Rodgers, J. C., Ricart Arbona, R. J., Lieggi, C. et al. 2020. Evaluation of cotton dental rolls as environmental enrichment for mice. Laboratory Animal Science Professional 8(5) (September/October), 70-71.

Historically, we provided 2 compressed cotton squares for nesting and enrichment. The logistics of managing nesting material distribution, disposal, and costs are major considerations for our program, which provides husbandry to approximately 60,000 rodent cages weekly. We identified cotton dental rolls as an alternative, cost-effective nesting material with the potential for improved enrichment, while also being easier to distribute. A trial was conducted to determine if mice can use a cotton dental roll to make nests of the same or better quality when compared to 2 cotton squares (Phase 1) and to assess whether dental rolls are easier and faster to distribute (Phase 2). Dental rolls can be purchased in various lengths and diameters. A single 3pt dental roll provides 0.68 grams of fibrous material and is of similar weight to 2 small cotton squares that provide 0.6g of fibrous material. The dental rolls are packaged in groups of 50 rolls in easily removable paper sleeves. The study was conducted in phases. In Phase 1, we placed either a single 3pt dental roll or 2 cotton squares in 70 cages. Nest quality was assessed by a single trained observer 1, 2, 7, and 14 d after placement using the scoring system. Nests were transferred to a clean cage on day 7, the day of weekly cage change. Phase 2 was conducted as 3 distinct trials (2a, b, and c), each with increasing number of cages. This phase of the study was conducted to determine if the cotton dental roll was easier and faster to distribute than the cotton squares and to ensure there were no unexpected issues when implemented in a larger number of cages, housing a greater number of strains of cages, serviced by a larger team of technicians. The mean nest quality score over the 2-wk period for nests built using either 1 cotton dental roll or 2 cotton squares was 2.3 and 2.5, respectively. A small percentage of mice took more than 48 h to build a nest from a dental roll as compared to 2 cotton squares, which took less than 48 h. Feedback from 2 cage wash technicians indicated that the dental roll product was easier to distribute than the 2 cotton squares because they could grab a packet of 50 dental rolls straight from the bag in which they were delivered and easily remove the encasing paper before dispensing the rolls, rather than having to pull apart the sheets of cotton squares before dispensing. In the first week of Phase 2c, room technicians identified 9 adult mice that had leg strictures associated with tangled cotton dental roll fibers some associated with limb amputation. The trial was immediately discontinued. It appeared that the length of the fibers, along with their resistance to breakage (tensile strength) contributed to stricture formation. While cotton dental rolls are a suitable alternative to cotton squares from a nest building and cost and logistics standpoint, they cannot be recommended for use due to the adverse health events observed.