Greenhouse gas, animal performance, and bacterial population structure responses to dietary Monensin to dairy cows

Th e present study investigated the eff ects of a feed additive and rumen microbial modifi er, monensin sodium (monensin), on selected variables in lactating dairy cows. Monensin fed cows (MON, 600 mg d–1) were compared with untreated control cows (CON, 0 mg d–1) with respect to the eff ects of monensin on the production of three greenhouse gases (GHG), methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2), along with animal performance (dry matter intake; DMI), milk production, milk components, plasma urea nitrogen (PUN), milk urea nitrogen (MUN), and the microbial population structure of fresh feces. Measurements of GHG were collected at Days 14 and 60 in an environmental chamber simulating commercial dairy freestall housing conditions. Milk production and DMI measurements were collected twice daily over the 60-d experimental period; milk components, PUN, and MUN were measured on Days 14 and 60. Th e microbial population structure of feces from 6 MON and 6 CON cows was examined on three diff erent occasions (Days 14, 30, and 60). Monensin did not aff ect emissions of methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2). Over a 24-h period, emissions of CH4, N2O, and CO2 decreased in both MON and CON groups. Animal performance and the microbial population structure of the animal fresh waste were also unaff ected for MON vs. CON cows