7 November 1997

How to stay clean & avoid costly penalties

Top quality milk will secure premium prices – its as simple

as that. Our special focus examines how to reduce mastitis

and cell counts, and avoid antibiotic penalities. To start,

Jessica Buss hears about how best to produce clean milk

THERE is no excuse for high cell counts in milk or high levels of mastitis – both of which are costly and can be kept under control.

So said Gloucester vet Roger Blowey speaking at a Mole Valley Farmers dairy conference, The Hidden Costs , at Shepton Mallet, Somerset.

Cell counts, the white blood cells that enter the udder to fight mastitis infection, should be kept under 150,000 cells/ml, he explained.

Milk buyers charge penalties for high cell counts because they lower cheese yields and can prevent yoghurt culture developing. Let them creep up to more than 750,000 cells/ml and manufactured product is reduced by 20%.

Mastitis itself is also costly, with each mild case costing £60 in yield loss, discarded milk and treatment, explained Mr Blowey.

But cell counts could be reduced in the bulk milk. "Only a small proportion of cows will be affected, so taking milk out of the tank from those cows can be more economical than the drop in bulk milk value," he said.

"Even when running at 125,000 cells/ml individual cell count testing is needed, so if cell counts increase you know which cows are the reservoir of infection, and can act quickly."

Older high cell count cows can be culled or others dried off early depending on lactation stage. When high cell count cows can be milked without risk of contaminating to other cows, feed their milk to calves – if not consider suckling calves. Treatment with antibiotics could also be considered.

Mr Blowey advised basing culling decisions on at least two high cell count results – one high result can indicate a rapid response of white blood cells to environmental bacteria that will quickly decline.

To keep cell counts under control the reservoir of bacteria causing infection must be tackled. To do this you must know which bacteria are present (see below).

High cell counts and low clinical incidence means that contagious mastitis bugs are the reservoir of infection; low counts and high mastitis incidence occurs when environmental bacteria, such as E coli, are present. These environmental bugs are picked up from bedding, and transferred during milking.

Cows are most likely to become infected from contagious or environmental bugs during milking, when the teat end is open because the impact speed of dirt on the teat end is 40 miles an hour when air is let into the machine, he warned.

To prevent this, preparation that ensures the teat end is clean and dry before milking is vital. Milkers hands must also be kept clean and washed frequently even when gloves are worn.

To ensure the milking machine is not causing high cell counts, check teat ends for damage, he said. "The end of the teat should be smooth enough to wipe across your face."

Teat damage may not just be caused by incorrect vacuum, automatic cluster removers can also be at fault, he warned. Vacuum must stop for long enough before the cluster is removed and that action should be gentle – this rule also applies to manual cluster removal.

The cluster must also hang straight and should not slip for this increases the risk of air leakage forcing bacteria into the teat canal.

Milkstone build up or poor action from worn teat cup liners can lead to sore damaged teats, increasing infection risk, so Mr Blowey advised changing liners after 2500 milkings.

He also suggested drying off abruptly – even for cows giving 30 litres; slow drying off could increase cell counts.

The end of this teat should be smooth enough to wipe across your face…

instead its sore and damaged.