The aim of the study was to determine the relationship between the values of the percentage ratio of ammonia nitrogen to urea nitrogen (%N-NH₃:N-CO(NH₂)₂) and other liver function indices and metabolism disorders in cows. The study was carried out in five farms and included 41 dairy cows, both primiparous and multiparous, aged 3-8 years. The average milk production of multiparous cows in previous lactation was 9122 kG milk/305 days. Blood samples for examination were collected twice between 0-30 days after parturition. Concentrations of free fatty acids (FFA), triglycerides (TG), aspartate aminotransferase (AspAT), total cholesterol (Chol), glucose (Glu), urea nitrogen (N-CO(NH₂)₂) in serum and ammonia (NH₃) in plasma were determined. It was discoevered that an increase in AspAT activity (AspAT > 106 IU/L) in serum during the first days after parturition is significantly related to the occurrence of diseases of metabolic origin. Higher values of %N-NH₃:N-CO(NH₂)₂ index (p < 0.05) were in =3 lactations cows with an increased AspAT activity. A significant correlation was observed between %N-NH₃:N-CO(NH₂)₂ and NH₃ (r = 0.76 p<0.001) and N-CO(NH₂)₂ concentrations (r = -0.60 p < 0.001) compared with a lack of relationship between N-CO(NH₂)₂ and NH₃ (r = -0.02 p > 0.05). The ureagenesis disturbances were three times more frequent in older cows (=3 lactation). The cows with an increased AspAT serum activity (>106 IU/L) and %N-NH₃:N-CO(NH₂)₂ index value (>0.73%) demonstrated higher concentrations of NH₃ and lower concentrations of N-CO(NH₂)₂ in the blood (p < 0.05). The obtained results indicate that an increase of %N-NH₃:N-CO(NH(NH₂)₂ coincides with the direction of biochemical blood indice changes characteristic for excessive lipid mobilization. However the evaluation of the ureagenesis disturbances and the dangers of ammonia accumulation in blood is possible only on the basis of NH₃ and N-CO(NH₂)₂ assessment in blood.
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