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Previous studies demonstrated that protein content in boar seminal plasma were highly correlated with fertility of boars. The purpose of the present study was to determine if protein content in seminal plasma significantlyvaries betweenboars, as well as if season of the year, boar breed or age significantly influence protein content in seminal plasma. In the first experiment, semen was collected weekly for 12 months, from 4 boars (48 ejaculates per boar). In the second experiment, two ejaculate per boars were taken from 106 boars (total 212 ejaculates) at commercial pig farm in Serbia. Total protein content in seminal plasma was determined for each collection. Protein content in seminal plasma considerably varies between individual boars (from 1.5% to 4.6%). More than 50% of boars had less than 3% protein in the seminal plasma. Protein content in seminal plasma is quite constant in the ejaculates of the same boar, at the one ejaculate per week collection frequency condition, with very little variations between months during the year. Boar breed or age did not have a significant (P>0.05) impact on the protein content in seminal plasma (Landrace=2.98%; Large White=2.92% and Duroc=3.01%; ���16 months=3.04%, 17 to 20 months=3.14%, 21 to 24 months=3.03 and ��� 25 months=2.74%). These data indicated that the seminal plasma protein content could be genetically determined for each single boar. Consequently, these findings support the assumption that quantification of protein content in seminal plasma could serve as a powerful tool to improve boar fertility and reproductive performance.