An obvious way to eliminate Salmonella in broilers is to vaccinate breeder flocks.
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Public interest drives public policy, so it’s no surprise the U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS) has proposed new guidance on Salmonella prevalence and monitoring at poultry processing plants.
The poultry industry is making progress — Salmonella prevalence in commercial poultry is significantly lower, based on FSIS data.1 However, the pressure is on because human salmonellosis caused by poultry has remained unchanged. The renewed effort by FSIS to reduce Salmonella contamination and illnesses associated with raw poultry products, specifically pre-harvest interventions, makes it a good time to look at your production chain and see where improvements can be made.
Vaccine is an intervention that specifically targets Salmonella from inside the bird. Therefore, FSIS is encouraging the poultry industry to use vaccine as a live-side strategy.
Origin of Salmonella
Salmonella doesn’t originate at the processing plant. It comes from live production. That’s why further reducing its prevalence will require intervention throughout the entire poultry production chain.
Unfortunately, this is easier said than done because chicks and turkey poults are easily colonized, especially during the first two weeks of life. Their normal intestinal flora isn’t fully developed, and their immune system is naïve, which makes them a receptive host for Salmonella.
In addition, our production system practices can favor higher Salmonella exposure levels every step of the way if we don’t manage them carefully. Just one example is reusing litter, which contains Salmonella, although adequate top dressing with clean, fresh shavings can reduce early exposure.
Start with breeders
There are a lot of ways young broilers and turkey poults can become colonized, and it starts with actively shedding breeders.
The most obvious way to eliminate Salmonella in breeder hens is to eliminate breeder flocks positive for the pathogen. While we all know this isn’t a realistic option, achieving significant reductions in shedding is a realistic goal if you focus on the breeder chick or poult.
One effective approach is vaccination. Researchers from the University of Georgia found that broilers had a lower Salmonella prevalence upon placement at contract farms and at processing if they were from hens vaccinated against the pathogen compared with broilers from breeders that weren’t vaccinated.2
Using a live and inactivated vaccine is complementary. I recommend giving the breeder chick or poult a couple of live Salmonella Typhimurium vaccines, such as Poulvac® ST, early — preferably on day of hatch and then a 14-day field booster — followed by an inactivated (killed) Salmonella Enteritidis vaccine, such as Poulvac SE, at 10 to 12 weeks and then one autogenous Salmonella vaccine at 18 to 21 weeks. Including serotypes from groups B, C and D should help cover the majority of poultry serotypes of concern.
Obviously, for the vaccine to be effective, it must be administered properly. Prudent operators evaluate spray and injection takes. They perform vaccination audits to ensure the vaccine handling, spray technique, spray coverage and injection methods meet expectations. And then they verify the immune response by measuring titers or antibody levels after the 10- to 12-week vaccination.
At the breeder farm, soiled and dirty eggs should be kept separate because the results with them are poor and can compromise the intervention program. If eggs are visibly clean, as they should be, and good culling practices are in place, no disinfection is needed. Egg storage is typically at 65° F to 68° F (18° C to 20° C) and should not exceed 10 to 12 days.
I am aware of some broiler producers using disinfectant wipes on dirty eggs. By compromising the protective cuticle layer, this practice can actually increase the incidence of rotten eggs forming during incubation and increase microbial contamination of adjacent hatching chicks. It masks “problem eggs” from hatchery management, gives a false sense of security to the farmer producing them and encourages the egg producer to put more poor-quality eggs into the setting egg pack.
A common practice in the turkey industry is to wash eggs to reduce microbial contamination, and most turkey breeder farms have an egg washer on site for this purpose.
FSIS has targeted a 25% reduction in infections linked to FSIS-regulated products and has recently proposed an expanded framework for Salmonella that would lower sampling thresholds and target specific serotypes of human concern at processing plants. To meet current and any future federal rules, the poultry industry will have to use all the tools in the toolbox.
Contact your Zoetis representative for information on developing Salmonella prevention and control plans for your operation.
By Eric Shepherd, DVM, MAM, DACPV, senior technical services veterinarian, Zoetis
References:
1 Peterson A. The Chicken Parts Performance Standard: Opportunities Ahead. Kemin.com. Accessed at https://www.kemin.com/na/en-us/markets/animal/poultry/pathogen-control/resources/chicken-parts-performance-standard.
2 Dorea FC, Cole DJ, Hofacre C, et al. Effect of Salmonella Vaccination of Breeder Chickens on Contamination of Broiler Chicken Carcasses in Integrated Poultry Operations. Appl Environ Microbiol. 2010;76(23):7820-7825.
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