Workaholic ferrets: Does a two-chamber consumer demand study give insight in the preferences of laboratory ferrets (Mustela putorius furo)?

Although provision of environmental enrichment is an effective tool to refine laboratory animal experiments, it is currently unknown which enrichments ferrets prefer. This study aimed to assess the suitability of a closed economy, two-chamber consumer demand set-up to determine ferrets’ preferences for selected enrichments. Twelve female ferrets were housed in a set-up consisting of a home and enrichment chamber (EC) connected by a weighted door. The maximum weights the ferrets pushed for food (MPPfood) and an empty chamber (MPPempty) were determined to evaluate the maximum push capacity of the animals and as a control. Although the ferrets pushed significantly more for food (1325 ± 213 g)than for the empty chamber (1169 ± 193 g), the weight difference was minor (MPPempty was 89 ± 13% of MPPfood). To evaluate the ferrets’ underlying motivation to push for the empty chamber, a second study was performed in which MPPempty was tested in seven alternative set-ups. The first three set-ups included adapted versions of the standard design (set-up A1, A2and A3), intended to determine the functional value of the empty chamber. The four other set-ups (set-up B0, B1, B3, B4) aimed to evaluate the attractiveness of the door elements by allowing the ferrets to choose whether or not to use the weighted door to enter EC. Results demonstrated no significant differences in MPPempty between the A-set-ups, indicating that the value of the empty chamber could not be reduced by adapting the set-up. MPPempty reduced when allowing the ferrets free access to EC, demonstrating that the empty chamber had reinforcing proper-ties. Nevertheless, the ferrets were still motivated to use the weighted door despite being granted free access to EC, indicating that the door also has reinforcing properties. The ferrets decreased the use of the weighted door most when, in a set-up with free access to EC, the nest box in the home cage (53 ± 22% of MPPfood) was replaced by a manipulable plastic bucket (26 ± 13% of MPPfood). These results indicate that availability of items in the home chamber may influence the results, which should be taken into account when designing motivation studies similar to the one performed in this study. The lack of differences between MPPfood and MPPempty furthermore demonstrates that the two-chamber set-up is not suitable for evaluating the ferrets’ motivation for enrichments, thus necessitating other alternatives, such as at three- or multi-chamber consumer demand study, to be explored

Workaholic ferrets: Does a two-chamber consumer demand study give insight in the preferences of laboratory ferrets (Mustela putorius furo)?

Although provision of environmental enrichment is an effective tool to refine laboratory animal experiments, it is currently unknown which enrichments ferrets prefer. This study aimed to assess the suitability of a closed economy, two-chamber consumer demand set-up to determine ferrets’ preferences for selected enrichments. Twelve female ferrets were housed in a set-up consisting of a home and enrichment chamber (EC) connected by a weighted door. The maximum weights the ferrets pushed for food (MPPfood) and an empty chamber (MPPempty) were determined to evaluate the maximum push capacity of the animals and as a control. Although the ferrets pushed significantly more for food (1325 ± 213 g)than for the empty chamber (1169 ± 193 g), the weight difference was minor (MPPempty was 89 ± 13% of MPPfood). To evaluate the ferrets’ underlying motivation to push for the empty chamber, a second study was performed in which MPPempty was tested in seven alternative set-ups. The first three set-ups included adapted versions of the standard design (set-up A1, A2and A3), intended to determine the functional value of the empty chamber. The four other set-ups (set-up B0, B1, B3, B4) aimed to evaluate the attractiveness of the door elements by allowing the ferrets to choose whether or not to use the weighted door to enter EC. Results demonstrated no significant differences in MPPempty between the A-set-ups, indicating that the value of the empty chamber could not be reduced by adapting the set-up. MPPempty reduced when allowing the ferrets free access to EC, demonstrating that the empty chamber had reinforcing proper-ties. Nevertheless, the ferrets were still motivated to use the weighted door despite being granted free access to EC, indicating that the door also has reinforcing properties. The ferrets decreased the use of the weighted door most when, in a set-up with free access to EC, the nest box in the home cage (53 ± 22% of MPPfood) was replaced by a manipulable plastic bucket (26 ± 13% of MPPfood). These results indicate that availability of items in the home chamber may influence the results, which should be taken into account when designing motivation studies similar to the one performed in this study. The lack of differences between MPPfood and MPPempty furthermore demonstrates that the two-chamber set-up is not suitable for evaluating the ferrets’ motivation for enrichments, thus necessitating other alternatives, such as at three- or multi-chamber consumer demand study, to be explored

Average percentage of ferrets (<i>N</i> = 19) that were assigned score 0, 1, and 2 for each of the AUs in the FGS by 11 observers at different time points.

<p>a) <i>orbital tightening</i>, b) <i>nose bulging</i>, c) <i>cheek bulging</i>, d) <i>ear changes</i> and e) <i>whisker retraction</i> on six time points relative to the time of surgery (T₀), * = score is significantly different from score on T_B2, # = score is significantly different from score on T_B5 with p<0.05 (11 observers, 19 ferrets).</p

The composition and initial evaluation of a grimace scale in ferrets after surgical implantation of a telemetry probe

<div><p>Reliable recognition of pain is difficult in ferrets as many currently available parameters are non-specific, inconsistent and/or impractical. Grimace scales have successfully been applied to assess pain in different animal species and might also be applicable to ferrets. To compose a Ferret Grimace Scale (FGS), we studied the facial musculature of ferrets and compared lateral photographs of 19 ferret faces at six time points before and after intraperitoneal telemetry probe implantation. We identified the Action Units (AUs) <i>orbital tightening</i>, <i>nose bulging</i>, <i>cheek bulging</i>, <i>ear changes</i> and <i>whisker retraction</i> as potential indicators of pain in ferrets. To evaluate whether these AUs could reliably be used to identify photographs taken before and after surgery, the photographs were scored 0, 1 or 2 (not, moderately or obviously present) by 11 observers that were blinded to the treatment and timing of the photographs. All AU-scores assigned to the photographs taken five hours after surgery were significantly higher compared to their time-matched baseline scores. Further analysis using the weights that were obtained using a Linear Discriminant Analysis revealed that scoring <i>orbital tightening</i> alone was sufficient to make this distinction with high sensitivity, specificity and accuracy. Including weighted scores for <i>nose bulging</i>, <i>cheek bulging</i> and <i>ear change</i> did not change this. As these AUs had more missing values than <i>orbital tightening</i>, their descriptions should be re-evaluated. Including <i>whisker retraction</i>, which had a negative weight, resulted in lower accuracy and should therefore in its current form be left out of the FGS. Overall, the results of this study suggest that the FGS and the AU <i>orbital tightening</i> in particular could be useful in a multifactorial pain assessment protocol for ferrets. However, before applying the FGS in practice, it should be further validated by incorporating more time points before and after applying (different) painful stimuli, and different levels of analgesia.</p></div

Ferret facial anatomy.

<p>Skin and superficial muscles were removed during dissection, drawing made by R. van Deijk.</p

Timeline of the study.

<p>The photographs were taken at the time points in boxes. The black and white boxes are time-matched (T_B2 was used as a baseline for T₂ and T_P2, while T_B5 was used as a baseline for T₅ and T_P5).</p

The ferret grimace scale.

<p>Photographs visualizing the normal appearance and changes (0 = not present, 1 = moderately present, 2 = obviously present) of the five Action Units that are used in the Ferret Grimace Scale.</p

Name, origin, insertion and action of the facial muscles of the ferret [30].

<p>Name, origin, insertion and action of the facial muscles of the ferret [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0187986#pone.0187986.ref030" target="_blank">30</a>].</p

Number and percentage of pictures (<i>N</i> = 209) that were scored ‘I not to know’ for <i>orbital tightening</i>, <i>nose bulging</i>, <i>cheek bulging</i>, <i>ear changes</i>, <i>whisker retraction</i> and overall pain pre- and post-training by 11 observers of 19 ferret faces at different time points (T_B2, T_B5, T₂, T₅, T_P2 and T_P5).

<p>Number and percentage of pictures (<i>N</i> = 209) that were scored ‘I not to know’ for <i>orbital tightening</i>, <i>nose bulging</i>, <i>cheek bulging</i>, <i>ear changes</i>, <i>whisker retraction</i> and overall pain pre- and post-training by 11 observers of 19 ferret faces at different time points (T_B2, T_B5, T₂, T₅, T_P2 and T_P5).</p