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Johns Hopkins Bloomberg School of Public HealthCAAT

Animal Welfare Enhancement Awards - 2004 Recipients

Investigate the Use of Enrichment Materials (EMs) by Research Animals as an Indicator of Pain and Distress
Kinta Diven, Patricia Matos, Michelle Browning DVM, Malu Mooney, Antonio De Maio Ph.D., James Owiny, BVM Ph.D.
 The Johns Hopkins University


My objective was to investigate the use of Enrichment Materials (EMs) by research animals as an indicator of pain or distress. A component of my objective was to determine whether the use of EMs can be measured without a significant increase in the workload or the need for elaborate expensive monitoring equipment. Labor intensive monitoring will not be useful to most investigators. My long-term goal is to evaluate the use of EMs to enhance the use of chemical analgesia and in some cases, maybe even replace it.

Part One:

Evaluation and Selection of Enrichment Materials Untreated mice were provided both non-food and food EMs such as nesting material, paper tubes, plastic tubes, cardboard houses, seeds, pelleted treats, etc. The mice were housed individually and each mouse received the test EM. The use of the EM was observed three times a day for three days. The EM selected for part two was based on the ability to observe and measure the use of the EM by the mouse. These activities (i.e. shredding, moving, consuming) were scored on a scale of 0-100 percent. Expense and availability were also considered. Based on the data gathered during the EM evaluation period the Nestlet™ was chosen as the enrichment material to be used for part two of the study. This study indicated 95% of the mice tested engaged in the use of the Nestlet™.

Part Two: Evaluation Of Changes In The Use Of The Enrichment Materials By Post-Surgery Mice.

Animal used in this part of the study underwent abdominal surgery. After anesthesia and proper surgical preparation the abdominal cavity was opened and macrophage cells collected by flushing with saline. Prior to the surgery the mice were group housed. Upon completion of the procedure the mice were singly housed, treated with analgesia, and the Nestlet™ was placed on the wire bar of the cage. This way the mouse had to stretch up to pull the Nestlet™ down into the cage to make a nest. Each morning for three days the mice and feed were weighed, the use of the Nestlet™ was scored, all portions of the Nestlet™ was removed, and a new Nestlet™ put on the wire bar.

In order to generate more statistically significant results the post surgical Nestlet™ evaluation was repeated three times on three different groups of mice. The third time the procedure and evaluation went smoothly. There were four groups in this part of the experiment. Group I underwent surgery, received chemical analgesia, and post-operative Nestlets™. Group II underwent surgery and received Nestlets™. Group III underwent surgery and received the chemical analgesia. Group IV received the Nestlets™ only.

The preliminary evaluation of the data indicates some interesting results. 1) The mice that underwent surgery and received Nestlets™, but no post operative analgesia, lost less weight and consumed more food than groups with analgesia. 2) The groups with out analgesia interacted with the Nestlet™ more than the groups with analgesia. 3) Providing enrichment in conjunction with analgesia had little effect on food consumption or weight loss compared to the group with analgesia only. 4) The group that received enrichment only consumed significantly more food on day three than days one or two. 5) All groups that received enrichment interacted with it more by day three than days one or two.


Nestlets™ were not a useful dictator of post operative pain or distress. However Nestlets™ did have a positive effect on the animal's recovery when analgesia was not used. The animal's use of the Nestlets™ was easy to evaluate and not time consuming. Also there was some indication that moving mice from a group housed environment to a single housed environment resulted in an adjustment period with less feed consumption and less Nestlet™ use.