Relationship of sulfamethazine in swine diets and resultant tissue concentrations, using Tishler and gas liquid chromatographic methods.
Sulfamethazine (110 mg/kg of feed) was fed to 4 groups of pigs for 10 days. Each group was then fed withdrawal rations containing 0, 1.1, 11.0, or 110.0 mg/kg of feed for 10 days before slaughter. A 5th group was fed a sulfamethazine-free diet only. Fat, kidney, liver, and muscle from each pig were analyzed by several laboratories, using the Tishler Bratton-Marshall (BM) and gas liquid chromatographic (GLC) methods. Mean background (BG) amounts of sulfamethazine, as measured in control tissues, were essentially negligible using GLC; however, BM BG values (mean +/- SD), expressed as milligrams of sulfamethazine per kilogram of edible animal tissue (ppm) were: fat 0.019 +/- 0.003, kidney 0.048 +/- 0.012, liver 0.053 +/- 0.034, and muscle 0.018 +/- 0.017. Regression of tissue sulfamethazine on feed sulfamethazine, as measured by GLC and BM adjusted for BM-BG values, yielded essentially linear plots. Values obtained by GLC and corrected BM were highly correlated, but the variability was higher, using GLC. The linear model predicted that the dietary sulfamethazine required to produce 0.1 ppm in liver as measured by the BM, BM-BG, and GLC were 1.6, 2.8, and 3.4 ppm, respectively. The concentrations necessary to produce 0.1 ppm in muscle were 5.3, 6.2, and 5.5 ppm. The thin-layer chromatographic method of screening swine plasma was a good predictor of tissue sulfamethazine values.