Griess, R. S. 2011. Environmental enrichment improves fertility and pup survival. Tech Talk [The Newsletter for Laboratory Animal Science Technicians] 16(1), 2-3.

Historically, we have added approximately half a cup of shredded aspen bedding for nest making into each littering cage. This procedure was continued as we looked into additional environmental enrichment. There are many types of environmental enrichment available on the market, including various reusable or disposable shelters and toys. What best met our needs was a shelter or toy that could be added to the animal cages, transferred at cage change, and sanitized for reuse. One item that fits into this category is a 3-in. length of PVC pipe (1.25 in.diameter). This inexpensive and readily available enrichment device serves several purposes, including a place for the mouse to hide in, chew on, and climb over. One tube was placed into each cage of this low-productivity colony when the mating cage was set up (with one male and two females) at age 12 weeks. The dams also had an enrichment tube added to the littering cages when separated from the sire at day 16 after initiating mating. At that time, the shredded aspen bedding was also added to the littering cage. The results were dramatic, as shown by the table at left. The addition of environmental enrichment caused dramatic changes in the performance of this colony. The number of unbred females dropped dramatically, from 4 and 11 to 0 and 1 per generation. The percent of viable litters jumped from 43% to 68% to over 90%. This increase in fertility and pup survival continued in the following generations as well. Although the comparison of enriched versus nonenriched cages were over different generations in the colony, the overall environmental conditions (room, temperature and humidity, light:dark cycle, feed and water type, bedding type) were kept constant. After analyzing these results, we decided to add this same environmental enrichment to all of our mouse cages. It has kept our breeding program successful throughout our facility. Additional benefits we have observed from this enrichment include a reduction in fighting between males at cage change and calmer behavior in individually housed animals.