Abstract: 70 of the 45-day Roman chickens were randomly divided into control group and experimental Ⅰ-Ⅵ groups to explore the impact of different doses of Tilmicosin on cardiac function and respiratory. With increasing dose and administration time of Tilmicosin,the results showed that 2 died in Ⅴ group and 4 died in Ⅵ group; heart rate(HR) increased and then gradually restored. However,after 5 h,HR of Ⅵ group was significantly lower than the control group (P＜0.01); left ventricular systolic pressure (LVSP) and maximum rate of change of left ventricular pressure (±dp/dtmax) decreased gradually,the left ventricular end diastolic pressure (LVEDP) is increased gradually. 5 h after administration,LVSP of Ⅳ,Ⅴ and Ⅵ group was significantly lower than the control group,Ⅰ,Ⅱ and Ⅲ group (P＜0.01),Ⅴ and Ⅵ group was significantly lower than group Ⅳ (P＜0.01). LVEDP was significantly higher in group Ⅱ compared with the control group and Ⅰ group (P＜0.05),Ⅲ and Ⅳ were significantly higher than group Ⅱ (P＜0.05),and significantly higher than group Ⅰ (P＜0.01). Ⅴ and Ⅵ group was significantly higher than other groups (P＜0.01); Ⅰ-Ⅴ group breathing gradually deepened and accelerated. After 5 h,the respiration rate of Ⅲ,Ⅳ and Ⅴ were significantly higher than the control group,Ⅰ and Ⅱ group (P＜0.05),but the respiratory rate of Ⅵ group was significantly lower than Ⅲ,Ⅳ and Ⅴ groups (P＜0.01). In the treatment of diseases of chickens,the safe drinking water dose of Tilmicosin is 400-600 mg/L,more than 800 mg/L,has a significant impact on cardiopulmonary function.

Key words: Tilmicosin; chicken; cardiac function; respiratory