There’s no doubt among egg producers that house mice, Norway Rats and roof rats can be a major problem in and around egg production facilities. Disease transmission, feed loss, bird stress and property damage result in significant monetary losses for the producer.

Effective rodent control is a necessity, which requires an investment of time and money. But here’s some good news: A little knowledge can go a long way toward reducing overall rodent-related costs. It is important to understand the pest’s behavior, and then use that knowledge to select the most effective tools to control them.

Get off on the right foot

Reducing rodent control costs starts with the concept that rodent control is a “process” and not a “program”. A program has a distinct beginning and an end. Rodents are a never-ending threat so your control efforts must also be never ending. A rodent control process must be an integral part of your production process.

Achieving “zero mice” may not be practical, or even possible, for several reasons. First, rodents are very prolific creatures. A single female house mouse, for example, may produce up to 56 offspring annually. Also, new rodents are constantly drawn to egg production facilities as a source of food and warmth. In addition, rodents are excellent climbers and can squeeze through tiny openings or create their own. In other words, sealing a house to exclude rodents is a difficult prospect at best. What’s more, these critters are nocturnal and most of their activity goes unseen.

Too often an egg producer will implement a rodent control program when the infestation becomes serious and end it when the infestation is no longer at crisis level. This approach allows significant risk of rodent-related losses. It also requires a larger investment in time and money to knock down that large population of rodents than it does to keep rodents under control in the first place.

Know your rodenticides

Rodenticides have proven to be the most cost-effective method of rodent control when compared with traps and other methods. There are two groups of rodenticides commonly used in egg production facilities: acute toxicants and anticoagulants. Understanding each will lead to a cost-effective approach.

Acute toxicants are rodenticides with active ingredients such as zinc phosphide, cholecalciferol and bromethalin. If a lethal dose is ingested they can kill quickly. However, the high concentrations of active ingredients in these products tend to make them taste bad so if there is a competing feed source available, rodents may not eat enough of the bait to be lethal. Rodents exposed to these materials exhibit signs of distress such as paralysis and convulsions. If less than a lethal dose is ingested the rodent will experience these distressful symptoms of poisoning and associate the recently eaten bait to its discomfort and avoid that material in the future. This is commonly referred to as “bait shyness”. It is also important to note that young rodents take clues from their mother about which feed sources are safe to eat.

The other group of rodenticides is referred to as anticoagulants, of which there are single-feed and multiple-feed formulations. Anticoagulants inhibit the blood clotting mechanism, causing rodents to die from internal bleeding. The process produces no signs that the rodent is in distress or pain. Single-feed anticoagulants contain active ingredients at much lower concentrations than the acute materials, so bait acceptance is much better. Multiple feed anticoagulants may take a week or more to be effective. Single-feed anticoagulants are effective within several days, which is still relatively fast, but not so fast as to trigger bait shyness.

Use the right mix

Both acute and anticoagulant rodenticides have their place in a rodent control process. Using the right mix of rodenticides in a “rotation strategy” is the most practical approach and one that saves money in the long run.

Acute toxicants are best suited for a quick knockdown of an infestation during cleanout. Eliminate as many competing feed sources as possible to enhance the acceptance of the bait. Don’t rely on them too long in order to prevent “bait shy” survivors and their offspring from reestablishing the infestation.

After clean-out, rotate to highly palatable anticoagulant rodenticides. Rotate the use of different tasting materials to kill survivors who chose not to feed on one bait choice or the other.


In short, the key is to knock down a rodent population and keep it down through the use of a rotation strategy. This will reduce rodenticide costs, labor costs, and the risk of disease outbreaks as rodents travel from house to house.

Look deeper in the bucket

When choosing rodenticides, cost reductions can also be realized by doing some math. A common misperception is that the least expensive rodenticide is the most cost-effective solution. But reality says otherwise,R and there are several factors to consider.

The first cost factor to consider is the “cost per placement” of the rodenticide used. Simply put, how many blocks or “placements” of bait are there in a pail of rodenticide.

An investment in rodenticides can also yield higher returns when the number of rodent kills per placement is factored in. Determining the number of kills (or cost per dead rodent) requires an understanding of the active ingredients involved. Some active ingredients are more toxic than others, so they can produce more kills per placement.

Don’t forget the basics

Adhering to a few fundamental principles will also reduce the total cost of rodent control:

• Understand the rodent. Mice behave differently than rats and roof rats behave differently than Norway Rats. A program cannot be successful unless control methods match the behavior of the rodent involved.

• Select the right formulation. Block types are best for mice. Avoid using pellets for mice, as they will hoard them, wasting materials and creating risk. Loose pellets or meal-type baits are excellent for Norway Rats because they can be spooned directly into their burrows in the soil. Blocks are great for roof rats because they can easily be secured up high where this pest lives and travels. Make sure the product label allows the application you are considering.

• Place the material in the right place. Generally, this is as close to the rodents’ nest as possible, but certainly between the nest and feed source. Improperly placed material wastes time and money.

• Use enough rodenticide. The number one cause of rodent control failure is using too little material. There must be enough available to allow every rodent to feed on it. Some will get more than enough to kill them and more than their share, while others may be denied a lethal dose. They will survive and repopulate quickly.

• Manage the risks. Doing nothing, or too little, has risks such as disease outbreaks and damage to the house. All rodenticides also have risks, which must be managed. Properly contain rodenticides within tamper-resistant bait stations, in all areas accessible to children and non-target animals.

Adding it up

Rodent control is an ongoing process that requires an investment in time and money. The key is in understanding rodents and rodenticides and then sharpening the pencil. After weighing the pros and cons, move forward with an approach that delivers the best return for the dollar. EI