Part one - Around drying off
The majority of inhibitory substance (IS) grades are attributable to risky on-farm management practices particularly relating to the periods of time around drying off and/or calving. This is when most antibiotic grades occur and are most frequently as a result of cows recently treated with dry cow therapy (DCT).
There are a number of steps that can be taken to minimise the risk of grading particularly around drying off. These include:
- Allow time, have adequate numbers of capable staff on-hand, ensure that cows are clearly identifiable and their numbers are recorded adequately.
- Only infuse DCT once all cows have been milked. Bring cows back in immediately after milking, once all cups are off.
- If cows are dried off in batches, make sure treated cows are kept separately and are 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. This may save getting a grade or lessen the penalty imposed.
Every DCT season we invariably have a number of calls asking what to do if a cow has inadvertently received double treatment. To decrease this risk mark treated cows clearly and have a pre-determined order of administration of DCT (eg. BL-BR -FR-FL). Administering two tubes of DCT to a quarter alters the antibiotic residue profile and increases the risk of an IS grade at the start of the season.
The volume of milk a cow produces toward drying off affects how antibiotic behaves in the udder. DCT applied to cows once dry will produce extended periods of antibiotic residue in milk post-calving. Individuals that are producing less than five litres per day (or <0.4kgMS/cow/day) are getting close to drying themselves off and are likely to have prolonged residue profiles.
periods are complied with and stock are well managed IS grades are avoidable
and penalties are rare. To complete the picture, check out Part two - Around calving.