Figure 1. In this example of the apparatus used in a typical test, a tray in the response area contains food wells with objects covering them. The dog displaces one of the objects with its nose. The correct object conceals a food reward.
In the companion animal field, palatability assessment is
critical for developing foods, treats and medications that pets
will willingly consume. Because animals can't declare their
preferences, we must use other means to find out what foods
they like. Ultimately, any method must enable us to objectively
rank an animal's preference between two (or more) foods. CanCog
Technologies has developed an alternative approach, the
cognitive palatability assessment protocol (CPAP).
Advantages over standard two-pan tests
The standard two-pan method of assessing food preference in
pets compares how much of two foods are eaten in a specific
amount of time. The test offers several advantages: It
generally agrees with owners' reported opinion of their pets'
enjoyment of a food, it is low in cost and can be done quickly
in terms of data acquisition.
The two-pan test also has inherent limitations. First, the
data show significant variability, particularly within
individuals. Second, the test has difficulty detecting subtle
differences in formulation. Third, the two-pan test doesn't
afford control for how different foods may affect the
palatability of each other, or demonstrate the long-term
effects of caloric intake and nutritional value.
Instead of relying on quantity consumed, CPAP helps the
animal indicate which food it prefers without actually eating
the food. CanCog uses a unique cognitive procedure based on
associative learning that is similar to how consumers select
food at a supermarket, i.e., based on packaging.
Cognitive testing procedure in dogs
We have examined cognition in dogs for several years with an
emphasis on age-related cognitive changes (Adams, et al.,
2000). An example of the testing apparatus we use is shown in
Figure 1. In a typical test, the dog enters the apparatus and a
technician slides a tray into the response area. The tray
contains food wells with objects covering the wells. As with
most of our tests, there is only one correct choice. If the dog
selects the correct object, it finds a food reward in the well
One of our tasks, an object-discrimination learning task,
can be solved by using an associative learning strategy. One of
two objects is always placed above the food reward. The dog
simply has to learn the association between a particular object
and the presence of a reward. Once that happens, we reverse the
reward-object association. We have found during this reversal
test, aged dogs have impaired responses compared to young dogs
(Tapp, et al., 2003).
We use a similar procedure to examine palatability, but in
these tests there are two objects that could be correct. Each
of the two objects is associated with a different food. To
ensure the animals have actually used associative learning, we
include a third object that has no reward associated with
Initial CPAP development
In the initial development of the task, we used a four-phase
procedure to compare palatability of a moist food with dry
kibble (Araujo and Milgram, 2004). The first phase determined a
preferred object out of three. In the subsequent phase, we
presented a single, nonpreferred object in association with one
of the test foods.
The third phase was used to assess palatability. The dog was
presented with three objects, one of which (its originally
preferred object) was not associated with any food. Initially,
dogs picked their preferred object, but they rapidly learned to
avoid it, and with repeated testing every one of the dogs
selected the object associated with the wet food (see Figure
2). In the fourth phase, we switched the food-object
associations, so the preferred food was now under a new object.
The animals accordingly switched their choices to the new
object associated with the wet food.
Comparison with the two-pan test
To further validate the CPAP, we compared two foods that
were identical in composition, except for the protein source
(one was chicken and one was lamb; Araujo, et al., 2004). Based
on previous work, we expected the two to be similar in
palatability, but that was not the case.
We used six Beagles and found that they all showed a strong
preference for the chicken-based food. We then used the same
six dogs and an additional seven dogs that were naïve to the
diet. We found a similar, but smaller, preference using the
two-pan test over the CPAP, but this was mainly driven by the
dogs with experience. The dogs that were naïve to the two foods
showed no difference in preference.
To compare stability of the two tests, we looked at
preference over several days and also following feeding of
various diets. Dogs showed the same preference on the CPAP for
the entire test period. By contrast, preference according to
the two-pan test was highly variableeven in dogs that had
previous experience with the food. Similarly, feeding prior to
two-pan testing resulted in reduced food consumption during
testing, and reduced the ability to detect a difference. No
difference in the ability to detect a preference was noted in
the CPAP under identical conditions.
Conflict with a satiety-suppressing
In a final test of the CPAP protocol, we examined the
palatability of a specially formulated, appetite-suppressing
food. The food was effective, in so far as animals would eat
very little, but it also convincingly failed the two-pan test.
Was this because the food suppressed appetite, or because of
decreased palatability? When we used the standard two-pan test
to compare the food with another, the appetite-suppressant diet
lost, but again there was considerable variability.
The CPAP procedure, however, told another story; several of
the animals showed a consistent preference for the
appetite-suppressing food over the standard. There was
substantial group variability, but much less individual
variability, which is what we would expect if the foods were
similar in palatability.
Future directions for CPAP
Like people, dogs can show their preference based on
packaging, as demonstrated by the CPAP protocol in which they
select an object rather than a food. Food preferences
established by CPAP are robust, stable and not influenced by
confounding effects of other foods, including those intended to
reduce food consumption. The disadvantage of CPAP is that it
requires more time than the standard two-pan test and, thus, is
Because the CPAP requires only small quantities of food and
is a robust test, it may be the best for preference assessment
of slight changes in food formulations, pharmaceutical
formulations and treats. With the industry pushing toward
improved health, while still providing highly palatable foods,
CPAP may be considered a compelling adjunct to standard
Advantages Reduced individual variability; Increased
ability to detect subtle formulation differences; Doesn't
rely on consumption of food; Food preferences established
are robust, stable and are not influenced by confounding
effects of other foodsincluding those intended to reduce
food consumption.Disadvantages Requires more time than the
standard two-pan test and, in this sense, is more
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