Effects of feeding tylosin to layers exposed to Mycoplasma gallisepticum. Poult. Sci

ABSTRACT Two experiments are reported in which the effect of tylosin upon the development of Mycoplasma gallisepticum (MG) infection in replacement layers was monitored by serological and cultural methods. Concentrations of tylosin tested included 0, 22, 38.5, and 55 ppm. Egg pro-duction and feed consumption data were collected for one year. Tylosin slowed the rate of spread of MG infection as measured by serological and cultural meth-ods. The effect of tylosin on the spread of MG infection was dose related. Hen day egg production peaked at 85 to 87 % in the medicated groups, while controls peaked at 81 to 84%. The magnitude of tylosin effect on production increased with time to a maximum difference of 10 to 12 % at 52 weeks. Feed efficiency was markedly improved by all concentrations of tylosin ranging from 5% at peak production to 12 to 18 % at 52 weeks. The incidence of shell-less or soft shelled eggs was markedly reduced in the tylosin treated group