Have you considered selective dry-cow therapy?

With the rise of antimicrobial resistance (AMR), the armoury of medications available to farmers when it comes to drying off their cows is set to decline in the coming years.

According to Animal Health Ireland (AHI), the practice of dry-cow therapy is being questioned in many countries – by farmers, consumers and society in general.

Antibiotic dry-cow therapy undoubtedly has an important role to play in treating infections that persist at the end of the lactation and in maximising cure rates.

However, it has been traditionally used to prevent new infections occurring over the dry period. This, the AHI says, is no longer acceptable.

Quoting recent published analysis, the organisation indicated that sales of dry-cow intramammary antibiotics were sufficient to treat 100% of the national milking herd (all quarters of all cows being treated at the end of infection).

Pictured at a recent CellCheck event in Co. Cork are: Kevin Downing (red jacket); Grainne Dwyer, AHI; William Buckley, AHI; James Wycherley; Maeve O’Connor, Dairygold; Catherine McAloon, AHI; Tom Carr, farm manager; Billy Cronin, Dairygold; Brendan Smiddy, Teagasc; and Stuart Childs, Teagasc. Image source: O’Gorman Photography

This is what is referred to as ‘blanket dry-cow therapy’, which until recently was recognised as best practice in mastitis control and has made a very positive contribution to udder health in many countries.

However, the AHI says, what is considered as best practice needs to be reviewed, as well as the implications of modifying those traditional recommendations.

Selective dry-cow therapy

An increased focus has been placed on selective dry-cow therapy as a possible avenue to reduce the use of antibiotics at drying off.

Described as an alternative to blanket dry-cow therapy, this is when only selected cows (those with infected quarters) are treated with antibiotics at drying off.

Internal teat sealer is often used in the remainder of the herd as one of the measures to prevent new infections. While this is considered a more prudent use of antibiotic and would reduce antibiotic use on many farms, AHI says that this practice is not without risks.

Key risks

The CellCheck Technical Working Group recently reviewed all of the science and research on dry-cow therapy published since the early 2000s. It identified the following risks:

  • Hygiene at drying off:
    • The first risk is of introducing bacteria when we infuse any intramammary tube into a quarter;
    • When we use internal teat seal only, there is no antibiotic present as backup and so the potential consequences are even greater.
  • Missing an opportunity to cure quarters that were infected at the point of drying off.

Is selective dry-cow therapy suitable for my herd?

According to AHI, all decisions around dry-cow therapy should be made in consultation with a vet who has knowledge of the herd, its history and environment.

Selective dry-cow therapy can be used in herds where:

  • There are good clinical mastitis records, milk cultures and at least four milk recordings in the current lactation for each cow;
  • Bulk milk tank SCC (Somatic Cell Count) is consistently below 200,000 cells/ml;
  • Clinical mastitis in the herd is <2% over the last three months prior to drying off;
  • The recent infection rate in the herd is consistently <5%, as indicated on the CellCheck Farm Summary report;
  • Hygiene standards at drying off and management of dry cows are excellent.

Individual cow selection

Within these suitable herds, AHI says, antibiotic treatment may not be required for individual cows with an SCC consistently <100,000 cells/ml and no history of clinical mastitis in this lactation. These cows should also be checked with a California milk test prior to drying off.