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Different approach needed to reduce somatic cell counts in herds

by
01 November 2010, at 12:00am

reports on an international symposium on dealing with SCCs

FARM vets must persuade their dairy clients to adopt a different approach to reducing somatic cell counts in their herds, Andrew Biggs, a past president of the BCVA, told an international symposium on mastitis in Brussels in September. 

Instead of concentrating their efforts on cows with the highest individual cell counts, farmers and their vets should be focusing on those animals with only moderately raised counts. 

Those individuals with counts of between 200,000 and 500,000 cells/ml for the first time in monthly tests will be ones that produce worse results in subsequent tests.

Treating cows which have tested over one million cells/ml on two or more occasions is a waste of time and effort as these must be considered to be chronic cases which are unlikely to respond to antibiotic therapy.

“It is essential to pick the right cases to pluck off the escalator: we should not be treating broken cows, but today’s cows with mediocre cell counts may well be tomorrow’s chronic cases and we ignore them at our peril,” he said.

Cell counts are a fairly blunt instrument for dealing with cases of subclinical mastitis in dairy herds but with advanced data collection and analysis techniques they can be used to good effect as part of dynamic management policy, Mr Biggs suggested.

The goal is to use these data to set herd performance targets and prepare action lists of those cows requiring treatment – normally those cows with new infections acquired in the dry period or during the current lactation, although some cows in the very early stages of chronic infections may also be suitable. 

Decisions on how many cows should receive treatment will depend on a number of factors, such as the rate of new infections within the herd and perceptions of the chances of achieving clinical cure in that particular animal. 

But farmers should recognise that there are other ways of addressing poor performance rather than relying on medical solutions. Changes in management will often address some of the underlying problems by improving hygiene standards in the housing or milking parlour: “Treatment is only part of the story,” he said.

Inappropriate treatment

Antibiotic dry cow therapy is often used inappropriately in dairy herds because of the stockman’s concern about the cost of the product rather than choosing the right product in the right cow, said Marion Tischer, a Berlin-based veterinary consultant.

She advised applying a strategy based on testing to identify the causal pathogen and only using treatment against newly-established infections. She agreed that attention to management issues is vital in the dry cow period as the rate of new infections is determined by the cow’s physical and physiological environment.

She also recommended reducing the risk of bacteria gaining access to the udder with the routine use of teat sealant, such as Orbeseal, produced by Pfizer Animal Health, which sponsored the meeting.

Farmers producing milk with high cell counts will not only face financial penalties imposed on the whole milk but can also lose money on the processed product, said Marco Nocetti, head of the laboratory for the consortium of 405 dairies making Parmigiano-Reggiano cheeses.

Their product, known outside Italy as parmesan, is a “protected designation of origin” under EU law and the consortium imposes strict controls during manufacture to maintain quality and protect the product’s reputation.

Poorer quality milk contains less casein as a percentage of total protein and consequently produces less cheese – a standard 1,100kg vat of raw milk with a 250,000 cells/ml count would yield 1.58kg more cheese than the same quantity with a cell count of 500,000.

Moreover, milk from herds with high cell counts will often contain detectable antibiotic levels which can affect the composition of the bacteria population used in the coagulation process and result in cheeses containing unsightly bubbles of gas.

Attacking the industry

Misleading information on cell counts is being used by animal rights groups as a means of attacking the dairy industry, warned Ynte Schukken from Cornell University, New York.

The campaigning group PETA has issued posters parodying the industry’s own advertising slogan “Got milk” with the provocative “Got pus”. 

But somatic cells, mainly macrophages, are a normal component of healthy milk and indeed the cow would not survive unless her milk contained these cells.

Short-term increases in the numbers of neutrophil cells are also a sign of a healthy immune system and should be of concern only if there are persistent high cell counts.

But farmers and their veterinary surgeons should maintain a focus on controlling cell counts as a quality assurance measure in an increasingly global market for milk and dairy products, Professor Schukken said.

The EU has taken the lead in pressing for improved standards and given the impact of the export trade in maintaining domestic milk prices, other exporters will have to follow. But he warned European producers that they must be seen to be playing by the rules.

If their actions are shown to be inconsistent, they may face expensive and damaging disputes with the US, conducted through the World Trade Organisation, like those that have occurred over growth hormones and genetically modified crops.