In June 1995, the APVMA released an interim report, Ad hoc review into the use of chlortetracycline in pigs. The report (which is available from the APVMA) identified off-label use of chlortetracycline for extended periods of treatment as the major contributing factor in the residue violations. A change in testing methods in the second half of 1993 was also identified as a possible contributor to the sudden increase in the detection of residue violations.
The interim report proposed increasing the Australian MRL from 0.05 ppm to 0.60 ppm in pig offal (kidney) to more closely align with the MRLs of the European Union, the United States and the Codex Alimentarius Commission.
At the start of the review, the use of chlortetracycline in cattle and sheep was not supported due to a lack of data and the uses were withdrawn. Temporary MRLs were set for sheep and cattle to allow the sale of existing stocks. The temporary MRLs were to expire on 31 December 1998.
During the data evaluation, the APVMA investigated not only residues in pigs but also residue-related aspects of all use patterns of chlortetracycline in commodities. Subsequently, the APVMA released the Draft review of chlortetracycline for public comment in November 1998 (the draft is available from the APVMA).
The APVMA re-examined the use of chlortetracycline in cattle and found that the existing MRLs for cattle were now supported by adequate data. The APVMA proposed confirming them as full MRLs.
The APVMA further proposed ceasing the uses of chlortetracycline in sheep, lambs and lactating animals as there were insufficient data to support them. The use of chlortetracycline in animals producing milk for human consumption was also not supported.