Feeding acids to pigs from 13-30 kg is common throughout Europe. They seem to have more effect in vegetable based diets rather than those high in animal protein. Their mode of action is complex but in part works by modification of gut bugs. This generally means the healthier the farm the lower the response. In-feed acid that has been found to work in some situations is Vevovitall (benzoic) but not cheap at around 5kg/tonne at about £1.35/kg (Aug 08). New lower inclusion products based upon medium chain fatty acids (coconut oil) are looking interesting. Few people use in-feed acids in finishing pigs now. There is mixed evidence as to whether it may help Salmonella issues due to its nature of being absorbed prior to main Salmonella populations in the hind gut. There are protected acids but these are still not used commonly. Organic acid products fall into two categories: 1) unprotected containing formic, lactic and proppionic acids in a free form and 2) protected acids, which means the acid has been modified so it is not absorbed prior to entering the hind gut. Many now believe acid in water is better than acid in feed - formic/lactic based products have given the best results in water.