Residues of sulfadimidine/sulfanilamide and sulfamethoxypyridazine in sheep tissue.

Following treatment of sheep with different sulfonamides, residues in kidney, liver, and muscle have been determined by microbiological and chemical methods. By the microbiological method residues could be detected in kidney until the third day after the combined treatment with sulfadimidine/sulfanilamide. Using the chemical method, residues of about 3.80 p.p.m. could be found that day in kidney, while the concentrations in liver and muscle were about 1.90 and 1.20 p.p.m., respectively. On the eighth day after the last treatment traces of the medicine could be found in kidney, liver and muscle by using the chemical method. Residues of sulfamethoxypyridazine could be detected micro-biologically in kidney the second day after the last administration of the drug. The concentration at that time in kidney, liver and muscle determined by chemical analyses was about 4.66, 2.45 and 1.23 p.p.m., respectively. Traces of sulfamethoxypyridazine in kidney, liver and muscle could also be detected on the eighth day after the last medication. Considering altered metabolic rates of sick animals and variations in excretion rates between individuals of the same species, as well as variation in size of the doses applied, a 10 day withdrawal period for sulfonamides is proposed.