The effect of cyadox and virginiamycin on Marek's disease in chickens

Chickens infected with highly virulent Marek's disease virus were administered in the course of 56-day fattening cyadox at a dose of 20 mg per kg feed mixture (MC group). and virginiamycin at a dose of 10 mg per kg feed mixture (MV group). The weight gains on the 56th day and dressing percentage were highest, in comparison with the control group (711.11 g and 60.62%), in the virginiamycin-treated group. An investigation into the basic chemical composition of meat revealed lower contents of dry matter and proteins in the virginiamycin-treated group (26.9% and 22.76%) if compared with the control group of chickens which were also infected with Marek's disease virus. A biometrical examination of the organs showed a statistically significant decrease in heart weight in the cyadox-treated group, increase in liver and heart weight and intestine shortening in the virginiamycin-treated group, in comparison with the control group. Pathologico-anatomical changes typical of Marek's disease were recorded in a randomly selected number of chickens in 33.3% in the control group, in 28.5% in the cyadox-treated group and in 50.0% in the virginiamycin-treated group.