Food safety interventions that reduce Salmonella in poultry live production

Reducing Salmonella in poultry live-production operations can be an effective means of reducing the food pathogen in the poultry processing plant and the final consumer product. Vaccination, organic acids and probiotics are among the interventions that work to reduce Salmonella levels of broilers arriving at the slaughter plant, but a carefully focused plan is required for success.

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Food safety programs are most effective when the overall pathogen load reaching the plant is not too high.
Food safety programs are most effective when the overall pathogen load reaching the plant is not too high.

Reducing Salmonella in poultry live-production operations can be an effective means of reducing the food pathogen in the poultry processing plant and the final consumer product. 

Speaking at the International Production and Processing Expo, Dr. Charles "Chuck" Hofacre, University of Georgia, outlined food safety interventions that work to reduce Salmonella in poultry live-production operations.

The secret to effective Salmonella reduction at the farm level is focusing interventions at key control points, especially at the breeder flock level, he said.

Hofacre explained why it is ineffective to attempt to control Salmonella only at the poultry processing level, and he discussed the following interventions for lowering Salmonella in live-production operations:

·         Salmonella-free breeders

·         Salmonella-free feed

·         Competitive exclusion

·         Breeder vaccination

·         Organic acids in feed or water

Why reduce Salmonella on the poultry farm?

"By reducing the level of Salmonella coming into the poultry slaughter plant, it is quite a bit more effective to reduce Salmonella there and in the final product," Hofacre said.

He presented data showing that in-plant interventions work to reduce Salmonella levels (see chart, "Why Salmonella prevalence on the farm matters"), but food safety programs are most effective when the overall pathogen load reaching the plant is not too high.

"Poultry processors do quite a good job of reducing the Salmonella levels in their plants," he said, "but there is a wide distribution of Salmonella loads coming into the plants."

In a study that collected 20 samples from 55 broiler flocks arriving at     the processing plant, there were six flocks in which no Salmonella was detected but four flocks with Salmonella detected in all 20 birds sampled. There was a wide distribution of Salmonella prevalence in the samples from the remaining 45 flocks.

"Those flocks with the highest Salmonella levels - the high outliers - are of the greatest concern for food safety," he said.

Salmonella control: Start at the breeder level!

What works to reduce Salmonella levels in poultry live-production operations? The answer is different from company to company and from complex to complex, Hofacre said, and every aspect of a poultry operation needs to be evaluated for its contribution to the level of Salmonella. Achieving meaningful overall reductions in the levels of Salmonella reaching the processing plant will require interventions at multiple steps of the live-production operation, he said.

The phase of live-production that should receive primary focus in Salmonella control, however, is the breeder operation, according to Hofacre.

"If I owned this broiler company, called the U.S. broiler industry, which has 70 million breeders, and which produces 8.5 billion broilers annually, I would first put my money on reducing Salmonella levels in the 70 million breeders, rather than in the 8.5 billion broilers," he said.

Evidence of Salmonella's vertical transmission

There's evidence to show that vertical transmission is a significant factor in Salmonella's prevalence. Hofacre and other researchers conducted a study in which 7,408 samples were collected from 49 breeder and broiler farms. About 22 percent of the samples (1,642 isolates) were positive for Salmonella. The most prevalent strain among the isolations was Salmonella Kentucky. DNA testing of the isolates showed the identical fingerprint of Salmonella Kentucky at all levels of the broiler integration - from primary breeder to parent pullets to hens to broiler houses to ceca in the slaughter plant.

"I believe 80 percent of the Salmonella on broiler farms is from vertical transmission, or from the hens to the chicks," he continued. "Now, I don't mean that the Salmonella load on the broiler farms all came from the breeders. What I am saying is that if there's Salmonella Montevideo on a broiler farm it probably originated from the breeders. If a breeder flock is shedding a high level of Salmonella then that high level ends up on the broiler farm.

"My 30 years of experience tells me that about 80 percent of Salmonella at the broiler farms comes from upstream in the production chain. You can think of it like a faucet dripping into a bucket. The bucket ends up being full after a period of time. The Salmonella being transmitted from the breeder flocks to the broiler farms is like that. Our job is to try to turn that Salmonella off at the tap."

The control challenge: Ubiquitous sources of Salmonella

Turning the Salmonella faucet off is not a simple task, however, and requires the establishment of interventions for many different vectors. In addition to hen-to-chick transmission, potential vectors include the following:

·         Insects, such as flies, beetles (Alphatobius diaperinus)

·         Rodents, including roof rats, Norway rats and house mice

·         Feeds and their ingredients, including poultry byproducts, meat and bone meal

·         Litter and dust in the poultry growing houses

·         Drinking water, which can be a means of spreading Salmonella bird to bird

Hofacre explained the nature of the challenge posed by the vectors: "Salmonella normally inhabits the chicken's intestine, so we are talking about eliminating something that is normal to the chicken. It is the almost perfect host:parasite relationship. The host does not hurt the parasite; and the parasite does not hurt the host. The Salmonella organism has a rather simple purpose in life as follows: Get into the intestinal tract of a host animal; multiply; get out of the host animal alive; find another intestinal tract as soon as possible."

Focused plan needed for Salmonella reduction

Hofacre said production managers need to look at each of the potential sources of Salmonella into their broiler and breeder houses in order to come up with a focused plan of control.

"Generally, the Salmonella interventions that are needed are different from one company or poultry complex to the next. The controls [listed below] are ones that tend to be the [most] effective from company to company in helping reduce Salmonella at the farm level," Hofacre said.

Pest management: Timing, details important

Insects, such as flies, need to be controlled through baiting and other measures because they are vectors of disease organisms. The common house fly (Musca domestica) develops from egg to adult in just seven days and travels one to three miles to feed. Control of moisture, which the fly larvae need, is important.

Beetles (Alphatobius diaperinus) are a potential vector for Salmonella Typhimurium, which can live in beetles at least 60 days. Beetle populations should be controlled.

Rodents are best controlled with baiting during periods when flocks are not present in poultry houses. Location of rodent baiting is determined by species. Mice are a bigger issue than the rats for Salmonella control.

Feed management: Breeder feeds need special consideration

Feed is a potential Salmonella vector that gets a lot of blame, and must be considered in control programs, but Hofacre is not convinced it is a major source of Salmonella in poultry. Nonetheless, ingredient purchasing, especially for breeders, can be a factor in controlling Salmonella. Strategies to consider include feed decontamination through heat treatment.

"I am not convinced that feed is a major source of Salmonella in broilers. Also, I am not convinced that feed is a major source of Salmonella in breeders. However, the use of feed ingredients with a high level of Salmonella - for example, poultry byproducts and meat and bone meal - can lead to the presence of Salmonella in the finished feed. Since breeder feed is not pelleted, and as such is not heat conditioned, Salmonella can be an issue in breeder flocks."

Hofacre said the use of organic acid/formaldehyde can be an effective Salmonella control, especially in breeder feeds. He cited a study by Maltho in which the use of propionic acid (0.2 percent) along with heat treatment (71.1 C for 80 seconds) resulted in 2 log10    lower Salmonella than heat treatment alone.

Cleaning and disinfection: Raising the bar?

Hofacre said the proper cleaning of growing houses between flocks can play an important role in reducing Salmonella in live poultry. He also said U.S. poultry producers should evaluate the possible benefits of disinfecting growing facilities.

"No, we don't disinfect broiler houses in the United States," he said, "though outside the U.S. it done. But we may need to begin considering the possibility of doing so, especially in breeder pullets."

His recommendations for cleaning and disinfection included the following:

·         Bait for rodents, first

·         Blow down dust

·         Remove all litter/manure and properly dispose of away from the farms

·         Use hot water to wash facilities/equipment

·         Use detergents to wash facilities/equipment

·         Use disinfectants

·         Apply insecticides, last

Drinking water: It's a numbers game

While drinking water may not be a source of Salmonella in poultry flocks, it can be a means of the spread of the organism from bird to bird.

Why pay attention to this seemingly less important factor?

"Salmonella control is a numbers game, he explained. "It is not a matter of suddenly eliminating Salmonella in poultry flocks. There will be a bird or two or even a hundred in a flock that are Salmonella positive. And we want to keep it at a bird or two or a hundred that are Salmonella positive. We don't want the numbers of positive birds to grow to a thousand or 10,000 in a 30,000-bird flock. And drinking water is one way that Salmonella can easily spread from bird to bird."

Hofacre cited a study by Jones in which flocks given chlorinated water at least once per week had significantly less Salmonella.

Contaminated litter: Managing with the right tools

Managing the moisture and pH levels in poultry litter is essential to reducing and controlling Salmonella in live-production operations.

Hofacre cited another study by Jones which showed water activity affects survival of Salmonella in poultry litter, with 20 percent to 25 percent less Salmonella when it is managed correctly. Treatment with propionic acid (50 percent), aluminum sulfate and sodium bisulfate was effective. All of these agents work by lowering litter pH (from 8.0 to 9.0 down to 4.0).

Managing gut flora to prevent Salmonella colonization

Managing gut flora can be an effective means of preventing Salmonella colonization in broilers. The establishment of normal avian gut flora (NAGF), for example, in day-old chicks has been shown to prevent birds from being colonized with Salmonella.

"Production managers have to find those interventions that work well in their company's live-production system," Hofacre said. "Some interventions that might work well in a neighboring complex might not work so well for your complex."

Feeding probiotics

Hofacre cited a study in which a Bacillus licheniformis probiotic was fed to birds. "The survey results show that the treatment with Bacillus licheniformis significantly reduced the presence of Salmonella in broilers when they were challenged with Salmonella Heidelberg."

He prefers to use Bacillus products in the feed over those used in the water. "A grower may fail to place the treatment in the water. However, addition of the treatment in the feed is a sure way to get it administered."

Other ways in which the normal intestinal flora can be altered include the use of botanicals and natural oil products. "Some of those work very well to help develop the normal flora within the intestine," he said.

Organic acids in drinking water

The administration of organic acids in the drinking water has been shown to significantly reduced the amount of Salmonella in the broilers. In a study, Organic acid in the drinking water reduced Salmonella incidence and shedding. There were two different inclusion rates for the treatment. At the higher inclusion rate, the birds reduced their water consumption.

Vaccination is a key Salmonella control strategy

Experts at the FAO/WHO technical meeting on Salmonella and Campylobacter in chicken meat, in Rome, Italy, in 2009, agreed that vaccination is a key means of controlling Salmonella in broilers.

Following are Dr. Hofacre's opinions about the use of live vaccines to control Salmonella:

 

·         The use of live vaccines will not make Salmonella-positive chicks negative

·         Salmonella Typhimurium vaccines do not give protection for Salmonella Enteritidis.

·         Live vaccines do not provide immunity to all Salmonella serotypes

·         Live vaccines will reduce fecal shed

·         Live vaccines provide early protection almost like competitive exclusion

·         Live vaccines don't prime the bird's immune system for the killed vaccines

Killed vaccines

Dr. Hofacre shared the following points about the use of kicked vaccines to protect against Salmonella:

·         Birds respond poorly to bacterial vaccines

·         Two injections are needed before the start of lay

·         They provide protection only to serotypes in the vaccine

·         Killed Salmonella Enteritidis vaccine won't protect against Salmonella Heidelberg

How pullet vaccination changes Salmonella prevalence in broilers

What is the correlation between vaccination of pullet flocks and Salmonella prevalence in broiler chicken meat birds? Hofacre cited a 2010 study involving two poultry integrators. One integrator was vaccinating for Salmonella - giving two live vaccines and two killed vaccines - and the other was not vaccinating. Results of the study are presented in the Table, "Correlation between pullet vaccination and Salmonella prevalence in broilers."

Among the broilers that were the progeny of the vaccinated pullets, there was significantly less Salmonella when they arrived at the processing plant.

While the Salmonella levels in the environments of the vaccinated hens did not change materially, the hens became antibody positive and maternal antibody positive.

What's more, the chick papers in the bottoms of the hatcher trays for day-old chicks had half as much Salmonella. Also, the environments in those broiler houses had half as much Salmonella.

In a similar vaccination study, following 58 broiler flocks - and these were the first flocks into the plant - ceca were pulled at rehang. The level of Salmonella in those broilers from the vaccinated breeders - all within the same company - was about half as much as from the broilers from the unvaccinated breeders. It was also found that the 14 percent that were positive were about 50 percent lower in Salmonella level. They had about 50 percent less Salmonella in the ceca than the broilers from non-vaccinated hens.

Intestinal health impact on Salmonella levels

In a study to determine how intestinal disease effects gut flora and Salmonella levels, it was found that controlling coccidia resulted in less Salmonella. Controlling necrotic enteritis, on the other hand, had no effect on Salmonella levels. See Table, "Intestinal disease effect on gut flora and Salmonella."

"The WATT webinar in December 2013 presented data from a study where we looked at vaccinating broilers with Cocci-Vac compared to broilers that received Salinomycin for control of coccidiosis on built-up litter.

"What we saw was that administering a coccidial vaccine and looking at the oocyst shedding pattern versus the vaccine and Salinomycin. It seemed that we had the damage. The tenella caused the damage; it went away; and we had less Salmonella colonization. So, how we control cocci can significantly impact the Salmonella level."

Limitations of on-farm interventions for Salmonella

Hofacre stated the following limitations for on-farm Salmonella interventions:

·         "When it comes to on-farm interventions for Salmonella, in my experience nothing works all the time."

·         "Nothing works if the Salmonella level is too high."

·         "Nothing works as well once the flock is colonized."

·         "An intervention might work today but not tomorrow. Or an intervention might work well in one complex but not another."

 

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