The analysis of the protein spectrum of blood was carried out by electrophoresis in agarose gel in combination with the determination of biochemical parameters in 30 stallions of the Arabian breed, divided into groups according to the indicator of progressive sperm mobility. Group 1 included stallions with progressive mobility (PM) up to the 25th percentile (PM, % <53.35), group 2 - stallions with progressive mobility within the 25-75th percentile (53.35 <PM, % <65.18), and group 3 - stallions with progressive mobility above the 75th percentile (PM, %> 65.18). In the 1st group of stallions, the highest concentrations of α2-globulins and γ-globulins of blood were found. The 3rd group of stallions showed the lowest concentration of glucose and urea.

Studies were conducted to assess the elemental composition of the blood serum of 39 Arabian pure breed stud horses. The correlation between the content of toxic elements in the blood serum: aluminum (Al), arsenic (As), cadmium (Cd), lead (Pb), tin (Sn), mercury (Hg), essential trace elements: cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), iodine (I), manganese (Mn), selenium (Se), zinc (Zn) and macronutrients: calcium (Ca), potassium (K), magnesium (Mg), phosphorus (P) was studied. A negative correlation was established between the content of mercury and iron in the blood serum of stud horses (r=-0.34; p=0.04). A negative correlation was also found between the levels of cadmium and calcium in the blood serum (r=-0.40; p=0.02). The establishment of these correlations suggests the presence of competitive relations between these elements in the body of horses. Positive correlations were established between the content of toxic elements in the blood serum: Al/As (r=0.38; p=0.02), Al/Pb (r=0.41; p=0.009), Al/Sn (r=0.56; p=0.002), As/Sn (r=0.46; p=0.0003), Pb/Sn (r=0.32; p=0.05).