PREHAR VEST S ALM ONELL A CONTROL ... - Poultry Health Today · As part of its Integrated Food Safety Management initiative, Zoetis is helping poultry companies address these challenges

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H I G H L I G H T S O F A R O U N D T A B L E D I S C U S S I O N

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10 J U L Y 2 0 1 8 • D E N V E R , C O L O R A D O

P R E H A R V E S T S A L M O N E L L A C O N T R O L

R A I S I N G T H E S TA N D A R D F O R S A F E P O U LT R Y

POULTRY H E A L T HT O D A Y ®

Sponsored by


JON SCHAEFFER, D V M , P h D

Senior Director, US Poultry Technical Services

Zoetis

[email protected]

W E L C O M E

More stringent standards implemented by USDA’s Food Safety and Inspection Service

(FSIS) have put increased pressure on producers to reduce the prevalence of Salmonella in poultry

meat. It’s no longer realistic to expect processing plants to bear sole responsibility for food safety.

It’s therefore clear that preharvest Salmonella control has taken on added importance.

There are hundreds of Salmonella serotypes. Only a few affect poultry and, of those, even

fewer affect people. Nevertheless, FSIS considers all Salmonella types equal, regardless of serotype.

If live production and processing allow Salmonella Kentucky to slip through — a serotype that

poses little risk to consumers — it can just as easily leave the door open for Salmonella Enteritidis,

which does pose a food-safety risk.

As part of its Integrated Food Safety Management initiative, Zoetis is helping poultry companies

address these challenges. Toward that end, it organized a roundtable where poultry experts could

exchange ideas for improved control of Salmonella during live production. Zoetis is pleased to

share highlights from that discussion herein.



R A I S I N G T H E S T A N D A R D F O R S A F E P O U L T R Y

T A B L E O F C O N T E N T S

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P U B L I C H E A LT H I M P L I C AT I O N S

C O M P E T I N G S A L M O N E L L A S E R O V A R S

R E G U L AT I O N V E R S U S ‘ T R U E ’ F O O D S A F E T Y

L O O K T O B R E E D E R S

E L I M I N AT I N G W E A K L I N K S I N P R O D U C T I O N

V A C C I N AT I O N D E C I S I O N S

B R O I L E R V A C C I N AT I O N T R I A L S

A S S E S S I N G V A C C I N E E F F I C A C Y

S A L M O N E L L A A N D G U T H E A LT H

I M PA C T O F L I T T E R Q U A L I T Y

W AT E R A C I D I F I C AT I O N

E V A L U AT I N G I N T E R V E N T I O N S U C C E S S

P R E P R O C E S S I N G S T R E S S A N D S A L M O N E L L A

S A L M O N E L L A P R E V A L E N C E I N N A E F L O C K S

R E G U L AT O R Y C O N C E R N S

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K A L E N C O O K S O N , D V M

Zoetis

E L I Z A B E T H D A L E , D V M

Pilgrim’s

C H A R L E S H O F A C R E , D V M , P h D

Southern Poultry Research Group Inc.

R O B E R T O ’ C O N N O R , D V M

Foster Farms

K E N P O W E L L , D V M

Aviagen

P H I L S T A Y E R , D V M

Sanderson Farms

B R U C E S T E W A R T B R O W N , D V M

Perdue Farms

S C O T T W E S T A L L , D V M

Cobb-Vantress

M O D E R A T O R :

J E A N S A N D E R , D V M

Zoetis

P A N E L I S T S

R O B E R T O ’ C O N N O R , D V M

K A L E N C O O K S O N , D V M

E L I Z A B E T H D A L E , D V M

C H A R L E S H O F A C R E , D V M , P h D

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J E A N S A N D E R , D V M

P H I L S T A Y E R , D V M

B R U C E S T E W A R T B R O W N , D V MK E N P O W E L L , D V M

S C O T T W E S T A L L , D V M



P U B L I C H E A LT H I M P L I C AT I O N S

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S A N D E R

Let’s start by addressing why preharvest intervention is important before moving on to a discussion about your experiences and recommendations regarding Salmonella prevention and control during live production. Why is it important to reduce the load of Salmonella during live production? And is there a limit on how much Salmonella a processing plant can effectively handle? D A L E

It’s important to start taking a more

aggressive and active approach to

limiting Salmonella in live production

because ultimately, at the end of the day,

we’re engaged in food production for

people — our goal is to produce a safe,

affordable, high-quality product. That

means we’re inherently engaged in

public human health.

We’re past the point on the live side

where we can simply tell consumers to

thoroughly cook their product and wash

their knives and cutting boards. For me,

that’s why I think it’s really essential we

continue to develop Salmonella control

on the live side.

S T E W A R T B R O W N

You can get between a five- and a

seven-log reduction between the front

end of the processing plant and the other

side of the chiller. That’s pretty powerful

and often is enough to knock bacteria

down so low it’s virtually non-detectable.

It’s just not enough all the time, however.

The truth is, we don’t know when those

times are.

We’re working hard to think through that,

but the part that’s still a struggle for us, as

an industry, is to keep the pathogen load

low enough so that processing-plant

interventions can work effectively all the

time. That’s the goal, and that logically

means you’ve probably got to have

live-side intervention. Most of the industry

is working toward this end.

O ’ C O N N O R

If plant interventions don’t change at all

and suddenly your Salmonella prevalence

goes up, you almost have to assume it

wasn’t caused by the plant and that it had

something to do with the Salmonella

coming into the plant.

If you don’t reduce the levels of

Salmonella coming in, you’re leaving your

plant wide open for a lot of variability.

I have seen the prevalence of Salmonella

go up at processing depending on which

farm is being processed. The plant hasn’t

changed a thing, so I have to assume it’s

coming from the live side.

S A N D E R

What are the major types of Salmonella we need to worry about? Which serotypes pose a risk to human health? H O F A C R E

The most common serotypes for the

last 30 years in human outbreaks have

been Salmonella Enteritidis, Salmonella

Typhimurium and Salmonella Heidelberg.

Salmonella Newport and Salmonella

Infantis can also be important in

some years.

Often the other serovars are more

important one year compared to other

years, simply because they’re involved in a

large outbreak. However, S. Enteritidis, S.

Typhimurium and S. Heidelberg are the

serovars that the Centers for Disease

Control and Prevention (CDC) historically

have associated with poultry and human

foodborne illness.

?

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We’re past the point on the live side where we can simply tell consumers to

thoroughly cook their product and wash their knives and cutting

boards...that’s why I think it’s really essential we continue to develop

Salmonella control on the live side. Elizabeth Dale, DVM

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S A N D E R

Dr. Hofacre has told us the serotypes of concern to human health. What are the Salmonella serotypes you’re most often finding? S T A Y E R

S. Kentucky seems to be the predominant

species of Salmonella a lot of us are

finding. Does anyone know why?

We find other bad actors out there, but

they’re a much smaller population than

S. Kentucky.

O ’ C O N N O R

We don’t include S. Kentucky in our

autogenous pullet vaccination. I want to

eliminate or reduce the S. Heidelbergs

and S. Typhimuriums. As an industry,

are we allowing Kentucky to become

predominant because we’re trying to

prevent the top three or top four?

S T A Y E R

We’ve been using an autogenous vaccine

for over a decade in our pullets —

sometimes with, but mostly without,

S. Kentucky. S. Kentucky’s always been our

predominant species. We haven’t really

seen a change with the vaccines we’ve

been using.

O ’ C O N N O R

We’ve been using an autogenous vaccine

since 2006, and I don’t think we’ve ever

included S. Kentucky. I want to eliminate

the other serotypes.


We don’t focus on S. Kentucky in parents,

either, but for maybe a little different

reason. I just don’t believe vaccination is

going to do much for S. Kentucky.

H O F A C R E

S. Kentucky has a unique ability to

out-compete its neighboring Salmonellas.

It does that in the test tube and it does

it in the chicken. When we vaccinated

broilers with an S. Kentucky isolate as if it

was a vaccine and vaccinated another

group with one of the commercial

S. Typhimurium vaccines and then

challenged them all with S. Heidelberg,

there was a significant reduction in

Salmonella colonization when S. Kentucky

was used as a vaccine — although it

wasn’t as large a reduction of the

S. Heidelberg as the commercial

live vaccine.

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S. Kentucky has a unique ability to out-compete its neighboring Salmonellas.

Charles Hofacre, DVM, PhD“ ”

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S A N D E R

What happens if you have a high prevalence of S. Kentucky since it’s not a major food-safety threat? D A L E

For us, there’s a place for two approaches

— decreasing the prevalence and

displacing serovars of concern. It’s the

difference between food-safety regulation

and true food safety.

You’re worried about prevalence if you

know you have a serovar known to be of

concern to the CDC — and it may be in a

tray pack where you’ve got raw product

going into consumers’ homes. Then your

goal is probably going to be getting rid

of those serovars versus worrying about

failing overall counts for S. Kentucky.

O ’ C O N N O R

I completely agree. There’s a public health

risk and then there’s a regulatory risk.

Are you going to be shut down due to a

regulatory violation or are you going to be

the cause of a human outbreak? If you

have one of the top three or four

serotypes that pose a greater risk to

people and there’s a risk of an outbreak,

that’s the bigger priority and a bigger risk

for your company.

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There’s a public health risk and then there’s a regulatory risk.

Robert O’Connor, DVM“ ”

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S A N D E R

What are some of the most common ways broilers become infected with the types of Salmonella that pose a risk to human health? Does it start with breeders? O ’ C O N N O R

It absolutely starts with the breeders. We

have a lot of data on broilers, breeders

and pullets. I can absolutely see the origin

of a serotype in our pullet population that

eventually works its way to broilers. In

every case of Salmonella I’ve had to deal

with, it always started in pullets, then

went to the breeders, then the broilers.


For us, the breeder side is super-

important. We’re focused on the

Salmonella B and D serogroups. We

have three metrics in breeders: houses

that become positive for Bs, those that

might be Ds and those that are anything

else. The Bs and Ds go on a priority list

and are tracked heavily. It takes them

3 years to come off the list if they get on

it. They have to be negative for two

consecutive flocks before they get off

the list.

S A N D E R

How do breeders initially become infected with Salmonella?

H O F A C R E

You may source from a pullet farm that

has a mouse or darkling beetle infestation.

I’ve walked around pullet farms that have

the supplemental starter feeder full of

darkling beetles. Those chicks are going to

eat the beetles. I’ve worked with farms

where we’ve had to completely tear the

sidewalls out and the insulation to get rid

of the beetles. If you don’t, the next pullet

flock will be positive for that farm’s resi-

dent Salmonella. Even if you’ve gotten a

clean primary-breeder source, the pullet

farm can be the source.

It’s also important to know what

Salmonella serovars are from the primary

breeder. In one study, we followed

S. Kentucky back all the way from the

pedigrees through to the processing

plant. Even though S. Kentucky is seldom

transmitted vertically in the egg, it’s still

passing through, probably by fecal

contamination on the eggshell, from one

generation to the next.

? ?



We have three metrics in breeders: houses that become positive for

[Salmonella] Bs, those that might be Ds and those that are anything else.

The Bs and Ds go on a priority list and are tracked heavily.

Bruce Stewart-Brown, DVM

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S A N D E R

What can be done to shore up weak links in the production system that enable Salmonella to get into a flock? P O W E L L

There’s a long list of ways that Salmonella

can get into a flock. On a daily basis, there

are three things I focus on regularly. One is

the feed contamination rate. Mainly look

for coliform levels, because that’s the

easiest to find and quantitate. The other

two are the management of gut health

and rodent control.

There are certainly other potential sources

of influx into a flock such as beetles,

dust or maybe the farm is located near

a cornfield at harvest time or hay is being

baled nearby, which stirs up dust or

rodents. Additionally, Salmonella can be

amplified the last few hours birds are in

the house during feed withdrawal.


Focusing on some specific serogroups

(Bs and Ds) and those farms that repeat

on those higher-priority serogroups has

helped us narrow our focus on the “weak

links.” Study the repeating farms, look at

them from every angle — rodent control,

biosecurity, vaccination, etc. Don’t stop

till you break the cycle.

D A L E

A slow vertical leak, whether it’s in the

embryo or on the shell, is probably the

most dangerous. Then it gets into broilers,

and you have a higher number of birds

shedding it and the potential for

horizontal transmission.

But other things — biosecurity or the

people involved — are really key

regarding other points of introduction.

After the avian influenza breaks in 2015,

biosecurity throughout the entire industry

improved dramatically, especially with

respect to personnel and equipment.

However, I think there’s a blind spot — or

an opportunity — regarding structural

and pest-management biosecurity. We

have much stricter programs in place, but

there’s a perception among a lot of people

that if you have out bait boxes every 100

feet and you’re checking them, you have

a rodent-control program. That’s just a

monitoring program.

At some farms, and despite a producer’s

program and inspections, the job’s just

not getting done controlling some of the

vectors for Salmonella.

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I think there’s a blind spot — or an opportunity — regarding structural and

pest-management biosecurity. Elizabeth Dale, DVM“ ”

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S A N D E R

Most breeder flocks are vaccinated against Salmonella but that’s not the case with broilers. When should a producer consider vaccinating broilers against Salmonella with a live vaccine? An inactivated vaccine wouldn’t be used in broilers because it would have to be injected, which would adulterate the meat. H O F A C R E

I would use a live vaccine if I had

S. Enteritidis or S. Typhimurium or

S. Heidelberg in my broilers, and I needed

to get it knocked down on the broiler

farm so you have less of these serotypes

coming to the plant. The current live

vaccines are not effective against all

serovars. In other words, if I want to

lessen the amount of Salmonella

coming into the plant, then I’d consider

vaccination of broilers.

O ’ C O N N O R

Dr. Hofacre’s research has shown that a

commercial vaccine does a better job

than S. Kentucky out-competing

S. Heidelberg. That really does justify our

use of a commercial vaccine in broilers.

A lot of it comes down to cost. My pullet

population is like a tiny town. It’s not

as costly for me to use a vaccine for

that small population. But when I

exponentially multiply it into broilers, I’m

talking big money. So, I get a lot of

questions because it’s expensive to do,

but we do it and I feel we have the

science to actually show it’s a preharvest

intervention that works. W E S T A L L There are two scenarios where I would

consider vaccinating broilers against

Salmonella. One is when the plant is

having a high prevalence issue or when

you’re getting isolates of concern in

the plant that you don’t have in your

autogenous vaccine for breeders. You

might want to use a live vaccine during

that time in broilers until you get that

isolate incorporated into your autogenous

vaccine for breeders.


If you decide there’s nothing more you

can do at the plant to lower the

prevalence of Salmonella, you have to

weigh the cost of that against the cost of

a live vaccine, which can be expensive.

It’s been a number of years, but use of a

live vaccine didn’t work well in our hands,

at least with the strains we used.

O ’ C O N N O R

When we talk about live-side

interventions, there’s no silver bullet.

It’s a “multi-hurdle” approach. If I treat

the litter, use probiotics and then

organic acids before processing and

I add a vaccine to that, I’m adding one

more hurdle. Whether or not a single

intervention, among several, is effective

is very difficult to determine. Using

prevalence as the determinant is a

very gray area.

How do we know if there are synergies

among the interventions? It’s hard to

validate the worth and what you’re

spending. If I’m in the plant, I can easily

validate. So — to your point about

spending money and making a good,

judicious decision — it’s often easier to

justify spending based on experience

at the plant instead of on the live side.

continued

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There are two scenarios where I would consider vaccinating broilers against Salmonella.

Scott Westall, DVM“ ”

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D A L E

In my experience, vaccines don’t have

an impact on prevalence. They’re more

successful at displacing specific serovars.

Now, if you’re trying to get out of Category

3, you probably need a short-term and a

long-term plan. The short-term plan may

be throwing everything in the kitchen

sink at the problem, but the long-term

plan includes a lot more, as we’ve

discussed: looking at your management

practices, your litter quality and moisture,

biosecurity, your pest control, as well as

the serovars you have, and testing and

vaccination of breeders.

C O O K S O N

It’s important to hold vaccination crews

accountable to help ensure flocks are

vaccinated properly. That’s one of the

most powerful tools we have. When they

know they’re being checked, they realize

they need to bring their A game.


It’s important to hold vaccination crews accountable to help

ensure flocks are vaccinated properly. That’s one of the most

powerful tools we have. Kalen Cookson, DVM“ ”




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S A N D E R

Dr. Cookson, you’ve been involved with broiler vaccination trials. What do they show? Can they help a producer get out of Category 3? C O O K S O N

In most cases, levels of Salmonella in

the plant are driven by S. Kentucky. Not

always, but if someone is in USDA’s

Category 2, going into Category 3, or the

plant is solidly in Category 3, it’s often

80% S. Kentucky-driven. There are studies

that clearly show a reduction in

S. Kentucky when broilers receive live

S. Typhimurium vaccines. In the

field, it’s a different situation than a

controlled-challenge study, but we’ve

seen reductions in positive bird rinsates.

I just don’t think the reductions are on

the same level as we see against the B

and the D serotypes, and I think there’s a

lot of science and reason for that. There

are shared antigens between the Bs

and Ds.

S A N D E R

When did these studies begin? C O O K S O N

The broiler-pen studies started about

15 years ago. Instead of challenging the

broilers, investigators relied on what we’re

talking about here — the link from

breeder to broiler. Investigators confirmed

that chick-box papers were positive for

Salmonella serotypes B and C. There was

a 30% to 60% reduction in Salmonella-

positive carcass rinsates after rehang.

S A N D E R

Haven’t there been more recent broiler trials with the live vaccine? C O O K S O N

Yes. Since then, there have been some

fairly large-scale studies that produced

similar results. In one live S. Typhimurium

vaccine trial, there was a 60% reduction in

positive rinsates at rehang. Investigators

broke it down by serotype; Salmonella C

serotypes made up about 75% of all the

isolates recovered from the unvaccinated

birds, and Bs accounted for the other 25%.

In contrast, there was a 50% reduction

of Salmonella C and no recoveries of

Salmonella B in the vaccinates.

In a second trial, investigators saw about

a 30% reduction and that included a 25%

reduction in Salmonella C serotypes and a

50% reduction in Salmonella B serotypes.

So again, limited data confirms there

were better reductions in Salmonella B

serotypes when broilers are vaccinated.

Investigators did not see much Group D.

S A N D E R

What do you recommend based on these studies regarding vaccination of broilers? C O O K S O N

There aren’t enough numbers to make

firm conclusions. But we might infer that

if you’re in USDA’s Category 3 and that’s

driven by the presence of Salmonella

serotype C, then maybe you are willing

to spend more and vaccinate your

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broilers. You know, the earlier you can

intervene with a vaccine — like at the

hatchery — the better the chances are

for affecting change. P O W E L L

Do you find that vaccination works better

in a small-bird or big-bird program — or

any particular program?

C O O K S O N

There isn’t enough experience yet with

birds of different sizes, but investigators

did see reductions in medium- to large-

sized birds. In pen studies, they’ve also

seen reductions in birds anywhere from

7 to 8 weeks of age.

H O F A C R E

Research shows the live S. Typhimurium

vaccines do not give as much

cross protection against Salmonella C

serotypes as they do for the B and D

serotypes. If you’re in USDA’s Category 3

or are about to go there, using a live

Salmonella vaccine for a serogroup C may

not be as effective as for B or D serotypes.

Dr. Cookson, were one or two doses used

in the broiler trials you described?

C O O K S O N

Two doses. P O W E L L

Does anyone worry that use of a live

Salmonella vaccine will show up upon

testing at the processing plant?

O ’ C O N N O R

Brilliant question. We have seen it —

very, very rarely but we have seen it. But

I don’t see it enough for me to be alarmed

about it.



In most cases, levels of Salmonella in the plant are driven by S. Kentucky.

Not always, but if someone is in USDA’s Category 2, going into Category 3,

or the plant is solidly in Category 3, it’s often 80% S. Kentucky-driven.

Kalen Cookson, DVM

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S A N D E R

Let’s turn to assessing vaccine efficacy. How do each of you determine if a vaccine program is effective or not? P O W E L L

I have a burning question about

monitoring a vaccination program.

How do you measure the efficacy of

killed Salmonella vaccines, especially

the autogenous bacterins for breeders?

There are obviously ELISA tests, but

none are specific.


We get three boot-sock samples in the

course of a breeder’s life. We’ve been

doing this for about 10 years. One of the

sample sets is for pullets and two are for

hens. We get a yes/no associated with

those boot socks for Salmonella serotypes

B and D, and there’s another general

category for anything else. You put the

results on a graph and look at it monthly.

Over time, you tweak your vaccine and

watch that number. We’ve had some

cases where it moved, based on what

we believed was associated with a bad

decision in the vaccination approach.

And vice-versa. With this approach, we’ve

had a lot of success getting the

Salmonella prevalence down. But, of

course, we also worked on rodent control

and other Salmonella-control measures. P O W E L L

So you’re not measuring titers and the

vaccine efficacy itself?

H O F A C R E

No one has shown that there is a

correlation between an ELISA titer and

protection. Dr. Stewart-Brown is watching

the prevalence of Salmonella in breeders,

which will eventually show up in the

processing plant. That’s a very effective

way to monitor.

P O W E L L

What should the proportions be if

there are multiple serotypes in an

autogenous vaccine?

H O F A C R E

There’s no science.

P O W E L L

Exactly! I think such studies have merit! H O F A C R E

If you have a problem serotype you’re

most concerned about, then I would

make an autogenous vaccine for that

problem serotype. If you have two or

three problem serotypes, I would use a

vaccine for those. But I don’t like to put

more than three serotypes in a vaccine

because it’s diluting out the effectiveness.

I worked for more than 10 years trying

to use Salmonella killed vaccines

for S. Kentucky, and we were not as

successful as we had been with

autogenous S. Enteritidis or S.Heidelberg

vaccines, so this strategy may not work

as well for every Salmonella serotype.

But on S. Heidelberg, S. Enteritidis and

S. Typhimurium, they'll be fairly effective.

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No one has shown that there is a correlation between an ELISA titer and

protection. Dr. Stewart-Brown is watching the prevalence of Salmonella

in breeders, which will eventually show up in the processing plant.

That’s a very effective way to monitor. Charles Hofacre, DVM, PhD

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S A N D E R

Dr. Powell, can you tell us more about the relationship between coccidiosis and Salmonella? P O W E L L

Coccidiosis can change the gut

microflora in such a way that Salmonella

will colonize or amplify in the GI tract.

Specifically, beneficial microflora, such

as lactobacillus, decline in numbers, and

pathogenic opportunistic microflora, such

as clostridium, will proliferate.

By monitoring coccidiosis with oocyst

numbers (oocysts per gram), gross or

microscopic lesions, and with polymerase

chain reaction (PCR) to quantitate

clostridial levels in the lower intestinal

tract, I have found these numbers peak in

broiler flocks on built-up litter between

14 to 21 days of age. In antibiotic-free

production systems with total cleanouts,

you tend to see coccidial challenges later

— between 28 to 35 days of age.

To me, from a gut-health standpoint,

focusing on these times of prevalent

coccidial activity would have merit for

controlling Salmonella. S A N D E R

Do you see a difference in Salmonella

counts at processing in larger birds since they have more time to recover from a coccidial challenge compared to smaller birds? S T A Y E R

We have big and bigger chickens. We

don’t have small chickens, so we don’t

really see a difference in our Salmonella

counts relative to size. We do see

different results post-processing from

production units within 30 miles of each

other, which is probably related more to

processing-plant interventions than it

is to grow-out conditions.

D A L E

We have chickens of all sizes. We don’t

see a difference either based on cocci

cycling levels or bird size as much as a

noticeable geographic difference, as

Dr. Stayer mentioned. Whether there’s a

difference due to bird size or Eimeria

maxima, scores would be very difficult

to differentiate just because of all the

other variables — house management,

biosecurity, litter quality, the breeder

vaccination program, etc. P O W E L L

You’ve got to control coccidiosis

whether that’s in the pullet, breeder or

broiler house. A producer could have an

undetectable level of Salmonella and

then coccidiosis cycles and amplifies it.

You drop the ball on gut health, and

Salmonella is in every chicken. This is why

I focus much of the Salmonella-control

efforts on gut health.

With poor pullet immunity against

coccidiosis, it is possible to have breaks

upon the move to the breeder house,

and it wouldn’t be unusual to isolate

Salmonella in a breeder flock after that.

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A producer could have an undetectable level of Salmonella and then

coccidiosis cycles and amplifies it. You drop the ball on gut health and

Salmonella is in every chicken. This is why I focus much of the Salmonella-

control efforts on gut health. Ken Powell, DVM

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S A N D E R

Since litter quality is important for controlling coccidiosis and coccidiosis may be linked to Salmonella, would you say better litter management will help minimize Salmonella? S T E W A R T B R O W N

My favorite live-side intervention right

now is good paw health. It sounds bizarre.

But if you can have consistently good paw

health, you generally have pretty dry litter.

If you have pretty dry litter, you did a good

thing for food safety and for generally

containing bacterial contamination. Our

quantitative assessment of Salmonella

loads coming into the plant shows that

complexes with the best feet generally

have a lower Salmonella prevalence over

time. Concentrating on feet is a great

thing for animal health and for food safety.

S A N D E R

What you’re saying supports research from Mississippi State University that showed chicken feathers and feet are primary Salmonella vectors.

S T A Y E R

The point made about good paw quality

is valid since good paw health can reflect

litter dryness. But quite honestly, in our

experience, we have not seen a linkage

between paw quality — as a reflection

of litter quality — and Salmonella

at processing.

H O F A C R E

We’ve conducted several studies over

the years where we’ve looked at the

prevalence of Salmonella and

Campylobacter in broiler houses. If you

walk along the sidewall where it’s nice

and dry, you are less likely to isolate them.

If you walk in between the feeders and

drinker lines, where there’s more moisture,

you’re more apt to find Salmonella and

Campylobacter if they are in the house.

Research by Ed Mallinson 20-plus years

ago demonstrated that water activity in

the litter allows Salmonella to survive or

even multiply.

C O O K S O N

I agree that Salmonella prevalence can

relate to paw quality and litter dryness,

which we’ve sometimes seen in field

trials we’ve conducted. Prevalence can

sometimes trend up through the course

of a 14- to16-week study while other times

it may trend down, depending on whether

you’re coming into winter or summer.

Ventilation rates and litter quality are

much improved throughout most of the

country during summertime.

In Colorado, where the air is dry, we

conducted the same exact type of

Salmonella study 2 years in a row.

The first time we got a much higher

prevalence of Salmonella. The second

time we tried to keep all variables the

same, but as it turned out, the types of

pens were not exactly the same. The first

study with higher Salmonella prevalence

used solid plastic wall dividers between

pens while the second study divided

pens using mesh netting. I think that one

variable could have affected the difference

in Salmonella prevalence, with the

ventilation being better in pens with

netting so the litter dried more.

continued

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The point made about good paw quality is valid since good paw health can

reflect litter dryness. But quite honestly, in our experience, we have not seen

a linkage between paw quality — as a reflection of litter quality — and

Salmonella at processing. Phil Stayer, DVM

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I believe gut health can also affect the

prevalence of Salmonella by indirectly

affecting litter moisture. If birds have

coccidiosis and develop enteritis, for

instance, they’re going to put a lot more

moisture back into the litter, so it’s a

vicious cycle. O ’ C O N N O R

I totally agree. Enteritis goes along with

coccidiosis. I see an absolute trend upward

during January and February, which in

California are wet months. Then we hit a

very nice trough through summer, and

then interestingly, the prevalence starts to

go up again in August. Why does it go up

in August, when it’s very hot and dry?

Because that’s when we’re misting and

putting a lot of moisture into the air,

which drops on litter.


I totally agree. Enteritis goes along with coccidiosis.

I see an absolute trend upward during January and

February, which in California are wet months.

Robert O’Connor, DVM

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S A N D E R

What about water acidification? Can it reduce the prevalence of Salmonella? S T A Y E R

We’ve tried water acidification.

Sometimes you get promising results

and sometimes not. It really depends on

where you start — where your water

pH is to begin with. It’s not consistent.

H O F A C R E

I believe one of the biggest reasons for

inconsistent results with acidification is

the pH of the water to start with, which

can vary widely between neighboring

farms. I’ve conducted studies with water

acidifiers and they work really well, but

the pH and hardness of the water need to

be tested before determining what dose

or use rate to use.

D A L E

We’ve run a lot of trials with acidification,

waterline sanitation or probiotics, and that

silver bullet does not seem to be out there

yet. Nothing is consistently effective in

every location. Part of the issue with that

is having assays that can consistently and

accurately monitor the impact.

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We’ve tried water acidification. Sometimes you get

promising results and sometimes not.

Phil Stayer, DVM“ ”




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S A N D E R

How do you measure the efficacy of your Salmonella-control efforts, whether it’s vaccination or in-house interventions? What tools do you use? O ’ C O N N O R

On the live side, we use boot socks. But

I can’t tell you why a particular region or

complex almost always runs a lower

prevalence. What I’m really looking for are

trends. If they’re normally averaging about

40% and I see them creeping up to 60%,

70%, then I think, okay, we’ve got a

problem on the live side.

We consistently use boot socks on every

farm before it processes. We do it within

2 weeks of processing. There’s probably

some inconsistency in compliance to

the protocol for sampling, but again, I’m

looking for overall trends, not results at

a specific farm.

C O O K S O N

You mentioned 2 weeks prior to

slaughter? I'm curious. Is there an ideal

time to gauge that level of Salmonella?

O ’ C O N N O R

Yes, it’s within 2 weeks of processing.

Most of us see Salmonella as an

intermittently shed bacteria, and birds

shed the most during stressful periods.

In a broiler’s life, I’d say those last 2 weeks

are going to be some of the most

competitive, stressful periods of their lives,

so that’s when we test for Salmonella.

C O O K S O N

Do you try to avoid the last 2 or 3 days

before processing?

O ’ C O N N O R

The house is denser closer to processing,

which makes it harder to get four boot

socks through the house. Again, I’m

not reacting to the boot-sock results;

I’m looking at aggregated information

and trends, not the results from one

individual farm.

H O F A C R E

In a study Roy Berghaus and I conducted

several years ago,1 we evaluated whether

boot socks or drag swabs for Salmonella

correlated to the level coming into the

plant. We looked at 3 weeks, 2 weeks and

the week the birds were processed. Only

the week the birds were processed did

the results correlate to whole birds with

feathers on rinse, so you won’t have the

culture results in time to do much about it.

D A L E

There are a few companies working

on more rapid-turnaround diagnostics

that might enable us to implement

interventions. But currently, I think drag

swabs have value, especially if you’re

looking at overall trends.

For monitoring our overall Salmonella-

control program, I still look to the overall

Enterobacteriaceae count and the

Salmonella prevalence at rehang because

that’s as close as I can get to what we’re

bringing in from the field. There’s the

stress of catching and transport, but

ultimately it’s what’s coming in the door

of your plant.

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S A N D E R

Other than boot-sock sampling and environmental testing, are there any other diagnostics used to monitor Salmonella in flocks, whether that’s for breeders or broilers? D A L E

Boot socks are of limited value. You can

pick up Salmonella with boot socks but

it’s a lot easier to test, for example,

hatch-tray residue swabs or even chick

papers. There are other sampling

methods if it’s coming out of your

breeder-source flock.


We have been trying to work on an

“organic load” metric. These could be

super practical and simple but important

metrics — are the birds coming in clean

or not? We also have camera monitoring

in our processing plants now to judge

feather cleanliness and paw health at

the farm level. This results in a soiled-

feather score and a paw-health score.

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In a broiler’s life, I’d say those last 2 weeks are going to be some of the

most competitive, stressful periods of their lives, so that’s when we

test for Salmonella. Robert O’Connor, DVM“ ”

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1 Berghaus RD, et al. Enumeration of Salmonella and Campylobacter spp. in environmental farm samples and processing plant carcass rinses from commercial broiler chicken flocks. Appl Environ Microbiol. 2013 Jul;79(13):4106-14.



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S A N D E R

We need to address the impact of feed withdrawal. How does the timing of feed withdrawal affect the prevalence of Salmonella going into the processing plant? O ’ C O N N O R

I don’t think the 8 to 12 hours of feed

withdrawal prior to processing has

changed. But the longer birds are off the

feed, the more issues you’re probably

going to have with gut upset. You’re going

to stress them out, and they’ll shed more

Salmonella in the litter right before they’re

to be picked up.


I agree. But there are all kinds of other

variables at play. If we get feed withdrawal

down to 6 hours, there’s no certainty

that would help reduce the prevalence of

Salmonella going into the plant.

S A N D E R

Let’s elaborate on that point because transport to processing is a big stressor for poultry and may be associated with a bigger Salmonella load going into the plant. P O W E L L

We have those concerns when we move

breeders. If it’s a rainy day or a cold day,

you can do things like cover the transport

trailer. If we’re concerned about gut health

in stressed pullets that we’re moving to

a breeder house, we use a program with

an organic acid and probiotic, often

administered simultaneously in water.

We try to preempt stresses that affect

enteric health.


We’re looking at a new transport module

and transport system. We believe we’ll

see a significant benefit with new trailers

designed to give birds a higher level of

comfort during transport.

We also have installed a newer, full

live-haul trailer-module sanitation system.

Trailers as well as modules are fully

sanitized. The transport vehicles have

tops; the ceiling goes up and the transport

modules go on, then the ceiling comes

down. That helps with air flow. There

are also curtains. I’m excited by these

developments. These things are associated

with improved bird comfort, but I’ll be

interested to see if we get improved food

safety too.

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If we’re concerned about gut health in stressed pullets that we’re moving to

a breeder house, we use a program with an organic acid and probiotic, often

administered simultaneously in water. We try to preempt stresses that

affect enteric health. Ken Powell, DVM

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S A N D E R

Reports are mixed on the prevalence of Salmonella in poultry meat from antibiotic-free and conventional production systems. What’s been your experience with the Salmonella prevalence in flocks raised without antibiotics? S T E W A R T B R O W N

We started in 2002 moving to “no

antibiotics ever” (NAE) production in

every one of our 12 facilities. As we

progressed with the NAE program

and charted the percent positive for

Salmonellas, they were inversely

related.In other words, as NAE came in,

Salmonella came down. I’m not necessarily

attributing that to the NAE program

because we were doing a million other

things, which, by the way, I think you do

need to do.

All the breeder work had to be done

ahead of time, and that still goes on.

Gut health is really important for a million

different reasons. Gut health remains

really important not just for feed efficiency

and livability but for the food-safety

component. If you plotted our livability to

percent NAE, livability has gotten better

the last several years. But again, that’s

associated with working every aspect of

the program.

S A N D E R

Can others who have experience with both NAE and conventional flocks comment? D A L E

I can’t say that in our flocks I’ve found as

strong a consistent correlation between

NAE production and a reduced Salmonella

prevalence as Dr. Stewart-Brown has

seen. I do think that since the removal of

gentamicin from hatcheries, the industry

has seen a trend.

There are presentations at the conference

showing the difference in Salmonella loads

between NAE-type programs and in flocks

receiving BMD® after a necrotic enteritis

(NE) challenge. There are tangential or

ancillary facts associated with removing

antibiotics, but they may be related to

other health or disease conditions.

H O F A C R E

Salmonella lives primarily in the ceca. NE

occurs primarily in the small intestine. In

challenge studies where you create NE

and give Salmonella, you don’t see more

Salmonella with NE.

But when you look at what happens with

an NE flock, you get uniformity issues.

You have small birds and big birds, and

those small birds are more prone to

having crops and intestines torn, resulting

in more contamination on the carcass.

I think indirectly there’s a link for NE (gut

disease) to contribute to Salmonella, but

as Dr. Stewart-Brown said, once you learn

to control those variables and reduce your

gut-health issues, you don’t have as much

impact when you take out gentamicin.

There are ways to keep the bugs that

maintain gut health happy. The simplest

way is with an antibiotic. The more

continued

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There are ways to keep the bugs that maintain gut health happy. The

simplest way is with an antibiotic. The more expensive way to do it is

without an antibiotic, and you’re going to have to do a lot of other

things to accomplish that. Charles Hofacre, DVM, PhD

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expensive way to do it is without an

antibiotic, and you’re going to have to do

a lot of other things to accomplish that. O ’ C O N N O R We have organic flocks. We have NAE

flocks. We have conventional flocks. It

depends on who you ask and who’s giving

the answer and their biases. I don’t believe

NAE flocks are necessarily more prone to

being Salmonella-positive. And I definitely

don’t believe that if positive, they’re more

prone to have a serotype of human-health

concern. I think you’d really have to study

the data before you answer that question.

D A L E I’ll agree with that. I don’t think the hard

data is there to say one way or the other

from what we’ve seen.

O ’ C O N N O R I think there is an impact on Salmonella

prevalence in preharvest organic

production due to the restrictions on

disinfectants. If I run a probiotic, the inert

materials in it have to be organic. You are

limited more on the interventions you

can use.


I don’t believe NAE flocks are necessarily more prone to

being Salmonella-positive. And I definitely don’t believe

that if positive, they’re more prone to have a serotype of

human-health concern. Robert O’Connor, DVM

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S A N D E R

Let’s shift gears and address regulatory issues. As you know, FSIS plans to publish results of Salmonella testing for chicken parts as well as carcasses. Will this put added pressure on producers to intensify preharvest Salmonella-control programs and will it affect their relationship with their customers? O ’ C O N N O R

What they’re intending to do by

publishing results is motivate processors

to hit the standard.

S T A Y E R

If you’re in a category where you

don’t want to be, you’re going to do

everything. Then when you get where

you want to be, you’ll back down.

D A L E

I’ll echo that. You’re going to initiate a lot

of the interventions we’ve touched on and

you’re going to do more of it. The other

thing that hopefully will help us keep

moving forward will be development of

more precise assays for monitoring and

determining the impact of the different

interventions we use.

S A N D E R

Is it true that some vendor contracts specify that all their products must be sourced from Category 1 and 2 processing plants? S T E W A R T B R O W N

Sure. That’s in a number of purchasing

contracts for raw materials, generally,

based on the contracts I’ve seen.

O ’ C O N N O R

So far, I don’t feel there’s been much

customer scrutiny based on publication of

carcass findings. It’ll be interesting to see

how customers respond to publication of

results with parts.

S A N D E R

Given all the new interventions the industry has put into place, do you think we’re making progress regarding control of foodborne Salmonella?

D A L E

I have the most recent government

data here, which says that 98.5% of all

whole-chicken tests for Salmonella are

negative. That’s from large plants. Chicken

producers have reduced Salmonella in

whole chickens 66% over the past 5 years.

Those aren’t my numbers. That’s what the

government says we are doing, which is

very encouraging.

I don’t know if there’s a direct correlation

there to human cases of Salmonella,

and we’re not the only source for

those infections. But according to the

government’s own data, we are

making progress.

S A N D E R

Would you all get out your crystal ball and tell us where you think the industry will be in 5, 10 or even 15 years from now regarding Salmonella

prevention and control? D A L E

One of the most exciting aspects of this

industry for me as a veterinarian, and one

of the most enduring characteristics, is

that we have a very adaptable, progressive

industry. We’ll probably continue to

reduce Salmonella levels and maybe even

surpass what we previously thought was

impossible. Part of how we’ll be able to

do that is through better science — better

diagnostics and monitoring and hopefully

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with better vaccines as well. It’s yet to be

determined exactly which interventions

will turn out to be the best.

S T A Y E R I’d agree. Technologies need to be in

place, and I don’t think we’ve yet figured

out which are the best interventions apart

from basic good management practices.


I also agree with Dr. Dale, especially when

Salmonella and food-safety metrics start

to be managed like production metrics.

The industry once focused on production

management and has done a phenomenal

job. The more difficult task will be

applying that metric to Salmonella control

at the farm level, but once that’s done,

I think we’ll be amazed at what we can do.

H O F A C R E

Dr. Stewart-Brown and I can remember

the day when we didn’t have ELISA

testing, when it became routinely

available, and it changed the way we

actually established vaccination

programs once we could test, measure

and verify effectiveness.

There are a lot of companies really

pushing forward to find new ways for us

to test for Salmonella on the live side.

Once we have those tests, we’ll have the

opportunity to make more progress on

specific farms. I believe that new testing

methods will be one of the keys for

progress in the future. O ’ C O N N O R

Plus/minus is my prognosis. I’ve observed

that larger companies are being very

proactive. They’re moving ahead with

interventions. They’re trying to get things

in place, for instance, to meet the

standard. I see smaller companies that

want the parts standard eliminated, and

they are asking basic questions about

interventions. Based on my experience in

the industry, we’re sometimes better at

being reactive than proactive, but when

we get into a crisis — which might occur

if companies have trouble meeting the

parts standards — we are really good at

being reactive. I guess that’s my prognosis

for the next 5 years.

S A N D E R

Thanks to all of you for sharing an unbelievable amount of information and providing insights that will help the industry improve food safety and feed the world with an abundant and wholesome product. I’m proud to be a part of this industry.

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We’ll probably continue to reduce Salmonella levels and maybe even

surpass what we previously thought was impossible. Part of how we’ll be able

to do that is through better science — better diagnostics and monitoring and

hopefully with better vaccines as well. Elizabeth Dale, DVM

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