Changes of acute-phase proteins during different phases of the estrous cycle in Ovsynch-synchronized Holstein cows

Background: Acute-phase proteins (APPs) may be increased due to different stresses during estrus phase in farm animals. Aims: Determining changes of APPs at different phases of non-synchronized estrous cycle group (NSEG), and Ovsynch-synchronized estrous cycle group (SEG) in Holstein cows. Methods: Twelve non-pregnant clinically and paraclinicaly healthy Holstein cows with a body condition score (BCS) of 2.75 and 70 days in milk were chosen. Two groups including NSEG and SEG were performed. Blood sampling was carried out from NSEG at the time of diestrus, proestrus, and estrus. In SEG, blood sampling was performed on day 7 (at the time of prostaglandin injection, equivalent diestrus), day 9 (at the time of gonadotropin-releasing hormone (GnRH) injection, equivalent proestrus), and day 10 (at the time of insemination, equivalent estrus) of synchronization protocol. Concentrations of haptoglobin (Hp), serum amyloid A (SAA), ceruloplasmin (Cp), and fibrinogen (Fib) were measured. Results: Concentration of Hp at estrus phase was significantly higher compared with diestrus (P=0.001) and proestrus (P=0.019) in NSEG. Moreover, Hp level in the NSEG was significantly higher than SEG at estrus phase (P=0.002). Concentrations of SAA, Cp, and Fib had no significant differences during various phases of estrous cycle in each group or between equivalent phases of both groups. Conclusion: It seems that unlike SAA, Fib, and Cp, concentrations of Hp may be affected by different phases of estrous cycle. Although APPs are not specific indicators, their changes besides other clinical and paraclinical indices may be helpful for more accurate heat detection in dairy cows.