Selective dry cow therapy

Date published: 1 August 2017

The purpose of antibiotic dry cow therapy (ADCT), is to eliminate existing udder infections and to protect against new infections. This strategy has been successful, with a general reduction of bulk tank somatic cell counts (SCC’s) across the country over the past decades.

So why should dairy farmers now consider a different approach?

Some reasons are:

1. Availability of teat sealants - these products have been thoroughly researched and have been found to be just as effective in preventing new udder infections as dry cow antibiotic tubes.
2. In parlour spread of infectious organisms is now generally well controlled, with a significantly higher proportion of cows ending lactation with low SCC’s, (not infected) and hence do not need antibiotics to cure a non-existent infection.
3. Research in the UK has shown that cows with low SCC’s at drying off, but treated with antibiotic dry cow tubes, are more vulnerable to e-coli type mastitis in the next lactation.
4. There is concern worldwide about antibiotic resistance and the possible transfer of antibiotic resistance from animals to people.

What is selective dry cow therapy?

The objective of selective dry cow therapy is: ‘to use as much antibiotic as necessary, (to cure existing udder infections), but as little as possible’. Cows are selected to receive ADCT using pre-defined criteria. All cows receive an internal teat sealant, irrespective of whether ADCT is administered or not.

Selection criteria

The selection criteria must be herd specific and should be developed in conjunction with the farm veterinary practitioner. What Information is required to enable the ‘selection’ process to take place?

1. Individual cow SCC data, ideally from at least three milk recordings over the previous three months.
2. Individual cow clinical mastitis history in current lactation.
3. Bulk tank SCC trends, (to guide where the bar should be set).
4. Ideally some bacteriology on clinical/sub-clinical mastitis cases.

Why implement selective dry cow therapy?

This is the general direction of travel, irrespective of opinions. There is a current trend for supermarkets/milk buyers to demand that selective dry cow therapy be practised on dairy farms, as a condition of a supply contract. Quality assurance schemes such as ‘Red Tractor’ are moving in this direction. There is potential to save money through reduced antibiotic use and less discarded milk, plus the likelihood of less e-coli type mastitis in the next lactation.

Does it work?

Research by Nottingham University has shown that dry cow antibiotics are not necessary in low SCC cows at drying off, (provided teat sealer is used). Anecdotal information from some local farmers who are practicing ‘selective dry cow therapy’ shows that it works (for them). Greenmount College, CAFRE, has implemented a ‘selective dry cow therapy’ strategy over the past winter. Results to date are very positive, again indicating that dry cow antibiotics are not necessary to prevent new udder infections in cows with low SCC’s at drying off.

Remember that management of dry cows is important, irrespective of what dry cow therapy is applied, as the dry period is a high risk time for acquiring new udder infections.

Summary

Selective dry cow therapy is a strategy to reduce antibiotic use at farm level. Information on Individual cow SCC’s and clinical mastitis cases are a must. Hygiene at drying off is paramount to success, (irrespective of what dry cow therapy is being implemented). Involvement of the farm vet at all stages of the decision making process is very important. Selective dry cow therapy is a potential win/win for the dairy farmer. Good records and a high level of management are essential. Ongoing monitoring of the outcomes of dry cow therapy is important. The selection criteria may change over time, as mastitis management is a dynamic process.