Effect of inorganic or organic copper fed without or with added sulfur and molybdenum on the performance, indicators of copper status, and hepatic mRNA in dairy cows

The effect of inorganic (INORG) or organic (ORG) Cu, fed without (−) or with (+) additional S and Mo on Cu status and performance was examined using 56 early lactation dairy cows in a 2 × 2 factorial study design. Supplementary Cu was added as either CuSO4 or BioplexCu (Alltech Inc., Nicholasville, KY) to provide an additional 10 mg of Cu/kg of dry matter (DM), with S added at 1.5 g/kg of DM and Mo at 6.8 mg/kg of DM to reduce Cu bioavailability. The basal ration was composed of corn and grass silages (2:1 respectively, DM basis) and straight feeds. Cows commenced the study at wk 7 of lactation and remained on treatment for 16 wk. An interaction existed between Cu source and added S and Mo on DM intake, with cows offered INORG− Cu having an increased intake compared with those offered INORG+ or ORG− Cu. Milk yield averaged 35.4 kg/d, and was 5% higher with milk fat content 6% lower in cows fed INORG compared with ORG Cu, but milk fat yield, energy-corrected milk yield, and milk protein content did not differ between treatments. A trend existed for cows to have a higher body weight gain when offered ORG compared with INORG Cu. Cows fed diets containing INORG Cu had a higher milk concentration of C17:0 and C18:3n-3 compared with those fed diets containing ORG Cu. Cows fed added S and Mo had a lower milk concentration of C17:0 and C18:0 compared with those that were not supplemented. No effect was observed of dietary treatment on plasma Cu concentration, which averaged 13.1 µmol/L, except during wk 12 when cows receiving added S and Mo had a lower concentration. No effect was observed of Cu source on mean plasma Mo concentrations, but during wk 16 cows offered INORG Cu had a higher concentration than those offered ORG Cu. Hepatic Cu levels decreased by approximately 0.9 mg/kg of DM per day when fed additional S and Mo, but no effect of Cu source was observed. A trend existed for hepatic ATPase, Cu++ transporting, beta polypeptide (ATP7B) to be upregulated in cows when fed S and Mo along with ORG but not INORG Cu. In conclusion, the inclusion of an ORG compared with an INORG source of Cu reduced milk yield but increased milk fat concentration and body weight gain, with no effect on energy-corrected milk yield. Little effect was observed of dietary Cu supply on plasma mineral concentration, liver mRNA abundance, or milk fatty acid profile, whereas the addition of S and Mo reduced hepatic Cu concentrations.