Evaluation of a mixture of trimethoprim and sulphaquinoxaline for the treatment of poultry: safety and palatability studies

The safety of a 1:3 mixture of trimethoprim (TMP) and sulphaquinoxaline (SQX) for administration in food or water was assessed in broiler chickens, chicks of an egg laying strain and breeding fowl. The only effects recorded in six-week-old broilers medicated for seven days at levels ranging from 16 to 133 mg TMP plus SQX per kg bodyweight were decreases in water or food consumption, probably caused by unpalatability at overdosage levels, and associated decreases in weight gain and packed cell volume at an achieved overdose level of 4.4 times the recommended use concentration (RUC). Breeding fowl medicated at levels of 1 X or 3 X RUC for 14 days showed slightly reduced reproductive performance reflected by lowered egg production, egg weight and hatchability. These effects were temporary and performance equal to that of unmedicated birds was re-established by 14 days after medication ceased. Week-old chicks medicated for five days at levels from 0.7 to 4.7 X RUC showed normal growth rate over 12 days. Eleven-day-old chicks could not distinguish medicated from unmedicated water.