Mastitis test relies on frozen glycerol
Mastitis test relies on frozen glycerol
FREEZING milk samples with glycerol before treating cows for mastitis, makes it a valuable tool for pro-active management of the disease.
Andrew Bradley, of Bristol University, explains that some bacteria are sensitive to freezing, the most seriously affected is E coli.
"After one week of freezing, 80% of E coli bacteria can be retrieved from an untreated milk sample, by three months its 30%. But when glycerol is added, more than 80% of bacteria can be retrieved after three months."
Being able to save samples is useful when treatment fails or mastitis incidence increases. Once a cow is treated and it appears to fail, how can you tell if its the original bug or a different one?
On many farms, there is a delay in identifying the cause of an increase in mastitis cases because samples are not taken until there is a problem, he says. "Unless samples are taken pro-actively and stored, you risk not gaining a true picture of what is infecting the herd."
It is hoped that glycerol-treated samples will give an accurate assessment of bacteria present when tested after a year, says Dr Bradley. Results are expected in March.
Being able to store samples from a whole lactation will help decide whether cows with repeat cases should be culled or treated. "Following three or four cases of E coil mastitis the cow can be treated with dry cow therapy and should be clean in the next lactation. But after three or more cases of staph mastitis the chances of curing her are low."
A kit for taking samples for freezing with glycerol is now being marketed by Intervet. The companys James Allcock says glycerol is safer to handle than most dairy chemicals, although he advises wearing gloves when using it.
Frozen samples can be sent to any lab offering bacteriology, as no special procedures are requ-ired. It will also be possible to take advantage of bulk discounts when testing 10 samples at once, he adds.
Intervet hopes that test kits for 10 samples will be available from wholesalers and vets at about £15 each (01908-665050, fax 01908-685606).