Comparative Efficacy of Horse and Chicken Serum for the In Vitro Cultivation of Mycoplasma hyorhinis Clinical Isolates

<i>Mycoplasma hyorhinis</i> is an important respiratory pathogen in swine, yet optimal culture conditions for high-yield propagation remain undefined. This study compared horse serum (HS) and chicken serum (CS) at graded concentrations (10%, 20%, 30%) for their ability to support in vitro growth of four clinical <i>M. hyorhinis</i> isolates (strains A, B, C, and D). Cultures were prepared in modified Friis medium, and growth performance was assessed by final titer (color changing unit, CCU/mL) and time-to-detection at 10² and 10⁴ CCU/mL. All media supported growth, but HS consistently outperformed CS in both yield and growth kinetics. The highest titers (10⁹ CCU/mL) and shortest detection times (3.6-6 days) were observed in 20% HS for most strains. Increasing HS concentration to 30% reduced yield for several strains, suggesting a concentration-dependent inhibitory effect. CS demonstrated limited but strain-dependent growth support, with comparable performance to HS for strain B at lower thresholds. These findings identify 20% HS as an optimal supplement for efficient <i>M. hyorhinis</i> cultivation, while highlighting the potential of CS as a cost-effective alternative under certain conditions, with implications for diagnostic reagent production and vaccine development.