2 results
Gas killing of rats: the effect of supplemental oxygen on aversion to carbon dioxide
- RD Kirkden, L Niel, SA Stewart, DM Weary
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- Journal:
- Animal Welfare / Volume 17 / Issue 1 / February 2008
- Published online by Cambridge University Press:
- 11 January 2023, pp. 79-87
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High concentrations of carbon dioxide (CO2), used for killing laboratory rodents, are known to be more strongly aversive to rats than sweet food items are attractive. This study investigated whether the maintenance of a high oxygen (O2) concentration, using a gas mixture of 70% CO2 and 30% O2, would reduce aversion to CO2 during a gradual-fill procedure. Eight male Wistar rats, aged 10 months, were housed individually in an apparatus consisting of two cages, one higher than the other and joined by a tube. In a series of trials, subjects entered the lower cage for a reward of 20 sweet food items. The gas was turned on at the moment the rat started eating the reward items and flowed into the lower cage at a fixed rate. There were four treatments: 1) 100% CO2 at 14.5% cage volume min–1; 2) gas mixture at 14.5% min–1; 3) gas mixture at 21.0% min–1, which delivered CO2 at approximately 14.5% min–1 and 4) air, with each subject tested with each treatment four times. Measures of willingness to stay and eat in the lower cage (latency to stop eating, latency to leave and the number of reward items eaten) were much lower in all three gas treatments than in air, indicating that the CO2 and the CO2 + O2 mixture were both more strongly aversive than sweet food items were attractive. Comparing the gas mixture with 100% CO2, the latency to leave and the number of reward items eaten were slightly higher in the CO2 + O2 mixture at 21% min–1 than in CO2 at 14.5% min–1, indicating that the addition of O2 slightly reduced the aversiveness of CO2 in the gradual-fill procedure. This reduction is not enough to warrant recommending the use of CO2 + O2 mixtures for killing rats.
Motivation for group housing in gestating sows
- RD Kirkden, A Pajor
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- Journal:
- Animal Welfare / Volume 15 / Issue 2 / May 2006
- Published online by Cambridge University Press:
- 11 January 2023, pp. 119-130
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It has been argued that the welfare of gestating sows is higher in groups than singly in stalls, in part because group housing offers them more space and social contact. This study set out to ascertain how important access to a group pen was to dominant sows housed in stalls, using a measure of motivation. Subjects were trained to perform a panel-pressing task, then housed in a stall and permitted each day to work for a day's access to a fully slatted group pen containing two familiar, subordinate sows at a stocking density of 2.7m2 per pig. Social ranking was determined by observations at mixing and from feed competition tests. The fixed-ratio schedule was increased daily and the highest schedule reached (the reservation price) was used as a measure of motivational strength. To interpret this measure, it was compared with the highest schedule that subjects reached when working for access to the last 1/16th of their estimated ad libitum daily food intake after having consumed the first 15/16ths free. Sixteen subjects were tested, eight working for access to the group pen first and eight for access to the food first. Seven subjects yielded useable data: four reached a higher schedule working for food and three reached a higher schedule working for the group pen. Overall, subjects attached no more importance to a day's access to the group pen than to the last 1/16th of their estimated ad libitum food intake. It is likely that the subjects were close to satiation when working for food because consumption frequently fell substantially short of the ‘ad libitum‘ allowance. These results suggest that dominant, stall-housed sows are only weakly motivated to gain access to a fully slatted group pen, although motivation might be higher when deprived of access to the group pen for longer than one day, if tested at a different time of day or if the quality of the group space was improved; these three possibilities still need to be tested.