Editor’s note: This tip was contributed by Roy William, member of the Dairy Calf and Heifer Association.

Mice can cause extensive damage to dairy operations in several ways. Over time, mice can cause serious structural damage to wooden barns. Mice will eat stored feed. They will eat large amounts of bagged milk replacer. Mice will get inside electrical boxes, damaging wiring and expensive electrical equipment, occasionally causing power outages, and even building fires. Mice will do significant damage to most types of insulation, including foam and fiberglass insulation. Mouse nests can cause malfunctions in mechanical equipment. Mice can cause objectionable odors in confined areas. Mice can multiply rapidly: in nine months one pair of mice can produce 600 offspring (in four generations) under ideal conditions.

Probably the greatest danger presented by mice is the transmission of diseases, primarily through droppings and urine that contaminate commodity storage areas and feed bunks. Some of the more significant cattle diseases carried by mice are leptospirosis, salmonellosis, and cryptosporidiosis.

Mice need water, food, and a nesting site. A nesting site is nearly any small secluded and protected location, often under some object, or inside a hollow wall, or in building insulation. Mice can chew through nearly anything except steel. They also do serious damage to barn roof insulation; if you have an insulated roof that is deteriorating the cause is likely mice (the common belief is that birds are the cause, but this may not be true - the birds just utilize what the mice have already done). Mice are seldom seen because they move primarily at night.

Mice do not travel very far from their nest - most references suggest 30 to 50 feet and they can make a vertical jump of 12 inches. Mice can climb vertical walls that have a rough textured surface, and they can travel along utility wires and fence wires. Mice can crawl through a hole that is less than .5 inch wide; some references claim mice can go through a .25 inch wide opening.

Putting all of these facts together suggests that the permanent way to keep mice away is to carefully eliminate all potential nesting sites, either directly or by eliminating access to those sites.  For example, silage bags should be set in large cleared area, free of vegetation and debris. Keeping the bags at least 50 feet from the nearest uncleared area will keep mice out. However, any mice that get into the area by riding on equipment, or are chased into the area by dogs or cats, will nest under the edges of the silage bags and a mouse population explosion can follow.

There are many aspects of mouse and rat control. Follow these four steps to begin your mice control program:

  1. Mouse-proof your buildings.
  2. Get rid of potential nesting areas.
  3. Implement a population reduction program.
  4. Eliminate water and food sources.

These on-line sources offer detailed information about control of rats and mice:

Ontario Ministry of Food and Agriculture Rodent Control in Livestock and Poultry Facilities

University of Florida Rat and Mouse Control

University of California Davis, Pests of Homes, Structures, People, and Pets, House Mouse

University of California Davis, Pests of Homes, Structures, People and Pets, Rats

Source: Dairy Calf and Heifer Association