title: Effect of monensin on milk production of Holstein-Friesian dairy cows.
abstract: We examined the effects of monensin on feed intake and milk production in Holstein-Friesian cows receiving a total mixed rations in two experiments. In experiment 1, 60 individually fed cows consumed, during wk 7 to 26 of lactation, 1 kg/d of supplement containing either 0, 150,300, or 450 mg of monensin. In experiment 2, 98 group-fed cows also received 1 kg/d of a supplement with either 0 or 300 mg/d of monensin for two consecutive lactations. In lactations 1 and 2, treatment started at wk 8 and 3 wk prior to calving, and continued for 32 wk. In experiment 1, 150, 300, and 450 mg of monensin/d produced a small decrease in feed intake and milk yield responses of 2.8, 2.5 and 1.5 kg/d, respectively. In experiment 2, milk yield responses of 0.8 and 1.1 kg/d were recorded in lactations 1 and 2. Milk fat and milk protein content declined in experiments 1 and 2, lactations 1 and 2 by 0.46, 0.38 and 0.27%, and 0.16, 0.16 and 0.11%, respectively. Yield of milk constituents was unaffected. Efficiency of milk production was increased by 5% in experiment 1. In experiment 2, lactation 2, monensin decreased beta-hydroxybutyrate and acetoacetate but increased blood glucose concentration.
authors.affiliation: Centre for Dairy Research, Department of Agriculture, The University of Reading, Arborfield, UK. r.h.phipps@reading.ac.uk
authors.forename: R H
authors.initials: RH
authors.lastname: Phipps
authors.forename: J I
authors.initials: JI
authors.lastname: Wilkinson
authors.forename: L J
authors.initials: LJ
authors.lastname: Jonker
authors.forename: M
authors.initials: M
authors.lastname: Tarrant
authors.forename: A K
authors.initials: AK
authors.lastname: Jones
authors.forename: A
authors.initials: A
authors.lastname: Hodge
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000097:blood; D000090:Acetoacetates / Q000097:blood; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects; D002417:Cattle / Q000502:physiology*; D002149:Energy Intake; D005223:Fats / Q000032:analysis; D005260:Female; D007476:Ionophores / Q000008:administration & dosage / Q000494:pharmacology*; D007774:Lactation / Q000187:drug effects* / Q000502:physiology; D008892:Milk / Q000737:chemistry; D008894:Milk Proteins / Q000032:analysis; D008985:Monensin / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D000090:Acetoacetates; D001786:Blood Glucose; D005223:Fats; D007476:Ionophores; D008894:Milk Proteins; D008985:Monensin; D020155:3-Hydroxybutyric Acid