Pre-harvest salmonella reduction: the next step
Achieving continuous improvement will dictate that salmonella control strategies start before the processing plant.
Over the years, the USDA has instituted more strict regulations in the processing plant with regard to the presence of pathogenic bacteria, such as salmonella, on poultry carcasses. The intention of these regulations is to ensure that the processing plant employees keep the number of salmonella positive carcasses that leave the plant, or that are cut-up and made into other products, below a national standard.
When a poultry company exceeds the salmonella standard set by the USDA, the initial reaction is to place blame on the plant employees. Various companies have spent enormous amounts of time and money attempting to reduce salmonella levels on finished carcasses by making changes in the plant. Unfortunately, this is not always successful. Numerous factors during breeding, hatching, growout, and transportation (chick and broiler) can directly impact the level of salmonella on the finished product.
The following is an example of how these factors, which have nothing to do with processing, can significantly influence carcass salmonella results. In one instance, a processing plant had a salmonella prevalence of 17.5 percent. Another processing plant owned by the same company had a salmonella prevalence of 6.7 percent. The company suspected that the plant that had 6.7 percent prevalence was doing an excellent job with processing, but had a problem with flocks that were "hot" with salmonella. When the source of birds for the two plants was switched, instantly, the salmonella prevalence for the first plant went from 17.5 percent to 25 percent. The salmonella prevalence for the second plant fell from 6.7 percent to 1.6 percent. This effect held up over a few months. These data clearly demonstrate that just by manipulating the flocks that go into a plant, the prevalence of salmonella within that plant may be significantly impacted. In the case of the first plant, the salmonella level was acceptable and within USDA specification at 17.5 percent. However, by processing more contaminated flocks (25 percent), the level exceeded the USDA limits.
In this example, the company failed the USDA salmonella testing series and spent an enormous amount of money and effort to clean up the plant even though it was in excellent condition. In another instance, a company had a very similar situation that led to finger pointing between processing and production. The processing management knew that the plant was clean and that all efforts were being made to reduce salmonella in the plant. The production people felt that "this is a processing problem" and did not want to get involved. In actuality, it is a "company" problem, and cooperation between processing and production is essential to identify and solve situations such as this.
Another major problem is that growout houses can become "hot" with high salmonella populations without warning and may stay "hot" for a long period of time. This may vary due to weather conditions, insect or vermin infestation, problems with salmonella cross-contamination at the hatchery, or season. Although the processing plant employees have the regulatory responsibility to ensure that the product meets or exceeds the salmonella regulation, they have absolutely no control over these production factors. Management within a company must work together to identify and solve problems.
The breeder chickens have been a cause of concern for the poultry industry for many years with regard to salmonella. Salmonella may be transferred on the surface of the egg shell due to fecal contamination during laying, or it may be encased within the egg. To prevent vertical transmission of salmonella, many companies have instituted a vaccination program, but these programs have met with mixed results.
An approach that many European countries use in breeders and meat birds is competitive exclusion. The idea is that by feeding the chickens populations of "good bacteria", these good bacteria will colonize the intestines of the chicken and inhabit salmonellas preferred attachment sites. The cultures used in these countries contain bacterial species that are not defined and identified. The U.S. Food and Drug Administration will not allow these cultures to be used in the USA. In Europe however, the undefined cultures have been demonstrated to be successful at reducing salmonella.
Research has demonstrated that contamination of raw poultry products with Salmonella spp. may be attributable to cross-contamination in the hatchery from salmonella infected eggs or surfaces to uninfected baby chicks during the hatching process. During the hatching process, Salmonella spp. is readily spread throughout the hatching cabinet due to rapid air movement by circulation fans. Researchers have demonstrated a link between cross-contamination in the hatchery and contaminated carcasses during processing. Suggestions for elimination of salmonella in the hatchery include disinfectant fogging systems, electrostatic spraying systems, torough cleaning and disinfection of setters and hatchers and inspection and micro testing of cleaned surfaces in the hatchery.
Feed withdrawal prior to catching birds for market is a necessary step to prevent fecal contamination of carcasses during processing. Unfortunately, hungry birds in the house forage for food and ingest litter which can increase salmonella colonization of the crop. Some companies have been successful at controlling salmonella in the crop by acidifying the bird's drinking water during the feed withdrawal process.
Another popular method for reducing Salmonella in broiler chickens is to spray the chicks with a live vaccine in the hatchery. The two main companies that produce these vaccines are Fort Dodge and MeganVac. Using vaccines, companies have observed salmonella reductions of 20 to 50 percent.
Reducing salmonella on fully processed, ready-to-cook carcasses requires a comprehensive approach that includes the entire integrated broiler operation. Efforts should be made during breeding, hatching, growout, and transportation to reduce salmonella prior to processing. All emphasis should not be placed on the processing plant, nor should all of the blame be placed there. Introducing the interventions described above may have a tremendous beneficial effect in terms of reducing salmonella on processed carcasses.