Stability of bacitracin methylene disalicylate and chlortetracyline in combination in a pelleted pig feed

A study was carried out to determine if the presence of bacitracin methylene disalicylate (BMD) interfered with the assay of chlortetracycline (CTC) and if the presence of CTC interfered with the assay of BMD when both are combined in a pig feed. In addition, the potential influence of steam pelleting on active concentrations of BMD and CTC was determined. Further, the stability of BMD in the presence of CTC and the stability of CTC in the presence of BMD was determined in pelleted pig feed. Finally, the homogeneity of BMD and CTC during normal mixing procedures and the extent of segregation during shipping were determined. The results of the study demonstrated that when present in pig feeds at levels anticipated for actual use, BMD and CTC can be assayed without interference, that each of these antibiotics remains within specifications for up to 13 weeks of storage and that standard feed mixing results in homogenous dispersion of the antibiotics which remain dispersed following transport.