Preference and Motivation Testing as They Relate to Animal Welfare

1. Preference and Motivation Testing as They Relate to Animal Welfare Camie Heleski

2. Seems like the ideal way to let the animal “tell” us which management scenario they prefer • But, does the animal truly choose the option that maximizes long term fitness • (e.g. does child given choice of balanced meal vs. candy bar make the “good” choice?)

3. Preference tests • tests that require animals to choose between two or more different options or environments • e.g. hens given options of different types of cages • hens given option of dust bath or no dust bath • horses given option of treadmill exercise or stall

4. Preference tests • Used since early 1970’s (though anecdotally much longer than that) • Have been used to establish animal preferences for: housing options (temperature, illumination, preferred bedding), loading ramps, nest boxes, etc.

5. Motivation tests • How hard will an animal work to gain access to its preferred option • How hard will an animal work to avoid its less favored option

6. Animals’ preferences may vary with time of day, age & experience of animal • Tests sometimes confuse familiarity with preference • Animals may not be capable of distinguishing short term benefits of small magnitude from long term benefits of large magnitude

7. To use preference testing to answer questions about animal welfare... • 1. We must ensure that experiments adequately reflect the animals’ preferences • 2. We must establish how strongly motivated the animal is • 3. We must consider that preferences will not always correlate with enhanced welfare.

8. Fundamental to the premise of using preference testing to evaluate animal welfare is the assumption that animals make choices that are in their best interests.

9. Brambell Committee, 1965 • First proposed “asking” the animals’ opinions about their environmental preferences • 1973 - hens and flooring options • offered various pairwise choices • slightly preferred traditional chicken wire

10. Problem of familiarity • Dawkins (1977, 1980, 1981) reported that hens that had lived in battery cages, on the first day given a choice between the cage and a grassy, outdoor run chose the battery cage; (thereafter the trend was strongly reversed)

11. Other preference studies... • Pigs prefer substrate to root in. • Hens prefer access to a dust bath. • Mink like a swimming bath. • Recent work - ISAE, 2000 (Tucker et al.) • Dairy cattle preference tested on bedding choices chose sawdust more than sand or “cow mattresses”

12. Using preference testing to evaluate horses’ housing preference

13. Our weanling horse study showed preference for being by penmates vs. being by self • showed they would work hard to engage in grazing • I would have liked to preference test whether they preferred the paddock or the stall and how hard they would work for preference

14. Asking suitably complex questions... • Some initial pig work on whether or not they prefer pens w/ straw bedding gave inconsistent results • prefer or avoid depending on environmental temperature • strong increase in preference for straw, pre-parturition (Steiger et al., 1979, Fraser, 1985)

15. Ongoing research on horses looking at the “need” to exercise • horse given a Y maze choice as to whether to go back to its stall or go onto a treadmill and trot • they concluded that horses do not “need” to exercise…do we agree with conclusion?

16. Assessing the strength of animals’ preferences • Just because a preference is shown does not necessarily mean an animal’s welfare is unfairly diminished when it does not have access to that choice • e.g. horses prefer corn to oats and alfalfa to brome grass - does that mean the horse has poor welfare if fed oats and brome grass? (not if the oats and brome meet its nutritional needs)

17. Dawkins (1983) studied hens’ motivation to dust bathe • compared dust bathing to desire for food after 0, 3 or 12 hours of food deprivation • at 0 hours, they had stronger motivation to dust bathe • at 3 hours, the motivation was about = • at 12 hrs, food motivation was greater

18. This type of testing has given rise to using economic principles to evaluate motivation toward preferences • Commodities for which a given percentage increase in price results in a decrease in the quantity demanded are said to have elastic demand and are sometimes called luxuries; • those for which a given percentage increase in price results in little change in the quantity demanded are said to have inelastic demand and may be called necessities

19. Matthews and Ladewig (1994) used these concepts to evaluate pigs’ needs for food or social contact • pigs had to perform an operant response (pressing a nose plate) to receive food or social contact • as they had to press an increasing number of times, they would still do this for food, but did it less for social contact

20. Can use similar philosophy to evaluate what an animal will work to avoid (aversion testing) • Rushen (1986) tested sheep that were sheared with electroimmobilization and sheep sheared without electroimmobilization • and determined sheep learned to avoid the former option

21. Conclusion • How do preferences impact welfare… • if preferences have the backing of strong motivation, one must assume that the animal “suffers” to some degree when it cannot perform that behavior (e.g. horses and grazing) • but if biological functioning is not impacted and, perhaps, animal develops compensatory behavior (e.g. sham grazing) - is the animal’s welfare impacted? • I believe, yes, but this is not a universally held belief