title: Use of monensin controlled-release capsules to reduce methane emissions and improve milk production of dairy cows offered pasture supplemented with grain.
abstract: We examined the effects of monensin, provided by controlled-release capsules, on the enteric methane emissions and milk production of dairy cows receiving ryegrass pasture and grain. In a grazing experiment, 60 Holstein-Friesian cows were assigned randomly to 1 of 2 groups (control or monensin). Cows in the monensin group received 2 controlled-release capsules, with the second capsule administered 130 d after the first. Milk production was measured for 100 d following insertion of each capsule. The sulfur hexafluoride tracer gas technique was used to measure enteric methane emissions for 4 d starting on d 25 and 81 after insertion of the first capsule, and on d 83 after insertion of the second capsule. All cows grazed together as a single herd on a predominantly ryegrass sward and received 5 kg/d of grain (as-fed basis). In a second experiment, 7 pairs of lactating dairy cows (control and monensin) were used to determine the effects of monensin controlled-release capsules on methane emissions and dry matter intake. Methane emissions were measured on d 75 after capsule insertion by placing cows in respiration chambers for 3 d. Cows received fresh ryegrass pasture harvested daily and 5 kg/d of grain. The release rate of monensin from the capsules used in both experiments was 240 +/- 0.072 mg/d, determined over a 100-d period in ruminally cannulated cows. The monensin dose was calculated to be 12 to 14.5 mg/kg of dry matter intake. There was no effect of monensin on methane production in either the grazing experiment (g/d, g/kg of milk solids) or the chamber experiment (g/d, g/kg of dry matter intake). In the grazing study, there was no effect of monensin on milk yield, but monensin increased milk fat yield by 51.5 g/d and tended to increase milk protein yield by 18.5 g/d. Monensin controlled-release capsules improved the efficiency of milk production of grazing dairy cows by increasing the yield of milk solids. However, a higher dose rate of monensin may be needed to reduce methane emissions from cows grazing pasture.
authors.affiliation: Department of Primary Industries, Ellinbank 3821, Victoria, Australia. chris.grainger@dpi.vic.gov.au
authors.forename: C
authors.initials: C
authors.lastname: Grainger
authors.forename: M J
authors.initials: MJ
authors.lastname: Auldist
authors.forename: T
authors.initials: T
authors.lastname: Clarke
authors.forename: K A
authors.initials: KA
authors.lastname: Beauchemin
authors.forename: S M
authors.initials: SM
authors.lastname: McGinn
authors.forename: M C
authors.initials: MC
authors.lastname: Hannah
authors.forename: R J
authors.initials: RJ
authors.lastname: Eckard
authors.forename: L B
authors.initials: LB
authors.lastname: Lowe
mesh_terms: D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D003692:Delayed-Action Preparations; D004032:Diet; D002523:Edible Grain; D005260:Female; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects; D007774:Lactation / Q000187:drug effects*; D008129:Lolium; D008697:Methane / Q000096:biosynthesis*; D008985:Monensin / Q000008:administration & dosage*
chemical_list: D003692:Delayed-Action Preparations; D008985:Monensin; D008697:Methane