title: Monensin for lactating dairy cows grazing mixed-alfalfa pasture and supplemented with partial mixed ration.
abstract: The effect of monensin on milk production was evaluated in 58 lactating Holstein cows (48 multiparous; 10 primiparous) grazing a mixed-alfalfa pasture and supplemented with a partial mixed ration in a completely randomized design with repeated measurements. Cows were paired by calving date, lactation number, previous lactation milk production, body weight, and body condition score and were assigned to one of 2 treatments: control or monensin. Cows on the monensin treatment received 2 monensin controlled-release capsules (335 mg/d for 90 d), one 30 d before the expecting calving date and the other 60 d after calving. Short-term (0 to 150 d in milk) and long-term (305-d adjusted lactation) effects of monensin were evaluated. Pasture (measured by difference between pre- and postgrazing pasture mass), supplements, and total dry matter intake did not differ between treatments and averaged 8.7, 14.1, and 22.9 kg/d, respectively. In the short-term, monensin increased milk production (27.7 vs. 26.6 kg/d) and milk protein yield (0.890 vs. 0.860 kg/d); milk fat yield was not affected (0.959 kg/d). Monensin decreased milk fat content (3.51 vs. 3.60%) with no changes in milk protein content (3.25%). In the long term, milk production and milk protein yield were also increased by monensin: 214 and 7 kg, respectively. Monensin reduced the loss of body condition score and increased percentage of pregnancy at first service (44.8 vs. 20.7%). Monensin improves production and reproduction performance of dairy cows grazing a mixed-alfalfa pasture and supplemented with a partial mixed ration.
authors.affiliation: Estación Experimental INTA Rafaela, Argentina 2300. mgallardo@rafaela.inta.gov.ar
authors.forename: M R
authors.initials: MR
authors.lastname: Gallardo
authors.forename: A R
authors.initials: AR
authors.lastname: Castillo
authors.forename: F
authors.initials: F
authors.lastname: Bargo
authors.forename: A A
authors.initials: AA
authors.lastname: Abdala
authors.forename: M G
authors.initials: MG
authors.lastname: Maciel
authors.forename: H
authors.initials: H
authors.lastname: Perez-Monti
authors.forename: H C
authors.initials: HC
authors.lastname: Castro
authors.forename: M E
authors.initials: ME
authors.lastname: Castelli
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001806:Blood Urea Nitrogen; D001823:Body Composition / Q000187:drug effects; D002417:Cattle / Q000502:physiology*; D004032:Diet; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D007476:Ionophores / Q000008:administration & dosage*; D007774:Lactation / Q000187:drug effects*; D008055:Lipids / Q000032:analysis; D000455:Medicago sativa; D008892:Milk / Q000737:chemistry / Q000187:drug effects; D008894:Milk Proteins / Q000032:analysis; D008985:Monensin / Q000008:administration & dosage*; D011247:Pregnancy; D012098:Reproduction / Q000187:drug effects
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007476:Ionophores; D008055:Lipids; D008894:Milk Proteins; D008985:Monensin