Rodents are a potential source of Salmonella contamination on egg farms, and keeping the number of rodents as low as possible is an important part of any Salmonella prevention program. High-rise, or deep pit houses, are particularly problematic for rodent control because the manure stored in the building can provide nesting space or harborage for mice and rats. While rodent control maybe more difficult in high-rise houses, it isn’t impossible, according to Dr. Maxcy P. Nolan, Jr., consulting entomologist, NIPCAM Group.

Nolan told the audience at the United Egg Producers' board meeting in Atlanta that some farms have dramatically reduced rodent numbers in deep pit houses, but it takes a real commitment to getting the job done.

Every egg farm needs to have a documented rodent control plan that meets all the requirements of the Egg Safety Rule. Nolan said to make sure that the plan does in fact meet all of the requirements, and that producers do exactly what the plan calls for, documenting everything. Producers need to establish who is going to “own” the various steps of pest control, and that there needs to be “buy in” of the program by management/ownership of the farm.

Rodent index  

The rodent index is based on the number of rodents caught in functional traps; Nolan stated that producers need to make sure that their traps work, and replace the ones that don’t work. “People are going to get in trouble for having traps that aren’t functional when an inspector comes out,” he said. “This worries me.”

Nolan said that egg farms can dramatically reduce the number of rodents on the farm, but that it is very difficult to completely eliminate them. “What is the goal? Zero is a great goal, but I am trying to get a rodent index of one,” he said.

Start with inspections  

In order to control rodents, producers have to know what pests they have and where they are, and the only way to know these things is by inspecting the facility. “You need to put on your pest management hat and do your inspections,” Nolan stated. “It is important to do this and take it seriously.”

When inspecting farms for rodents, Nolan suggested to bring a flashlight, digital camera and a diagram of the facility. The flashlight is needed to see in dark areas, the camera is for documentation, and the diagram should be marked to show where the pictures were taken. “You have to know where your problems are so you can make a plan to fix them,” he said.

Rodents gnaw and chew constantly, so Nolan said to look for signs of where they are gnawing. Look for burrows, because both rats and mice can dig burrows. Look for runways and grease marks.

Rodent urine fluoresces under ultra violet light, which can be used to spot urine stains. “As you do a better job with rodent control, it gets harder to find them, and having an ultra violet light can help,” Nolan suggested.

It is important to know which types of rats or mice are present on the farm. The control measures vary somewhat depending on the type of rodent. For instance, Nolan explained that it takes more poisoned bait to kill mice than it does rats.


Farm sanitation plays a role in rodent control; on each inspection tour, egg producers need to pay attention and be prepared to document and correct any problems with overgrown vegetation, equipment left outside buildings or any other debris. “Food, shelter, trash and vegetation are things that we find on the farms all of the time,” Nolan said. Vegetation needs to be cut around and between houses, and no old equipment should be stored between houses. Rodents need food and harborage, and both can be found in between houses if junk and vegetation are allowed to accumulate.

Clean out the house and the rodents  

“If you want to start as close to zero in rodent numbers as you can, then you need to have 14 to 21 days of downtime between flocks,” Nolan stated. This is particularly important for farms that have too many rodents. Clean out is the best time to gain control of a rodent population, and it is best to clean out the manure and the birds at the same time.

“You need to clean out the manure, kill the rodents and fix any holes in the building,” Nolan said. “You need to have your building materials to patch up the house on hand when the birds are loaded out. You need to start baiting the rodents as soon as you start taking the birds out.” When patching holes in the building, make sure that the fix is something that is going to last.

Baits are a necessity  

“You are not going to be able to reduce a large rodent population with trapping,” Nolan said. “Trapping is good for monitoring, but you need to use baits to reduce a large population.”

Nolan said that he likes to give rodents a choice of baits that are in different forms, like pellets and bars. These baits will have the same active ingredient and may even be the same brand, but presenting the rodents with choices will get them to consume the poison.

Rotating baits is important because of resistance issues. When baits are switched, Nolan advises checking to make sure the new bait uses a different active ingredient. Remember that different brands can have the same active ingredient.

“In situations where we can’t get to the rodents easily with rodenticides, we have had good success with tracking powders,” he said. These powders can get deep into harborage areas. Tracking powders have active ingredients that are restricted use pesticides, so Nolan suggested getting someone on staff certified to apply these, giving egg producers another weapon in the rodent control arsenal. “Don’t bring a BB gun to a deer hunt; you have to be prepared and bring the right materials,” Nolan said.

The two major categories of rodent control substances are neurotoxins, which kill in hours, and anticoagulants, that kill slower. Nolan said that the neurotoxins are good for when egg producers really need to get rodent numbers down, and that the anticoagulants are good for a regular control program.