摘要:Managing and determination of the blood lipid profile and oxidative status are useful tool to show the influence
of foreign chemical substances on production of dairy cows. Investigation of various biomarkers of
oxidative stress related to various problems in the production dairy cows presents a very important issue. The
aim of this research was to investigate different biological markers in two different breeds of dairy cows - the
Holstein Friesian and the Simmental, during different stages of lactation. The total of 60 Holstein Friesian and
Simmental cows were divided into two treatments (HF and S) which was further divided into three groups
each, respectively. Lactating groups of each cow breed was divided into three stages at early lactation of
32-75 days (HF1 and S1), peak lactation of 80-165 days (HF2 and S2) and low lactation of 175 days onward
(HF3 and S3). During the research the total milk production and the percentage of milk fat and protein were
determined. Blood samples were collected from jugular vein of each cow, the serum was harvested without
anticoagulant and stored at -20 °C in small aliquots till further analysis. Serum was then analyzed for triglyceride,
cholesterol, HDL, LDL, AST, ALT, GGT, the total antioxidant status (TAS), the total oxidant status (TOS),
MDA, SOD, catalase and paraoxonase (PON1). Significantly (P<0.05) higher values of cholesterol, TOS and
SOD at peak lactation stage was observed in all cows. A gradual decline from early lactation to low lactation
was observed in the values of triglycerides and ALT, while MDA gradually increased from the same stage in
all cows. The values of LDL and catalase showed an irregular pattern of variations in various lactation stages
among all groups. The Holstein Friesian breed showed significantly higher values of ALT and PON1, while values
of HDL, TAS and TOS were the lowest in Simmental group (P<0.05). By measuring the signs of oxidative
stress, it was concluded that metabolic efforts of cows during the peak of lactation affected the investigated
parameters. Disturbance in feed intake and rise in metabolic processes lift up oxidative stress in cows, especially
during the peak of lactation, which might be determined by monitoring blood alterations. Results of our
study indicated that the Holstein Friesian breed was under higher oxidative stress during different lactation
stages compared to Simmental dairy cows.