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The effects of lactation stages and anticoagulants on the ceruloplasmin (Cp) activity were investigated in 240 Holstein dairy cows. The cows were classified according to their lactation stages into four different groups as close-up stage (3–1 week(s) antepartum), fresh-lactation stage (0–1 week postpartum), early-lactation stage (3–5 weeks postpartum), and mid-lactation stage (15–18 weeks postpartum). Each group consisted of 60 multiparous cows. Serum and plasma samples (heparin and EDTA) were obtained from each cow. The activity of ceruloplasmin was measured by p-phenylenediamine oxidation. Cp activity was higher in the group of fresh-lactation stage than other groups (P < 0.05). Pooled data of the four groups revealed higher Cp activities in heparinized plasma than serum and EDTA plasma and in serum than EDTA plasma (P < 0.05). Cp activities in serum and EDTA plasma were approximately 30% and 57%, respectively, lower relative to heparinized plasma. High correlation was found between heparinized plasma Cp and serum Cp (r = 0.82; P < 0.000). Suggestive reference values for serum Cp and heparinized plasma Cp were 88–334 and 143–459 mg/l, respectively. Ceruloplasmin undergoes a physiological increase just after calving and it is recommended to use heparinized plasma for estimation of ceruloplasmin in Holstein dairy cows.