Feeding waste milk has always attracted strong opinion with concerns over disease transmission, calf health and, more recently, whether it leads to mastitis in heifers at calving.

Research has shown links between calves fed mastitic milk and the incidence of mastitis when first calving, says parlour specialist Ian Ohnstad of The Dairy Group. He believes waste milk is an issue of risk management.

“Work from South America has shown calves fed infected milk had mastitis as fresh calvers caused by the same genotype of bacteria. Feeding reject milk depends on your view on risk – when you are risk averse by nature, don’t do it.

The same argument goes for antibiotic and high cell count milk,” he says.

But with DEFRA now advising producers against feeding TB reactor milk (banning it completely in Northern Ireland) as well as a growing awareness of antibiotic resistance, some producers could be pouring a lot of reject milk into the slurry pit.

The answer could lie with on-farm pasteurisation, says vet Roger Blowey of Wood Vet Group, Glos.

He sees no problem in feeding antibiotic or mastitic milk to calves.

“Our most common bugs that cause mastitis are found all over the body, so even a calf suckling teat skin is ingesting Strep uberis, coliforms and/or Staphs.”

As for antibiotic milk, he says producers have fed milk containing cloxacillin for 45 years and no one has yet isolated a resistant Staph or Strep bacterium.

“Furthermore, some 90% of cows have had dry cow therapy – colostrum, therefore, contains antibiotics.

It’s illogical to ban waste milk on this basis.

“This waste milk has good nutrient value and contains antibodies which are not found in milk replacer.

The downside is variation, as it isn’t a consistent quality.”

Pasteurising, however, could reduce the bacterial loading of waste milk and help improve quality as well as control Johne’s disease, adds Mr Blowey.

Herds infected with Johne’s shouldn’t pool colostrum or feed milk from infected cows to calves, he explains.

Any offspring from a Johne’s dam should be identified by legband and her milk thrown away if she has mastitis.

There is good evidence from the USA that pasteurising milk can remove Johne’s pathogens and mastitis-causing bacteria.

To establish the benefit of on-farm pasteurising in Britain, Mr Blowey is hoping to conduct a trial in a 340-cow herd which has a high incidence of Johne’s.

A DeLaval small suspended heater, costing about 180, will pasteurise waste milk on a low temperature and long time basis.

Commercial batch pasteurisers have been used in the USA on farms for several years, mostly for pathogen control, says New York based vet Sam Leadley.

Two main types are low temperature/long time (heating to 62.7C for 30 minutes) and high temperature/short time (71.6C for 15 seconds).

Both methods are said to kill mycoplasma and Johne’s pathogens.

“We tend to pasteurise for pathogen control – infectious diseases such as Johne’s and salmonella and run of the mill pathogens such as coliforms, Strep and Staph species.

In my experience as long as the milk going into the pasteuriser has a standard plate count of less than 1m colony forming units the pasteurised milk will be virtually bacteria free.”

Dr Leadley says producers report a drop in scours from feeding pasteurised reject milk, an increase in weight gain and improved treatment responses for respiratory illness.

fwlivestock@rbi.co.uk