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Using the right type of mouse bedding and enrichment for your lab is crucial to cleanliness, animal welfare, and accurate results.

There are many important factors in the conducting of a mouse study, including the choice of bedding used in the cages and the addition of enrichment items. Bedding and enrichment compose the majority of the animal’s environment and can play an influential role in its development; thus, an educated selection is critical in optimizing both the welfare of the mouse and the output of the study.

Cage bedding must be able to absorb liquid discharge and prevent ammonia buildup. It should be comfortable for the animal, simulating a natural environment in which the mouse can burrow and nest contentedly. To avoid accidentally introducing unwanted variables, it should be dust-free and standardized across cages. Enrichment items should also facilitate natural chewing, tearing, and/or nesting behaviors.

What you put into your mouse cages are what they have to live in —so choose wisely.

Woodchip Bedding
Labs have been using woodchip bedding in mouse cages for decades. The most “natural” of bedding types, woodchips are similar to material mice burrow under and nest with in the wild. This classic style of bedding is naturally absorbent and offers strong ammonia control. In addition, woodchips are among the least expensive of bedding types, well-suited for facilities on a tight budget.

ProChip wood bedding from PWI Industries is available in aspen and maple varieties. Clean, dry, sterile, odor controlling, and economically priced, ProChip is reliable for researchers and their mice, says John Samson of PWI. “Normally, it is cheaper bedding in price,” Samson says. “But people don’t buy it for the price — they buy it for the product.”

“The woodchip was the pioneer in mouse bedding…It benefits the welfare of the animal, to be in more of a natural habitat.” Samson added.

PWI also offers treated aspen Chew Sticks enrichment items. The hardwood aspen does not produce dangerous splinters, and gnawing on a Chew Stick mimics actions that mice would have in the wild.

Cob Bedding
Bedding made from dried corn cobs is highly absorbent, biodegradable, and easy to incinerate. Cob bedding can absorb at least five times its weight in moisture, so well that it has been used to help clean up oil slicks. The cellulose structure of corn cobs traps ammonia crystals when the water component of urine evaporates. The smaller the cob is sliced, the more cumulative surface area the bedding has, and the better it will absorb moisture.

Bed-o’cobs corn cob bedding, manufactured by The Andersons, Inc., is available in quarter-inch, eighth-inch, and half-and-half varieties, to suit different budgets, researcher preferences, and sizes of mice. This heat-dried bedding is subjected to regular independent analysis. The Andersons, Inc. also offers variants on bed-o’cobs, including irradiated versions, and Enrich-o’cobs, which packages paper rolls for enrichment and nesting along with the cobs, eliminating the necessity of adding enrichment manually.

“We are looking for products that are going to provide a combination of features into one that will be more labor-saving,” says Jerry Reynolds, national sales manager for The Andersons, Inc. “That means combining bedding, enrichment, and nesting. You need all three of those things, and we try to combine those things in a way that will save labor in the lab.”

Shepherd Specialty Papers, though specializing in paper and cellulose bedding materials, offers Shepherd’s Cob, which is heat-dried to a low of 5%moisture content for maximum absorbency and better elimination of bacteria. It comes in quarter-inch and eighth-inch versions, as well as a version with rolled-paper enrichment for mice to tear apart and nest with, called Shepherd’s Cob +Plus. Shepherd also sells all its products by weight to guarantee consistency of quantity.

Paper/Cellulose Bedding
The most consistent bedding in terms of content can be found in paper and cellulose brands, which are engineered to eliminate variables while still offering absorbency and ammonia control. Because of the manufacturing costs, these beddings are usually the most expensive, but critical to high-precision studies in fields like toxicology. Because of their typically bright white color, these beddings are also easiest for observing animal discharge if required.

CareFRESH wood-pulp bedding from Absorption Corp is made from virgin wood pulp and is engineered to suppress ammonia formation; CareFRESH Ultra uses long-fiber, high-grade white pulp for easy observation of discharge. Both beddings are fluffy and serve as partial enrichment themselves, encouraging natural behaviors like foraging, nesting, and burrowing.

“It eliminates the need for shred-able pads or housing, [which] provides fewer variables in your animal study,” says Tom Pletcher, director of marketing for Absorption Corp. “It is only bedding [to us]; however to the animal it is their entire world, from bathroom to living room to procedure recovery room to birthing center, and many more rooms along the way.”

ALPHA-dri bedding and associated products are the signature creations of Shepherd Specialty Papers. Made from alpha cellulose and manufactured in extremely absorbent particles of uniform size, ALPHA-dri is available in several varieties, including irradiated and blended with Shepherd’s Cob. It is essentially dust-free and static-free —easing dispensing and preventing clogs.

Company owner Joel Shepherd prides himself on ALPHA-dri’s consistency of composition and elimination of variables. “If change matters, you should use bedding that never changes,” Shepherd says. “Our industry has lost that over the past several years. They just don’t worry about the cleanliness of bedding material. Everything else comes secondary.”

The Andersons, Inc. produce a paper bedding in the form of Pure-o’cel, paper bedding chips that offer a high amount of surface area (increasing absorption); their soft and dust-free traits make it suited for hairless mice. The company also offers a blend of Pure-o’cel with its bed’o-cobs, and bedding designed for breeding mice, Enrich-n’nest, which includes paper rolls that serve as bedding, enrichment, and nesting all in one.

Enrichment
Enrichment of some sort is standard in improving the health and welfare of your mice, not to mention improving the results of your experiment.Most companies that offer bedding will also offer some form of enrichment (often combined with the bedding), but additional products can be utilized to better your animals’ experience.

With the double purpose of adding enrichment while reducing labor,W. F. Fisher and Son offer Nestpaks: a large teabag-style container pre-filled with an exact amount of bedding. The bags are placed in cages, and the mice tear them open to get at the material inside—they essentially make their own bed. The product thus improves lab ergonomics and provides enrichment for the mice. A similar effect is found with the company’s new Rodent Foraging Box, stuffed with 6 grams of nesting-friendly bedding.

“[Our products] are best suited for large facilities that do not have automatic dispensing, and small facilities that are looking to cut labor costs by improving efficiencies,” says Joseph B. Bellomo of W. F. Fisher and Son.

Mice can also contribute to their own health — while engaging with enrichment — in using MiteArrest, permethrin- treated cotton that effectively destroys mites as the rodents tear, spread, and nest with the cotton. Instead of costly spray or spot treatments, the mice do all the work themselves, and a six week treatment eliminates all mite infestations.

“What sets MiteArrest apart from the rest is that instead of having to treat each animal individually and add a time consuming extra step specifically for mite control, one can simply add MiteArrest to bedding materials and allow for the natural nesting instinct of the rodent to do the work of killing mites,” says MiteArrest spokesperson Ariana Ganak.

Conclusion
Take measure of the full range of products available before selecting the bedding for your next experiment. Consider both your budget and your specific test related needs. Using the right bedding both adds value to research at the cage level and improves the welfare of your mice. Choose wisely; your research and mice are counting on it.

Darren McRoy is a freelance contributor to ALN Magazine. He can be reached at editors@alnmag.com