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