Dr Vernon Fowler, from the Rowett Research Institute in Aberdeen, says adding a sugar found in pig's milk to animal feed promotes beneficial flora in the gut.

This has the effect of driving away the harmful bacteria that can cause digestive tract infections, diarrhoea and even death.

BBC Science correspondent Pallab Ghosh reports

Currently, low-dose antibiotics are routinely fed to animals on intensive farms. This protects them from illness and has the added benefit of promoting growth - animals get fatter, quicker because they do not waste energy fighting disease.

But there is widespread concern that the continued use of so-called growth promoters will lead to the emergence of antibiotic-resistant strains of bacteria.

This could endanger human health if the bacteria got into our food. In theory, disease could also spread if the animal microbes passed their drug-resistant genes to human bacterial strains

In response to these concerns, the European Union will ban the use of some growth promoters this summer. This will leave farmers looking for alternative ways of protecting the health of their herds.

Chinese piglets

Dr Fowler's approach exploits the properties of lactose, a sugar unique to mammalian milk. It is readily fermented by friendly bacteria such as lactobacilli, but is disliked by diarrhoea-causing strains of microbe.

The pigs given the new feed did as well as those given antibiotics

"What we're trying to do is to feed the friendly bacteria in the gut and displace the hostile ones and that's exactly what antibiotics do," Dr Fowler says.

"They shift the balance from unfriendly bacteria to friendly bacteria - we're trying to do that in a more natural way."

Dr Fowler hit upon the idea of introducing the sugar into feed after seeing completely disease-free piglets on a trip to rural China. These animals were fed finely chopped root vegetables and continued suckling to an advanced age.

The Aberdeen researcher has used this knowledge to produce a special, slow release food additive using the complex sugars from plant roots and the lactose from pig milk.

Dr Fowler has been giving the new feed additive to pigs on an experimental farm for the past eight years. He says the animals do just as well as those fed with antibiotics.

"The bacteria won't become resistant using this approach in the way they've become resistant to antibiotics in the past. They learn ways of beating the system when antibiotics are used."

Farming practices

Local Aberdeen farmer Kevin Gilbert has stopped using anti-biotics in anticipation of the EU ban. He believes farmers will welcome the new approach.

"We're pretty angry in Europe," he says.

Pigs on intensive farms are weaned early

"We're being hit with another piece of legislation. We're losing another management tool that the rest of the world has. We're having to compete on a world market - so yet again it's adding to our cost of production"

Dr Bill Mullen of the Rowett Institute has set up a company to commercialise the new pig feed and to develop better farming practices.

"We need to make sure that animals for humane reasons are reared in the best possible way and we need to make sure that any products that come from animals - be it milk or be it meat - are as safe as they possibly can be to eat"

The Rowett plans further tests on animals other than pigs.