Abstract of the paper presented at the
Asociación Mexicana de Veterinarios Especialistas en Cerdos. c. c.
Guadalajara, Mexico
15 – 20th July 2003

ENTEROPATHOGENIC SALMONELLA CONTROL IN SWINE - EUROPEAN APPROACHES TO PREVENTION THROUGH BIOSECURITY AND WELFARE

Murray J Hyden, M.I.Biol, C. Biol Managing Director, Agil Ltd, UK
Ifor Phillips Technical Sales Executive, Agil Ltd, UK

A number of relatively safe drugs have been available to control disease for many years, but excessive reliance on these drugs, rather than good animal husbandry, has honed drug resistance and many of these have become ineffective on most farms. As new data is reported the European Union is restricting the use of all antibiotics and other products such as zinc oxide in pig rations. These new approaches are based on studies of the incidence of pathogenic species in raw materials, feed, housing and parent stock.

Currently, less than 5% of all animal feed produced in the UK is contaminated with salmonella and the human food poisoning serotypes - S. enteritidis and S. typhimurium are rarely isolated.

A British survey, conducted between March 1999 and February 2000, reported on the occurrence of salmonellae in pigs at slaughter. Salmonella were identified in 23% of pig carcasses.

Quality Assurance Schemes that cover all stages of production from feed through to processed meats are now commonplace in Europe. These schemes require proper monitoring of feed quality, or the purchase of feed, from a mill operating a recognised and approved quality assurance scheme. In Europe the two main schemes are the UFAS scheme, operating in the United Kingdom, and the PDV scheme, operating in the Netherlands.

The most obvious way to control Salmonella and other enteropathogens is simply to try to keep them out of the production unit. This means taking care of every aspect of production from replacement stock, feed, bedding, insect pests, rodent pests, vehicles, equipment and people.

If Salmonella or other enteropathogens are found on farm then procedures already in use have not been sufficient and biosecurity measures need to be improved. To accomplish these improvements staff training is also essential. Failure to involve staff at all levels of biosecurity will result in failure.

Disinfection routines are vital in any animal production operation and must be effective.

Feed and water must also be considered as risk areas, however, the simple addition of organic acids to the gut through the drinking water or the feed is known to be ineffective as formic acid is excreted through the kidneys almost immediately whilst acetic, propionic and other acids are generally metabolised as energy sources.

The simple addition of sufficient acid to animal feed will have little impact on pH due to the buffering capacity of the feed. However by providing an acidic environment within a bacterial supportive carrier within the intestine it is possible to promote the development of certain bacteria and inhibit others.

This method of acid delivery is so effective that these products use buffered acids to prevent restrictions to digestive enzyme activity as a result of a shift in pH. The buffering also has the secondary benefit of reducing acid volatility and corrosivity in the feedmill.

The mode of action is relatively straightforward to understand. The mineral carrier is slightly more acidic than the surrounding digesta in the gut lumen and becomes colonised by more acid tolerant, acid-producing, organisms that ferment feed carbohydrates to lactic, propionic and acetic acids.

To date many trials supporting this concept of enteropathogen control in swine herds have been reported.