The highest incidence of high-level antibiotic grades occurs around drying-off and is most often due to cows recently treated with dry-cow therapy. Other, less common and less obvious reasons for grading at this time have been identified, including antibiotic contamination of teats or cups via personnel administering dry-cow therapy (DCT).
To minimise the risk of grading around drying-off, the following is advised:
- Allow time and ensure people are available to administer DCT properly and cows are marked and recorded adequately
- Have people who are not milking administer DCT. There are incidences where antibiotic has been transferred onto cows' teats via the hands of people administering DCT and subsequent inhibitory substances ( IS) grades
- Better still, bring cows back in immediately after milking
- If cows are treated while others in the herd are still milking, make sure treated cows are kept securely well away from the milking herd
- Make sure everyone knows how treated cows are marked and what to do should any treated cows re-enter the herd
- Any suspicion that contamination of the vat has occurred - contact the dairy company
Inadvertent double treatment
Giving two tubes of DCT to a quarter alters the antibiotic residue profile and IS grading risk at the start of the season. Double treatment can be avoided by marking treated cows and having a pre-determined order of administration of DCT (e. g. BL-FL-FR-BR).
Volume at drying-off
The volume of milk a cow produces toward drying-off has an effect on how antibiotic behaves in the udder. DCT applied to cows once dry will produce extended periods of antibiotic residue in milk post-calving.
When a herd average is below 5L, there will be individuals that are virtually dried off and therefore likely to have prolonged residue profiles.
Penalties for IS where withholding periods are complied with and stock are well managed are rare. Ensure you avoid IS grades by following the recommendations of your prescribing veterinarian.
