preference and motivation testing as they relate to animal welfare camie heleski
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Preference and Motivation Preference and Motivation Testing as They Relate to Testing as They Relate to
Animal WelfareAnimal WelfareCamie Heleski
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?)
Preference testsPreference 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
Preference testsPreference 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.
Motivation testsMotivation 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
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
To use preference testing to To use preference testing to answer questions about animal answer questions about animal
welfare...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.
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.
Brambell Committee, 1965Brambell 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
Problem of familiarityProblem 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)
Other preference studies...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”
Using preference testing to evaluate Using preference testing to evaluate horses’ housing preferencehorses’ housing preference
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
Asking suitably complex Asking suitably complex questions...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)
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?
Assessing the strength of Assessing the strength of animals’ preferencesanimals’ 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)
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
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
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
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
ConclusionConclusionHow 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