milk yield at doses greater or equal to 80 mg of 3-NOP/kg of feed DM, while a further two studies reported statistically significant declines in milk yield at doses of 80 mg of 3-NOP/kg of feed DM. Conclusion The reviewed studies provide a moderate strength of evidence to support that the administration of the methanogenesis inhibitor 3-NOP at concentrations less than 80 mg/kg of feed DM does not significantly affect milk yield in dairy cattle. Some studies suggest that 3-NOP may adversely affect milk yield at higher doses but the results are inconsistent.