Effect of tylosin in the feed of broiler breeder birds on their serological reaction to Mycoplasma synoviae.

Serum plate (SP) reactions and geometric mean Mycoplasma synoviae (MS) hemagglutination-inhibition (HI) titers were determined on sera from broiler breeder hens fed either 50 g tylosin per ton of feed or 150 g tylosin per ton of feed for 4 weeks before and 4 weeks after MS exposure by aerosol. Then tylosin was increased to 150 g per ton of feed and 300 g per ton of feed, respectively, for 8 weeks. One group of birds, without tylosin in the feed, was exposed to MS by aerosol. One group of birds received no tylosin in the feed and were not exposed to MS. Sera from MS exposed birds with tylosin in the feed up to 300 g per ton of feed did not show any difference in the MS SP reactions or MS HI titers when compared with MS exposed birds without tylosin in the feed. Tylosin in the feed up to 300 g per ton did not mask any MS SP reactions nor did tylosin cause any MS SP positive or HI positive birds to appear serologically negative.