There is intense pressure to develop better preharvest approaches to food safety in the poultry industry right now, especially when it comes to Salmonella. Detection and surveillance are crucial to reducing incidence and improving control of the pathogen throughout the poultry supply chain.
Proposed guidelines target U.S. poultry
In October 2022, the U.S. Department of Agriculture (USDA) Food Safety and Inspection Service (FSIS) proposed framework to reduce Salmonella that indirectly expands the department’s regulatory control, with a focus on “encouraging preharvest controls to reduce Salmonella contamination coming into the slaughterhouse.”
USDA FSIS further introduced additional proposed guidance on Salmonella in 2024 that had a direct impact on the commercial poultry industry. In April, the agency declared Salmonella an adulterant in raw breaded stuffed chicken products when they exceed a specific threshold (1 colony forming unit (CFU) per gram or higher) for Salmonella contamination.
This guidance was followed by its long-anticipated Salmonella framework initiating a 60-day commentary period in July. The newest proposal establishes product standards that prevent chicken and turkey products containing Salmonella at or above 10 CFU per gram/ml from entering commerce. In addition, the proposed guidance identified Enteritidis, Typhimurium and I,4,[5],12:I:- in chicken and Hadar, Typhimurium and Muenchen in turkey as serotypes of public health significance that were banned.
Poultry processing facilities are also required to develop microbial monitoring programs to prevent pathogen contamination as a result of the proposed guidance.
“Far too many consumers become sick from poultry contaminated with Salmonella, and today’s announcement marks a historic step forward to combat this threat,” said Agriculture Secretary Tom Vilsack. “This proposed framework is a systematic approach to addressing Salmonella contamination at poultry slaughter and processing, which includes enforceable standards that will result in safer food for consumers and fewer illnesses.”
The National Chicken Council (NCC) expressed concerns about the proposed rule, calling the new guidance unnecessary.
“There is no silver bullet or one-size-fits-all approach to food safety, which is why we employ a multi-stage strategy,” Gary Kushner, NCC interim president, said in a statement. “Passing a law or regulation to fight bacteria will not magically make it disappear. This proposal will raise the price of chicken and cause millions of pounds of safe-to-eat, if properly prepared, chicken to be sent to landfills rather than dinner tables – an unconscionable thought given there are 44 million Americans who are food insecure."
Preharvest vs. postharvest
Dr. Brandon CarterCourtesy Elanco Animal Health
“One of the main challenges for preharvest is the variability that we see because it’s a biological system. We don’t – and may never – completely understand all of the sources of variation and how they occur,” Dr. Brandon Carter, technical advisor, Elanco Animal Health, said.
Variability can occur in several forms when it comes to Salmonella. Some flocks from a poultry house may be infected, while others, from the same house, with the same management, may not. Seasonal changes may be in play here, although the verdict is still out on this point, Carter explained.
One of the major challenges of detecting Salmonella in poultry is that both chickens and turkeys can harbor the bacteria without becoming sick. As a result, it’s impossible to walk into a poultry house and manually monitor for signs of clinical disease.
Instead, labor is required to collect samples, as well as a laboratory to perform tests. Costs can add up, and testing can take days, holding up the entire process. Despite this, monitoring and surveillance remain important.
“If we don’t look for Salmonella, we won’t see it,” he added. “You don’t want to wait until you have a problem.”
Know which serovars you are detecting
Arjun GanesanCourtesy Ancera
Standard Salmonella isolation techniques often only identify one or two serovars, even if there are more serovars present. This means that there could be serovars present in the feed mill, breeding hens, the hatchery, the poultry house and more that producers do not know about. And if producers do not know about Salmonella serovars, there is nothing they can do to prevent it from entering the processing plant.
“It’s like going to war at night and not having night vision goggles. You’re just going to be firing where gunfire is coming at you. You need to be a lot more strategic,” explained Arjun Ganesan, CEO at Ancera.
With CRISPR-SeroSeq, producers can differentiate multiple serovars in each sample collected. This means they are not just detecting the most abundant serotypes in a sample, but also which serotypes are present. Knowing each Salmonella serovar, including those of human health concern (HHC), can help producers pinpoint the risk in their supply chain and develop new prevention methods.
Looking at dietary solutions
Ann WoomingCourtesy Arm & Hammer Animal Nutrition
Adding nutritional supplements such as probiotics and prebiotics to poultry diets can further boost a bird’s response to stress and disease challenges. Both types of supplement help colonize broiler and turkey gut microbiome with beneficial microorganisms as opposed to bacteria like Salmonella.
“These products have been shown to boost immune responses, feed the good bacteria in the gut and contribute to an overall healthier gastrointestinal tract,” said Ann Wooming, Ph.D., poultry technical services manager, Arm & Hammer Nutritional Health.
“Salmonella will have a much harder time invading and crossing through the gut lumen in the presence of a healthy well-functioning epithelial barrier.”
Feed withdrawal for Salmonella protection
Eric Shepherd, DVMCourtesy Zoetis
Feed withdrawal should last between 8-12 hours – no more, no less.
“If you have too long a feed withdrawal, which is almost 100% of the time, it ends up causing cross-contamination in the plant,” he said. “The bird intestines become too fragile. The birds also tend to eat litter, which has Salmonella in it.”
The main purpose of feed withdrawal is to reduce contamination and minimize the weight of undigested feed in the bird's gastrointestinal tract. This is at odds with the natural inclination of broilers and turkeys – eating.
“We’ve bred them to be hungry and put a lot of muscle on fast. If there’s not feed in front of them, they’ll eat what they can find in front of them and generally that is contaminated,” Shepherd continued.
Late feed outages can also have a major impact on Salmonella levels in commercial poultry.
“When birds go back on feed, they tend to gorge feed, and it messes up the entire feed withdrawal period. If you can avoid this, that is a big key to success,” Shepherd said.
Vaccination options
Bill StanleyCourtesy Boehringer-Ingelheim Animal Health
Salmonella vaccines are offered in both live and inactivated options. Both have pros and cons, according to Dr. Bill Stanley, senior key account veterinarian, Boehinger-Ingelheim Animal Health.
In the U.S., all live vaccines are Salmonella Typhimurium mutants. In other words, they contain live strains of S. Typhimurium that have been manipulated so that once they infect the bird, they do not live long.
Live vaccines typically have the greatest effectiveness in protecting the vaccinated birds. Conversely, inactivated or killed vaccines are designed to convey immunity from hen to offspring.
There are limitations to vaccines. One is called homology of protection, which means that vaccines are customized to target specific serotypes. Vaccinating against Typhimurium will not help if the real culprit is Hadar or Enteritidis.
“Vaccines are a very useful tool in protecting flocks against Salmonella, but they have to be used as part of an overall plan. You can't look to vaccines as being the only solution,” Stanley cautioned.
No one-size-fits-all solution
James MillsCourtesy Ceva Animal Health
“It’s difficult to adopt a program for controlling Salmonella in the breeders that is also capable of protecting broilers,” said James Mills, bacteriology & parasitology project lead, Scientific Support and Investigation Unit, Ceva Animal Health. But, “if you are not trying to control what is coming into the processing facility, you’re at risk later.”
Despite these challenges, Mills believes Salmonella is a problem the poultry industry can conquer, concluding that, “challenges like this have come and gone. There will be more, but the great thing is that we all face them together with determination and vison toward the end goal, a safe and healthy poultry industry and food supply.”
What’s next for Salmonella control?
To learn more about the challenges and potential solutions for better Salmonella control in the broiler and turkey industries, attend the Poultry Future Panel Discussion: What’s next for Salmonella control in broilers and turkeys?
The panel discussion takes place Wednesday, January 29th from 8-9 a.m. EST at the Georgia World Congress Center during IPPE 2025.
Registration is FREE. For more information, go to https://www.wattglobalmedia.com/events/poultry-future-events/.
