Monensin supplementation effects on methane output and behavior of late lactation Holstein cows

Multiple strategies have been tested in the attempt to reduce enteric methane (CH 4 ) emissions and yield from dairy cattle.Among them, supplementation with monensin.Behavioral change strategies are often adopted by dairy cows to adapt to environmental changes.In the present study, 20 cows were supplemented with either 300 mg/cow/d of monensin in 34 g/cow/d of dried distillers grains (MON, n = 10) or only DDG (CON, n = 10), both top-dressed on TMR.Automated monitoring devices (Nedap, Groenlo, Netherlands) were used to assess behavioral activity of late lactation cows supplemented with monensin (MON; n = 5) or non-supplemented (CON; n = 5).Cows received a leg tag to measure daily lying time, number of steps and standing bouts and a neck tag to measure eating and rumination time.Behavioral activities were recorded for 21 d before supplementation began and for 28 d during supplementation.Cows were housed in a sand-bedded freestall barn with Calan gates and equipped with a cooling system including shade, fans and soakers.A GreenFeed system was used to measure enteric gas output.Daily CH 4 emissions and yield were significantly reduced with monensin.No differences in behavioral activities were observed between MON and CON during the 21-d period before monensin supplementation.During the 28 d of monensin supplementation, daily eating time did not differ between MON and CON.Rumination and lying times were greater in MON compared with CON.Non-supplemented cows (CON) tended to be more inactive, had more steps per day and spent more time standing compared with MON cows.No differences between MON and CON cows were observed in standing bouts per day.The present results suggest that monensin reduces daily enteric CH 4 emissions and yield and monensin supplementation is associated with positive behavioral changes in late lactation dairy cows.