Shahid Bahonar University of Kerman and Iranian Society of Animal Science Journal of Livestock Science and Technologies 2322-3553 14 2 2026 02 01 Effects of different copper supplement sources on growth performance, nutrient digestibility, and blood parameters in Holstein suckling calves 57 65 5055 10.22103/jlst.2025.25468.1641 EN Yadollah Chashnidel Department of Animal Nutrition, Faculty of Animal Sciences and Fisheries, Sari University of Agricultural Sciences and Natural Resources, Sari, Iran Radman Bakhtiari Department of Animal Nutrition, Faculty of Animal Sciences and Fisheries, Sari University of Agricultural Sciences and Natural Resources, Sari, Iran Hamid Reza Mardani Department of Chemistry, Payame Noor University (PNU), PO BOX 19395‑3697 Tehran, Iran Journal Article 2025 06 26 To evaluate the effects of copper (Cu) supplement source on Holstein suckling calves, 40 newborn male calves (mean birth weight: 39.6±2.4 kg) were randomly assigned to a completely randomized design for 70 days. The four experimental treatments consisted of the basal diet (7.89 mg Cu/kg dry matter) supplemented with 10 mg Cu/kg dry matter from different copper sources: Cu-acetate (27% purity), Cu-chloride (36% purity), Cu-sulfate (23% purity), and Cu-tribasic (58% purity). Calf body weight (BW) was measured weekly, while starter intake was recorded daily. Apparent digestibility was assessed using acid-insoluble ash as an internal marker. Blood samples were drawn from the jugular vein at the end of the trial. Final BW, total weight gain, and average daily gain were significantly greater in calves fed Cu-acetate and Cu-sulfate compared to those receiving Cu-chloride and Cu-tribasic (P<0.01). Dry matter digestibility was significantly enhanced in calves fed Cu-acetate compared to the other experimental treatments (P<0.01). Apparent digestibility of ether extract (P<0.01) and acid detergent fiber (P<0.05) was greater in calves fed Cu-acetate than in those fed Cu-chloride or Cu-tribasic. Plasma globulin concentration was significantly greater in calves fed Cu-tribasic compared to those receiving Cu-acetate and Cu-chloride (P<0.05). Plasma cholesterol levels were significantly higher in the Cu-sulfate group than in the other treatments (P<0.05). The concentration of low-density lipoprotein was significantly lower in the Cu-acetate group compared to other treatments (P<0.05). Plasma zinc levels were significantly increased in calves receiving Cu-chloride compared to other groups (P<0.01). Plasma aspartate aminotransferase activity was significantly greater in calves fed Cu-acetate compared to those receiving Cu-chloride or Cu-tribasic (P<0.01). It was concluded that adding 10 mg Cu/kg dry matter to the basal diet through Cu-acetate and Cu-sulfate supplements had a more favorable effect on the growth performance in Holstein suckling calves compared to Cu-chloride and Cu-tribasic salts. https://lst.uk.ac.ir/article_5055_069cf420e523a7f3a547bbea13929ce4.pdf