Dependent on the mycoplasma bacteria to be cultivated, the complex media are supplemented with 10-30 % serum and sometimes with yeast extract. Thus, due to the high price of serum the cultivation of mycoplasma bacteria is cost intensive. Further, a reduction of serum in the complex media would be beneficial in light of animal wellfare, too. Thus, there is a need for the cultivation of significant high yields of mycoplasma in a serum-reduced culturing system for the preparation of immunogenic compositions effective in preventing mycoplasma infection. Moreover, the swine specific mycoplasma bacteria are generally cultivated in complex media containing swine specific serum