Compatibility of a combination of tiamulin and chlortetracycline with salinomycin in feed during a pulsed medication...

In an earlier study, the continuous medication of broiler feed with a combination of tiamulin (TIA; 20 mg/kg), chlortetracycline (CTC; 60 mg/kg), and the ionophore anticoccidial salinomycin (SAL; 60 mg/kg) caused an initial increase in BW and feed efficiency (FE; g of weight gain/kg of feed intake). However, as doses increased to combinations of 30 mg/kg of TIA and 90 mg/kg of CTC or 50 mg/kg of TIA and 150 mg/kg of CTC, there was a dose-related reduction in growth rate and FE. This was thought to be due to the interaction between TIA and SAL. In this study, using a protocol similar to the previous trial, broiler chicks were administered SAL at 60 mg/kg via the feed and the same inclusion rates of TIA + CTC. However, instead of feeding the birds continuously, considering the cost of TIA and possibly to compensate for the depressed growth attributable to the interaction with SAL, they were pulse-dosed for 1 to 10 d and again at 21 to 27 d, and the whole trial lasted 35 d to see if the intermittent pulses might reduce production losses. A total of 200 straight-run 1-d-old broiler chicks (Hubbard classic) were randomly distributed into 4 groups, with each group consisting of 5 cages containing 10 birds. The 20 cages were allocated to the 4 treatment groups on a random basis. The control diet, containing only SAL at 60 mg/kg, was fed to all birds throughout the 35-d trial, including the period during the gaps between dosing (i.e., d 11 to 20 and d 28 to 35). Feed and water were available for the whole trial period. Several serum enzymes (creatine kinase, lactate dehydrogenase, and aspartate aminotransferase) were determined from blood samples taken on d 35. Blood samples were also collected at 1, 19, and 35 d of age and were examined for antibody titers to Mycoplasma gallisepticum and Mycoplasma synoviae. Necropsy and histopathology of the birds (n = >or=4) were conducted during weekly intervals. There was no significant difference in weight gain, feed intake, and FE when the groups treated with TIA + CTC were compared with the control group (P > 0.05). There was no relationship between mortality and inclusion rates of the medication. No clinical signs of an interaction were exhibited during the trial, which was supported by necropsy and serum enzyme results. Maternally derived antibodies against M. gallisepticum were identified at the start of the trial but disappeared within 19 d, and infection with M. gallisepticum or M. synoviae was found neither serologically nor clinically during the trial. The results demonstrated that intermittent pulse administration of TIA at 50 mg/kg + CTC at 150 mg/kg from d 1 to 10 and d 21 to 27, along with continuous feeding of SAL (60 mg/kg), would be possible without altering performance and while maintaining the health status of the broilers. However, further research is required on the presence of artificial infections with Mycoplasma pathogens to determine the efficacy of the combination of TIA +CTC.