title: Added dietary sulfur and molybdenum has a greater influence on hepatic copper concentration, intake, and performance in Holstein-Friesian dairy cows offered a grass silage-rather than corn silage-based diet.
abstract: To test the hypothesis that the metabolism of Cu in dairy cows is affected by basal forage and added S and Mo, 56 dairy cows that were 35 (standard error ± 2.2) days postcalving and yielding 38.9 kg of milk/d (standard error ± 0.91) were offered 1 of 4 diets in a 2 × 2 factorial design for a 14-wk period. The 4 diets contained approximately 20 mg of Cu/kg of dry matter (DM), and had a corn silage-to-grass silage ratio of 0.75:0.25 (C) or 0.25:0.75 (G) and were either unsupplemented (-) or supplemented (+) with an additional 2 g of S/kg of DM and 6.5 mg of Mo/kg of DM. We found an interaction between forage source and added S and Mo on DM intake, with cows offered G+ having a 2.1 kg of DM lower intake than those offered G-, but no effect on the corn silage-based diets. Mean milk yield was 38.9 kg/d and we observed an interaction between basal forage and added S and Mo, with yield being decreased in cows offered G+ but increased on C+. No effect of dietary treatment on milk composition or live weight was noted, but body condition was lower in cows fed added S and Mo irrespective of forage source. We found an interaction between forage source and added S and Mo on milk somatic cell count, which was higher in cows offered G+ compared with G-, but not in cows fed the corn silage-based diets, although all values were low (mean values of 1.72, 1.50, 1.39, and 1.67 log10/mL for C-, C+, G-, and G+, respectively). Mean plasma Cu, Fe, and Mn concentrations were 13.8, 41.3, and 0.25 µmol/L, respectively, and were not affected by dietary treatment, whereas plasma Mo was 0.2 µmol/L higher in cows receiving added S and Mo. The addition of dietary S and Mo decreased liver Cu balance over the study period in cows fed either basal forage, but the decrease was considerably greater in cows receiving the grass silage-based diet. Similarly, hepatic Fe decreased more in cows receiving G than C when S and Mo were included in the diet. We concluded that added S and Mo reduces hepatic Cu reserves irrespective of basal forage source, but this decrease is considerably more pronounced in cows receiving grass silage- than corn silage-based rations and is associated with a decrease in intake and milk performance and an increase in milk somatic cell count.
authors.affiliation: Department of Animal Production, Welfare and Veterinary Sciences, Harper Adams University, Edgmond, Newport, Shropshire, United Kingdom TF10 8NB. Electronic address: lsinclair@harper-adams.ac.uk.
authors.forename: L A
authors.initials: LA
authors.lastname: Sinclair
authors.affiliation: Department of Animal Production, Welfare and Veterinary Sciences, Harper Adams University, Edgmond, Newport, Shropshire, United Kingdom TF10 8NB.
authors.forename: D
authors.initials: D
authors.lastname: Johnson
authors.affiliation: Department of Animal Production, Welfare and Veterinary Sciences, Harper Adams University, Edgmond, Newport, Shropshire, United Kingdom TF10 8NB.
authors.forename: S
authors.initials: S
authors.lastname: Wilson
authors.affiliation: Department of Animal Production, Welfare and Veterinary Sciences, Harper Adams University, Edgmond, Newport, Shropshire, United Kingdom TF10 8NB.
authors.forename: A M
authors.initials: AM
authors.lastname: Mackenzie
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D001835:Body Weight; D002417:Cattle; D003300:Copper / Q000008:administration & dosage* / Q000378:metabolism*; D005260:Female; D008099:Liver / Q000378:metabolism*; D008892:Milk / Q000737:chemistry / Q000166:cytology; D008982:Molybdenum / Q000008:administration & dosage*; D006109:Poaceae; D012820:Silage; D013455:Sulfur / Q000008:administration & dosage*; D003313:Zea mays
chemical_list: D013455:Sulfur; D003300:Copper; D008982:Molybdenum
keywords: copper; corn silage; dairy cow; grass silage; liver