The invention relates to the use of at least one acid stable protease in poultry feed in combination with anti-coccidial vaccination of birds for increasing the performance of vaccinated animals. It has been found surprisingly that the additions of at least one acid stable protease according to the invention to the diet of “cocci”-vaccinated birds have a significant improvement of animal performance. The inventors found that especially the use of serin proteases improve the performance of vaccinated broiler chickens, in particular the use of serin proteases increases weight gain and improves Feed Conversion Ratio (FCR) of cocci-vaccinated birds.
