Controlling somatic cell count

When faced with a steadily rising bulk tank somatic cell count (SCC) it is often tempting to try and think of some “quick-fix” solutions.

However, reducing a herd’s cell count effectively and sustainably should be a gradual step-by-step process examining all the factors at play.

Identifying and treating problem cows

Using individual cow somatic cell count (ICSCC) recording data is a useful tool in reducing the overall herd cell count. Recently there have been some new developments in how your vet can analyse cell count data – including Clover Cell Check, which categorises cows and gives individual advice on treatments.

When considering whether a cow is infected with mastitis, it is generally accepted that a cut-off of 200,000 cells/ml is used. Those cows with a recording of greater than 200,000 are highly likely to be infected on at least one quarter.

These cows are then subdivided into “first” (SCC>200,000 at their first post-calving recording), “new” (recently infected cows), “repeat” (persistent offenders within a lactation) or “chronic” (infected for two months or more) cases. Suitable treatment methods can then be applied, depending on which of the above groups a cow is classed in.

For example, long-term chronically infected cows are often unlikely to respond to treatment within a lactation and dry cow therapy is more effective to cure these animals. This could involve early dry-off of all four quarters (including an injectable antibiotic when there has been prolonged sub-clinical mastitis) or drying off infected quarters (identified by the California Milk Test) only.

Short-term chronic cows and those in the “repeat” category are more likely to be cured with intra-lactational treatments.

Appropriate therapies for these animals would be either to tube the affected quarter(s) for prolonged periods (at each milking for at least one week) or to use tubes in combination with an injectable antibiotic. The latter protocol is sensible when more than one quarter is affected, and may work out cheaper than tubing multiple quarters for prolonged periods.

Preventing new cases

Batches of frozen milk samples taken from clinical cases and chronic high cell count cows can be very useful to identify bacteria causing problems. Ask your vet about sampling methods, which need to be strictly hygienic to prevent contamination.

After analysis of ICSCC data along with culture and sensitivity results to establish whether the problem is lactational and/or dry period, environmental and/or contagious in origin, the following questions can be considered:

• Would the use of internal teat sealants, reducing stocking density and improving cleanliness reduce dry period new infections?

• Are cows being dried off rapidly then housed away from sight and sound of the parlour?

• Is a dry cow therapy that is appropriate for the particular bacteria on the farm being used, and is it applied hygienically?

• Is teat preparation pre-milking adequate – is the teat dipped/sprayed then left for 20-30 seconds before thorough drying? Are the teat cups applied at least 60-90 seconds after the first touch of each udder?

• Are there any practical changes that can be made to lactating cows’ housing which may improve the situation? Cleanliness scoring the herd may give an idea as to the degree of contamination of the udder from the environment.

• Do cows lie down too frequently immediately post-milking?

• Is post-dipping/spraying thorough enough? Would a different dip/spray be more effective?

• Would milking high cell count cows in a separate group after all other cows have been milked be beneficial?.

• Would back-flushing clusters be beneficial?

• Does a larger than expected number of cows have high teat-end scores? What is the incidence of liner slip?

There are so many different contributory factors to a high cell-count herd that tackling the problem can seem daunting. However, with appropriate vet involvement it is possible to systematically work through the problem.

With every 50,000 increase in herd SCC over 200,000 it has been shown that there is a 5% reduction in milk yield. This means there are significant financial incentives for farmers to sort the problem before any penalties or lost bonuses from the milk buyer occur.