title: A field study on the effects of dietary monensin on milk production and milk composition in dairy cows.
abstract: The objectives of this study were to quantify the effect of 16 ppm of dietary monensin on milk production and composition of dairy cows, and to investigate factors having a potential impact on this effect. Data were generated from a total of 3577 Holstein dairy cows (47 herds) in Quebec enrolled in a herd-level, randomized clinical trial investigating the effects of monensin supplementation. Milk production and composition data were collected from monthly dairy herd improvement (DHI) testing. Monensin increased milk production by 0.9 kg/cow/d in cows under 150 days in milk (DIM) (P < 0.05). Monensin decreased milk fat percentage by 0.18 percentage points during the whole lactation (P < 0.05). This decreasing effect was larger for component-fed cows (P < 0.05) and for cows being fed low levels of dietary physically effective particles (P < 0.05) when compared respectively to cows fed total mixed ration and cows fed high levels of dietary physically effective particles. The results of this study suggest that monensin influences milk production and milk composition of dairy cows, and that diet composition and feeding system influence those effects.
authors.affiliation: Département de sciences cliniques, Faculté de médecine vétérinaire, Université de Montréal, C.P. 5000, Saint-Hyacinthe, Québec.
authors.forename: Jocelyn
authors.initials: J
authors.lastname: Dubuc
authors.forename: Denis
authors.initials: D
authors.lastname: DuTremblay
authors.forename: Jean
authors.initials: J
authors.lastname: Baril
authors.forename: Randy
authors.initials: R
authors.lastname: Bagg
authors.forename: Marcel
authors.initials: M
authors.lastname: Brodeur
authors.forename: Todd
authors.initials: T
authors.lastname: Duffield
authors.forename: Luc
authors.initials: L
authors.lastname: DesCôteaux
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003612:Dairying; D019587:Dietary Supplements; D005260:Female; D007476:Ionophores / Q000008:administration & dosage / Q000494:pharmacology*; D007774:Lactation / Q000187:drug effects* / Q000502:physiology; D008055:Lipids / Q000032:analysis; D008892:Milk / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism*; D008985:Monensin / Q000008:administration & dosage / Q000494:pharmacology*; D010316:Particle Size; D011792:Quebec; D011897:Random Allocation
chemical_list: D007476:Ionophores; D008055:Lipids; D008985:Monensin