Feeding nanoparticles of copper oxide coated with lysine with or without added antagonists affects the copper status but not the performance of Holstein dairy cows.

The apparent absorption of copper (Cu) in ruminants is low, with between 0.01 and 0.07 g/g absorbed from sources such as copper oxide (CuO) under typical feeding conditions, resulting in high levels of excretion. Improving the bioavailability of Cu could reduce the supplemental amount required to maintain Cu status and reduce excretion, particularly in the presence of dietary antagonists such as sulfur (S) and molybdenum (Mo). The objective of our study was to determine the Cu status of cows when fed nanoparticle CuO coated with Lys compared with conventional CuO when fed without or in combination with antagonists to Cu absorption (S and Mo) in the diet of dairy cows. Fifty-six multiparous Holstein-Friesian cows that were 48 d ± 17.2 (mean ± SD) postcalving and yielding 41 ± 6.4 kg of milk per day were used in a 2 × 2 factorial design. The 4 treatment groups were: CuO (O-), CuO with added antagonists (O+), nano CuO with a lysine coating (N-), and nano CuO with a Lys coating with added antagonists (N+), fed for 16 wk. We formulated the diets to contain ∼17 mg of Cu/kg DM, and diets with antagonists contained an additional 1 g of S/kg DM and 6 mg of Mo/kg DM, with Lys added to O- and O+ to provide the same daily supply as N- and N+. Blood samples were collected at wk 0, 2, 4, 6, 10, and 16, and liver biopsy samples at wk 0 and 16. We found no effect of dietary treatment on DMI, milk yield, live weight, or BCS, with mean values of 23.3 kg/d, 40.1 kg/d, 646 kg, and 2.68, but milk SCC was higher in cows fed conventional compared with nano CuO, or added compared with no added antagonists. We also found no effect of treatment on blood activity of gamma glutamyl transferase, superoxide dismutase, or ceruloplasmin, hematology profile, or plasma Cu and iron concentration. We found that plasma Mo concentration was increased from 0.36 µmol/L in cows fed O- or N- to 0.80 µmol/L in those receiving O+ or N+. Additional dietary antagonists also decreased the concentration of Cu in the liver of cows fed conventional CuO (C+) over the study period by 1.3 mg/kg DM per day, but in cows fed dietary antagonists and nano CuO coated with Lys (N+), liver Cu concentration was increased by 1.1 mg/kg DM per day. Our study is the first to demonstrate that reducing the particle size of CuO into the nano scale with a lysine coating improves the bioavailability of CuO in the presence of dietary antagonists in dairy cattle, and we did not observe any negative effects on performance or health.