Reducing salmonella risk in table egg production


Quick facts

  • Purchase chicks from hatcheries in the United States Sanitation Monitored program and pullets from sources with salmonella prevention and control programs.
  • Control rodents, insects and wild birds on your farm.
  • Clean, wash and disinfectant poultry houses between flocks.
  • Monitor bacteria on your farm through laboratory testing.
  • Attend to feed quality control and proper feed storage.
  • Properly wash and store eggs to prevent salmonella contamination.
  • Have a strong and strict biosecurity program for your farm.

Chick and pullet replacements

Chickens are very prone to salmonellosis at two ages.

  • 1 to 14 days of age
  • When pullets move to laying houses

Optimal nutrition and care can help keep your birds healthy and reduce the risk of salmonella at these ages.

  • Purchase your chicks from hatcheries taking part in the United States Sanitation Monitored program. Get your pullets from sources with good salmonella prevention and control program.
  • Have a reputable hauler for your pullets. Make sure the pullets travel in clean coops and trucks. Undisinfected coops commonly carry salmonella.


Bacterin can stop vertical transmission of salmonella in turkeys. Salmonella vaccination research is underway at the Universities of Maine and Minnesota and other places. Early signs suggest that bacterins also reduces the spread of salmonella in chickens via feces and eggs.

Some companies produce bacterin for commercial use.

Controlling rodents, insects and wild birds

Vectors are organisms that can spread disease. Vector control throughout your flock’s life is key to reducing salmonella.

  • Work routinely with a licensed professional rodent and insect exterminator.
  • Be sure that personnel practice strict biosecurity steps for their clothing, equipment and vehicles.
  • Make sure service providers have a good vector control record with poultry operations.


Rodent feces can contain infectious amounts of salmonella. Mouse feces, common in feed troughs, may amplify salmonella disease in poultry. Rodents also carry disease to near and distant houses and farms.


  • Remove all cover for rodents inside and outside the poultry house. This may include:
    • Shrubs or tall grass
    • Garbage or construction debris
    • Broken equipment
    • Burrows under the foundation
  • Set up a rodent barrier around the outside of the poultry house.
  • Seal all entrance holes inside and outside the building.
    • Fix and close siding sheet seams.
    • Make sure doors and door frames fit tight.
  • Seal holes and cement cracks in manure pits.
  • Make sure rodents don’t reside in reused filler flats, which can move to and from farms during egg delivery.
  • Secure feed bins and sheds at night. Clean up dead birds and broken eggs daily.

Print expanded content.

Caution: All baits are harmful to rodents, chickens, animals and people.

Preparing to bait
  • Remove all feed from feeders right after house depopulation, so rodents promptly go to the bait.
  • Remove all other food sources such as spilled feed, broken eggs and dead birds.
  • Check the outside of buildings often for rodent holes.
Selecting bait

Warfarin, diphacinone and pival are rat poisons that work by thinning the blood. To be effective, rats must receive these poisons in multiple doses over several days. Thus, poison works best if you use it routinely, every two weeks.

Newer blood thinners contain brodifacoum and bromadiolone. These may cause death three to five days after a single feeding. You can use single-dose rat poison at any time, especially right after house depopulation.

Make sure to stock enough rat poison to meet the long-term need of the farm.

Placing bait
  • Place baits to avoid contaminating feed and eggs or coming in contact with poultry and humans.
    • Don’t place bait loosely on the ground in high-traffic areas. People may carry it on their shoes and contaminate sensitive areas.
  • Save bait by only baiting holes with rodent activity.
  1. Fill all rodent holes with dirt or paper.
  2. Check for open holes later.
  3. Only bait the open holes.
  • Follow the manufacturer’s directions when placing the bait.
  • Control attic rodents by making a hatch for attic access and bait with a high-wax single-dose poison at least once yearly.
  • After controlling rodents, inspect and keep up permanent bait sites every two weeks. Record the location and numbers of trapped mice and maintain these records.

Print expanded content.


Using several practices to control insects reduces the chance of insects adapting to a single method.

For example

  • Keep manure well ventilated and dry.
  • Prevent water leaks and remove wet areas.
  • If possible, use biological control methods (fly parasites and predators).
  • Use different types of insecticides.

Applying insecticide

  1. Clean and disinfect the poultry house floor.
  2. Once the floor dries, apply an approved insecticide to the floor, support poles and walls.
  3. Always follow the manufacturer’s safety precautions.

You can use synergized pyrethrins (pyrethrin plus piperonyl butoxide) in automatic spray systems inside poultry houses. These quickly knockdown flying insects, have short residual times and have low toxicity in mammals. Don’t apply these insecticides more than twice weekly, especially if you use a spray system.

Wild birds and pets

  • Avoid feed spills outside the buildings and clean up any spills right away.
  • Buildings should keep out wild birds and prevent them from sitting under eaves or on blinds.
  • Keep pets out of pullet and layer houses.

Cleaning facilities

Always clean pullet and layer houses between flocks to reduce possible buildup of disease agents, such as salmonella.

Clean facilities as soon as you remove the birds if any tested positive for salmonella. Cleaning will prevent replacements from contamination.

Good cleaning programs need to:

  • Be put in place across the entire farm
  • Have proper equipment
  • Have professional training

Cleaning conventional facilities presents a big challenge due to the following.

  • Facility size and complexity
  • Wooden construction materials are harder to disinfect than smooth metal surfaces
  • Plastic and fibrous egg handling surfaces are harder to disinfect than smooth metal surfaces

These problems decrease how effective cleaning plans are. In the past, many used formaldehyde to help disinfect porous surfaces. Although effective against salmonella, its use comes with human safety concerns, poor product availability and regulatory policies. Other options may help disinfect porous surfaces.

  • Other fumigants
  • Heat-enhanced disinfectants
  • High-pressure sprays or disinfectant foams
  • Sealants to reduce the rough surface of wood

Step-by-step cleaning


Remove all dead and live birds from the building. This includes all escaped birds in the deep pit or outside. Start vector control procedures right away during bird removal.

Print expanded content.

  • Clean fans and other air inlets from the outside.
  • Moving from top to bottom, clean up the dust inside the building. For example, remove dust from the ceiling, beams, walls, cages etc.
  • Promptly open feeder lines and remove all feed including feed inside troughs.
  • Open egg conveyance equipment at the front of the building and remove all dust and egg debris. Remove broken and soiled parts that you can’t clean.
  • Do your best to remove manure from dropping boards.
  • Remove all litter and manure from floor or cage houses, including augers and pit ends.
    • Be aware of National Institute for Occupational Safety and Health alerts on manure pit hazards.
    • If you can, fill trailers with manure inside the house and cover it before hauling to a disposal or composting site. Manure should not be spread near poultry facilities.
  • Remove egg belts and sweep away all debris above and below the belt.
  • Remove all debris and items not needed from the entire building.
  • Turn off power to electrical equipment prior to cleaning. Use compressed air or brushes to clean non-removable motors, switches, etc. Take extra care to keep sprays out of electric motors. Use duct tape to cover the motor slots before wet cleaning and disinfection. Remove the tape after wet cleaning and disinfecting.

Print expanded content.

Soaking and washing
  1. Soften dirt in heavily soiled areas. Use a low-pressure (200 to 300 pounds per square inch) sprayer, which delivers 10 to 30 gallons per minute. Hot water and cleaners can help loosen debris and films that salmonella can grow in.
  2. While washing, start at the back and work toward the front. Spray the ceiling first, then the walls and lastly the floor. Thoroughly clean everything.
  3. Use sprayer attachments and nozzles that allow you to wash hard-to-reach places.
  • Aim for 750 to 2000 pounds per square inch.
  • High pressure requires extra care and safety clothing. Pressure sprayers can cut human skin like a knife. Always follow the manufacturer’s instructions for use.
  • Be sure to wash under the troughs and hidden surfaces of chains and augers.
  • Clean the egg elevator completely. Check that each angle (from under the pit and from behind rollers) is clean. Remove all traces of egg.
  • Wash storage and egg rooms, egg coolers, hallways, break, wash and restrooms.
  • Clean any other areas by hand if you haven’t cleaned them already.

A final rinse reduces residues of cleaning chemicals. Make sure to remove puddles right away to prevent bacteria from growing in them.


Make all repairs after rinsing including:

  • Filling floor cracks
  • Repairing door frames
  • Replacing damaged panels
  • Repairing manure, egg handling and other equipment
Dirt floors

Add 3 to 6 inches of clean soil to houses with dirt floor pits to decrease risk of disease in new flocks. We don’t know the value of this for preventing salmonella.

Print expanded content.

Have a third-party inspect your facility after wet cleaning and repairs. This may be done by an outside authority or by an in-house, unbiased employee in quality control.

Print expanded content.

Start disinfecting within 24 hours of rinsing. Disinfectants are only effective on clean surfaces.

Heat enhancement

All disinfectants work best at temperatures over 65 F. Temperatures for chlorine- and iodine-based disinfectants shouldn’t exceed 110 F.

Dangerous mixtures

Always follow the manufacturer’s instructions for human and flock safety. Avoid adding chemicals to disinfectants without manufacturer approval. Adding chemicals can dangerously reduce product efficacy.

  • Apply one gallon of diluted disinfectant to about 100 to 150 square feet of surface area.
    • To determine how much disinfectant you need, find the total surface area of the floor, ceiling and walls. Add 30 percent to this area to allow for cage surfaces.
  • Follow manufacturer instructions to apply disinfectants.
    • Use a pressure sprayer (500 to 1000 pounds per square inch) to help force disinfectants into wood pores and cracks. Move from back to front and from top to bottom.
  • Dirt floors are almost impossible to fully disinfect. Apply disinfectant to dirt floors at one gallon of diluted disinfectant per 10 square feet.
  • Disinfect egg handling equipment following equipment and disinfectant manufacturer recommendations.
    • Disinfecting egg belts using steam, vats of water at pasteurization temperatures, or soaking could help but efficacy or adverse effects on the belt aren’t known.
  • Clean feed bins, boots, augers, hoppers and carts. Sanitize water-lines.
    • Improper use of sanitizing agents can plug lines or damage metal and nonmetallic parts of watering systems.
    • Check with your farm’s water handling equipment manufacturer before using any specific chlorine or other treatments of your wells or water lines.
  • Promptly dry the building. You can use bullet space heaters to speed drying in cold or damp climates.
  • Test your facility for salmonella following disinfection. Make sure results are negative before placing chicks or ready-to-lay hens in your facility.
Formaldehyde and formalin

WARNING: Formaldehyde and formalin are dangerous chemicals. Always, contact state/federal (EPA, OSHA, FDA) authorities and licensed professionals before considering use. You will need gas masks, protective clothing and rescue plans when using these.

In the past, producers used formaldehyde (formalin) to disinfectant for salmonella. Producers also used formaldehyde fumigation (gas) as a final crack- and pore-cleaning step if relative humidity was at least 70 percent and temperatures were at least 70 F.

Print expanded content.

Preparations for restarting

  1. Replace disposable items with new ones (for example, sponges on egg conveyor equipment).
  2. Repair and adjust your egg handling and conveyance system from hen to cooler.
  3. Remove old water filters. Clean and disinfect casing and install new filters.
  4. Restock restrooms and portable toilets with soap and paper towels.
  5. Make sure that all electrical equipment work properly.
  6. Clean all equipment used for washing and disinfecting the facility and store them in a clean, secure space.

Monitoring bacteria

You must monitor bacteria through laboratory testing to complete your quality control program. Monitoring helps keep track of how well you’re reducing risk. Lawyers suggest that knowledge of a problem is better than none.

Collecting samples

Sampling often requires on-the-spot judgements. How you collect samples is more important than how many you collect. Poor sampling or laboratory methods can result in a false negative reading. Choose a laboratory that follows good salmonella culture methods.


You can sample numerous surfaces including:

  • Ceilings, walls and floors
  • Fan housings and blades
  • Cages
  • Waterers and feed troughs
  • Manure scrapers
  • Egg belts, rollers and sponges
How to collect samples

Use 33 or 44 inch multi-layered, lightly-moistened gauze pads. Gauze pads allow you to forcefully wipe large (22 foot) areas. A damp pad allows particles to stick better.

Only use cotton-tipped swabs for sampling hard-to-reach places.

Always wear sterile disposable gloves when sampling. Promptly refrigerate samples at 35 to 38 F.

Sampling of rodents is a prime sampling strategy.

Print expanded content.

Drag swabs are gauze pads connected to a cord that are drawn over droppings and litter. They produce results that reflect the salmonella gut carrier or organ infection status of chickens.

How to collect samples

Draw two gauze pads connected to cord over fresh droppings along the full length of each row.

  • Use one two-pad drag swab set per row in caged pullet or layer houses.
  • Drag two or three two-pad drag swab sets over the litter surface if you keep your flocks on litter. Draw the swabs over litter at pen ends, sides and center.
    • Make sure each two-pad drag has contact with the litter for at least five to six minutes.

Print expanded content.

Monitoring plans and schedules

State laws, regulations and policies differ on the privacy of voluntary monitoring to help gain research, disease and in-house quality control data. Positive results during any bacteria monitoring times (see table 1) may present complex fiscal, legal and ethical issues. The same may be true for if you don’t monitor. Work with professionals (legal, underwriter and veterinary) to develop monitoring programs and choose from the following examples for pullet and layer flocks.


Table 2. Examples of chick/pullet monitoring times, locations and purposes

Time/Age Location Purpose
0 to 1 daya,b Chick transport papers, chick feces, cull chicks and dead chicks Detection of breeder or hatchery transmitted salmonella
2 weeksc Dropping boards (cage reared) or litter surfaces (floor reared) Detection of infection after period of high susceptibility
10 to 16 weeks Droppings or drag swabs of manure (litter) surfaces Detection of infection prior to movement to layer facilities
2 to 3 days after decontamination (C & D) of pullet facility Building/equipment surfaces, fan blades, etc. Evaluation of C & D operation prior to housing new chicks

aA laboratory manual detailing sampling and culture procedures and a magazine update on culture media improvements have recently been published.

bAn additional test for salmonella in one-day-old hatchlings is described in the mentioned laboratory manual (Chapter 1, page 5).

cAt any age, bacteriological examination of culls, fresh dead, and trapped mice especially, are used to enhance detection efficiency.

Print expanded content.

Table 3. Examples of layer monitoring times, locations and purposes

Time/Age Location Purpose
10 – 12 weeks prior to depopulation of layer housea,b,c,d Droppings, or drag swabs of manure (litter), and building/equipment surfaces. Egg belts and elevators Fan blades Cages Walls Other Detection of infection with adequate time for decontamination (C & D) and vaccination of pullets
2 – 3 days after C & D 2 – 3 days after C & D Building/equipment surfaces as listed above Evaluation of C & D operation prior to housing new pullets

aA laboratory manual detailing sampling and culture procedures and a magazine update on culture media improvements have recently been published.

bUse of cull eggs and/or blood (serum) samples are currently being evaluated as additional or alternative monitoring tools.

cAt any age, bacteriological examination of culls, fresh dead, and trapped mice especially, are used to enhance detection efficiency.

dMore frequent monitoring during lay has also been suggested to increase the likelihood of prompt detection of contamination.

Egg handling


Protect eggshell strength

Salmonella can get into weak shells more easily. Avoid weak shells by:

  • Having properly formulated feed at all ages.
    • For example, supplement enough calcium and vitamin D3 levels.
  • Vaccinating for infectious bronchitis and Newcastle disease that weak the shell.

Gather eggs frequently

Eggs exposed to temperatures of 80 to 90 F promote bacterial growth and increase salmonella risk.

Properly wash eggs

In-line washing systems

Wash the eggs and cool to 45 F or less. Use only potable water with a maximum iron content of 2 parts per million and a minimum wash water temperature of 90 F.

Nest run systems

Cool the eggs right away to 60 F until you wash them. This will avoid cracks during washing. If the egg and wash water temperatures differ by 50 F or more, you may need to pre-warm the eggs before washing. Make sure the wash and rinse solutions are 10 to 15 F warmer than the eggs.

Use sanitizers following the manufacturer’s recommendations.

After washing, cool the eggs to 45 F or less if sweating can be controlled.

Provide good storage and transport temperatures

Eggs should remain at 45 F during storage and transport.

Control inventory

Rotate the product at all levels of distribution, warehousing, sale and home or institutional use. This inventory control decreases the likelihood of salmonella growth in the product.

Have proper food labels

State on egg carton labels that eggs are a perishable (will spoil) food and require the same care, including cooking, as other animal source foods. More informed consumers benefits both producers and their customers. Store eggs in their original carton in the main section of the refrigerator and not in the door shelf, where it can reach 60 F.

Don’t reuse fiber flats and egg cartons. Reusing these can save you money but they can lead to disease spread. Plastic flats are more ideal for reuse, but you must wash and disinfect them after each use.

Print expanded content.

Salmonella can contaminate both the egg shell surface and the inside of the egg. Salmonella contaminates the inside of an egg either before the egg fully forms or by entering the shell.

Proper egg washing and sanitizing can rid egg shell surfaces of salmonella but not salmonella inside the egg. Cool temperatures play a key role in preventing further salmonella growth inside eggs.

Egg white contains products that help kill or stop the growth of bacteria. These natural products become less effective as the egg whites age. Cool temperatures help slow egg white aging and thus, help it control bacterial growth.

Cold temperatures alone can also prevent or reduce the growth of salmonella organisms. Research shows that Salmonella enteritidis put into eggs, didn’t grow at 40 F, but did grow at 50 F. Thus, by reducing egg temperature to 45 F or lower, you can reduce the risk of salmonella growth.

Print expanded content.

Feed and water

Many salmonella types have been found in feed and feed ingredients. You must prevent salmonella contamination after manufacturing. Take care in selecting feed suppliers and in shipping and storing feed.


  • Obtain feed from mills that follow the guidelines:
    • Recommended Salmonella Control for Processors of Livestock and Poultry Feeds, published in September, 1988 by the American Feed Industry Association, 1501 Wilson Blvd., Suite 1100, Arlington, VA 22209.
  • Use animal protein ingredients from rendering plants taking part in the Animal Protein Producers Industry (APPI) Salmonella Reduction Education Program.
  • Keep feed ingredients and finished feed at all stages of manufacture and storage dry.

Print expanded content.

  • Keep rodents out of feed.
  • Keep feed dry.
  • Seek advice from your nutritionist and veterinarian before using anti-salmonella feed additives.
    • These differ in effectiveness and mode of action and may be subject to Food and Drug Administration (FDA) regulatory control.
  • Start your own bank of feed samples.
    • Feed banks and testing promote quality control.
    • Store samples in a clean, dry place at room temperature.

Print expanded content.

Competitive exclusion (CE) refers to the natural gut bacteria that protect the bird from pathogens. You can buy and feed CE to your flocks.

Prompt post-hatch founding of CE gut bacteria, with a clean environment, may help reduce the risks of salmonella growth in the gut of normally prone, young fowl. CE cultures seem to help speed the growth of a possible protective gut bacteria. Probiotics aren’t quite the same as CE cultures.

Print expanded content.

Routinely chlorinating poultry drinking water to at least 1 to 1.5 parts per million of free chlorine level reduces the spread of salmonella.

Print expanded content.


Biosecurity practices that prevent most diseases are equally good within a salmonella risk reduction program. Salmonella infects flocks when a virus or disease agent weakens your flock’s natural defense. Thus every step in biosecurity is an investment in flock survival.

People can also aid in spreading salmonella to chickens and eggs. Thus, all farm workers must have good hygiene. Provide clean, working toilets with hand washing and drying facilities to serve all employees.

Provide training materials such as videos or pamphlets to employees at all levels. Review such materials regularly and add practices as you see fit for your farm.

Biosecurity checklists

Checklists for flock caretakers and farm managers

Flock caretakers

You can post this list in all poultry houses. Consider printing large, clear posters.

  • Watch for, correct and report right away any rodent, insect, wild bird or pet problems.
    • Rats and mice are especially important!
  • Check daily for quick, secure removal of all dead and dying birds.
  • Have disinfectant soap available for personnel handling chickens or eggs.
  • Don’t go into the poultry house after hunting.
  • Keep egg belts, elevators, etc. in proper adjustment. Regularly clean and sanitize.
  • Wear clean clothing.
Farm managers
  • State in contracts and check that all pullet deliveries are made in clean and disinfected coops and trucks.
  • Make sure all visitors, farm executives and others wear biosecure clothing.
  • Ban caretakers from having any poultry flocks at home.

Spent hen removal

  • Make sure all racks are clean before they enter the poultry house.
  • Be sure the driver dresses in clean clothing before going into the poultry house.

Kim, C. J., D. A. Emery, H. Rinke, K. V. Nagaraja, and D. A. Halvorson. Effect of time and temperature on growth of Salmonella enteritidis in experimentally inoculated eggs. Avian Dis. 33:735-742. 1989.

“Biosecurity for Poultry Lock Diseases Out.” 1987. (Brunet).

Diseases of Poultry. Ninth ed. 1991. Chapter 30, “External Parasites and Poultry Pests.” (J. J. Arends). Pp. 727-730.

1991 United States Animal Health Association Salmonella Committee “Integrated Guidelines for Table Egg Producers” with input from members of the Minnesota Poultry Industries Association.

David Halvorson, emeritus professor, College of Veterinary Medicine