27 September 1996


High dust and ammonia levels in pig buildings increase respiratory disease risk in pigs and stock carers. But research is now targeting practical ways to cut the risk. Jonathan Riley reports

DUST in pig buildings can be reduced by 70% by coating pigs with oil at feeding time.

This is the finding of a MAFF-funded trial conducted by researcher Sara Osman at ADAS Terrington, Norfolk.

Feed, dead skin, and dried faeces plus pollen drawn in through the ventilation inlets, are the main sources of dust.

"The most dangerous form of dust is respirable dust where particles are under five microns in diameter ," says Ms Osman.

"These particles are small enough to enter the respiratory system of pig and stock carer, acting as vectors for bacteria which cause lung damage.

"Dust is, therefore, a major factor in porcine reproductive and respiratory syndrome (PRRS). And if dust levels can be reduced the disease challenge can be reduced too," she says.

When there are no animals in a building dust eventually settles. It is the pigs movement that makes it airborne again.

The trial first monitored pig movements with infra-red detectors to find out when pigs are most active, so establishing when dust control would be most effective.

Most movement occurred when pigs got up to feed and in Denmark oil sprayers are already used extensively to spray oil as an emulsion into the building for 5-10sec at feeding time.

"But, this increases humidity and adds a further respirable substance which may be a disease challenge in itself. The spray system equipment also adds a considerable cost. And, where pigs are fed ad lib, feeding times extend over a longer time period," says Ms Osman.

"So our trial concentrated on putting oil on to the pig itself – using the pigs considerable surface area as a mop for taking dust out of the atmosphere."

A wooden box 1m x 0.75m (3ft x 2ft) was placed around the feed hopper with fabric strips soaked in rapeseed oil which led to a reduction in respirable dust of 70% without causing any skin problems.

The accumulation of total dust was slower when pigs were coated in oil.

Spraying pigs with oil to reduce dust is already common practice in Denmark. But equipment is costly and humidity increases so ADAS Terrington have developed this oil box which coats pigs as they pass under oil soaked strips.