Abstract
Background:
In high-yielding dairy ewes, metabolic and reproductive processes occurring around the time of parturition and during lactation initiation are accompanied by several changes in blood biochemical parameters, including those related to protein metabolism. However, little is known about the distribution of serum proteins throughout the peripartum period in ewes without higher economic productivity.

Aim:
This study aimed to evaluate changes in serum protein profiles throughout the peripartal period in ewes with milk production only for the nutritional needs of lambs.

Methods:
Twelve clinically healthy ewes of Merino and Cigája crossbreeds at the late stage of pregnancy were included in the study. They were evaluated from 1 mo before the expected lambing to 8 weeks after lambing. Blood samples were collected 4 and 2 weeks before the expected parturition and then 2, 4, 6, and 8 weeks postpartum. The serum samples were analyzed for the concentrations of total serum proteins and the main protein fractions separated by agarose gel electrophoresis.

Results:
Six protein fractions were identified on the serum protein electrophoretogram of the ewes, including albumin, α1-, α2-, β-, γ1 and γ2-globulins. The concentrations of total serum proteins did not significantly vary throughout the evaluated peripartal period, but decreased only slightly around the time of parturition. Significant changes were observed in the relative values and distribution of α1-and γ-globulin fractions (p<0.05 and p<0.01). The absolute albumin concentrations were lowest 4 weeks before lambing and highest in the later postpartal period (p<0.001). The γ1-globulin values showed a significant gradual decrease until 4 weeks after lambing (p<0.05 and p<0.01). Significant changes were observed in the concentrations of γ2-globulins (p<0.01), with the highest values in the later postpartal period similar to γ1-globulins.

Conclusion:
The results suggest that changes in the concentration distribution of serum protein fractions around the time of parturition also occur in ewes with low milk production and may help to better understand the physiological adaptations, which accompany in the female's organism during the transitional period.

Key words: Ewes, Peripartal period, Serum proteins, Electrophoresis, Albumin, Globulins