Eau de Pig is a hit

A synthetic "pig muck" scent developed by British scientists that would put off even the most ardent suitor is attracting the attention of livestock farmers.

The foul-smelling brew was cooked up by researchers at the Institute of Grassland and Environmental Research in Devon to help identify the main constituents of the stench of pig manure.

This is allowing them to devise ways of taking the sting out of fresh country air by recommending diets for farm animals designed to cut the emissions from their waste.

Dr Phil Hobbs, one of the IGER team, said the benefits were not just aesthetic, producing a better environment for both farmer and animal, but would also make a significant contribution to reducing the levels of pollutants pumped into the atmosphere.

"There has been a lot of controversy as to what the odour was made from but we have figured out roughly what was in there and one sniff of the mix we've produced shows we're right," said Hobbs.

Up to 90 million tonnes of livestock manure is produced in the UK every year. Microbes emit a variety of gases as they break down undigested protein in the waste.

These chemicals can pollute waterways, possibly influence global warming and even damage health among those working close

to it.

Up to 40 per cent of ammonia - which can produce algal blooms in rivers - and 35 per cent of the greenhouse gas nitrous oxide produced in Europe comes from manure.

After Hobbs and his colleagues picked out the complex mixture of 15 volatile fatty acids, phenols and indoles that make up the manure gases, they found the best way to reduce the odour was to cut back on the level of crude protein in the pig's diet, which has the same impact on a pig as a hearty bean meal has on a human.

Leaving the pig feed to ferment a while, during which time many of the proteins are broken down into amino acids, is one way to improve the situation. Another method is to mix an additive into the manure itself.

Hobbs claimed the research had shown that these approaches could cut ammonia emissions by two-thirds and lower levels in 90 per cent of odour chemicals.

Meanwhile, the synthetic scent is proving to be potent stuff. In a recent experiment involving one batch sent to researchers in Manchester, three floors of a laboratory were evacuated after a spillage.