The taste preferences of dogs are a big deal to pet food manufacturers. After all, a food may contain quality ingredients and be highly nutritious, but it cannot benefit dogs if they refuse to eat it.
Traditional Palatability Tests
All pet food companies are concerned with their food’s tastiness (aka palatability) and they all measure this regularly. Traditionally, two standardized tests have been used. Both of these use groups of dogs (usually kenneled dogs) and collect data for 5 or more days:
- Single-bowl method: One bowl is presented to the dog and the amount of food that the dog consumes is measured. A food is fed for five days or longer, after which a new food may be introduced. The single-bowl test assesses overall acceptability of a food and also best mimics an in-home feeding situation (i.e. one food offered). However, a limitation is that it does not directly compare foods and so cannot reflect preferences or allow palatability ranking.
- Two-bowl method: In this test, the dog is presented with two bowls that contain different foods. The speed at which the dog approaches each bowl and the quantity of food that is consumed are measured. This test, called a forced choice procedure, is presumed to measure both palatability and preference. However, a limitation is that only two products can be compared.
Although these two tests have been the industry standard for many years, their limitations have led nutrition researchers to examine new approaches to measuring dogs’ food preferences. One of these, called “preference ranking” takes the novel approach of using food delivery toys to assess multiple products or ingredients, simultaneously.
PREFERENCE RANKING WITH FOOD DELIVERY TOYS
Two recent papers have studied the practical value and reliability of this type of test. The first is a validation study, conducted to find out if dogs readily engage in the test and to determine if test results are reproducible over time (1). The second used the food toy test to compare dogs’ preferences for five different meat protein sources (2).
How the Test Works
Many dog owners use food-delivery toys with their dogs. There are a wide variety of these products available, in a range of sizes, materials, and the methods they use to deliver food. Dogs enjoy these toys not only for the tasty treats that they deliver, but also because food-delivery toys provide environmental and mental stimulation (i.e. they are fun!). In this case, the researchers who developed the new palatability test chose to use the original Kong toy.
Teaching Phase: In the validation experiments, a group of 12 healthy, adult beagles were taught to anticipate different treats in different toys. This was conducted using a series of training sessions during which dogs were allowed to sniff each toy for several seconds. The toys were then placed, in a random order, approximately 2 meters away. Almost all of the dogs quickly learned that each toy contained a different type of treat. Interestingly, each dog developed his or her specific approach to extracting the tasty treats. (Anyone who has used food delivery toys knows how this goes….). They used various combinations of throwing, rolling, licking, and chewing to extract the food. Personally, I bet this part of the test was a whole lot of fun for both the researchers and the dogs.
Testing Phase: During the testing phases, the dogs were presented with toys containing baked treats comprised of either five types of fat ingredient (fish oil, butter, chicken fat, vegetable shortening, or lard); five different protein ingredients (chicken liver, fish, chicken, beef, or tofu); five starches (potato, wheat, corn, tapioca, or chickpea); or five combinations, backed into a food treat. All dogs were tested on all five sets of choices. Data collected included the order of selection and the time taken to extract each type of treat from the toy. The validation test was conducted by repeating this series of tests, with the same dogs and offerings, 12 months after the initial set of tests.
Validation Test Results
The dogs showed some strong preferences and these generally remained consistent over time:
- Fats: Dogs liked fish oil best and lard the least, with chicken fat landing somewhere in the center. (Who knew?)
- Proteins: In the protein ingredient phase, chicken liver was a clear winner. Least liked? Tofu. (Sorry vegetarians). Chicken, again, scored right smack in the middle.
- Carbs: Taters ruled here. Potato starch was a clear winner over all of the four other choices. Least popular? Chick peas.
- Food treats: The treat that was composed of fish oil, liver, and potato flour was a clear winner over the other four types of treat. The big loser was the treat containing tofu, lard, and chickpea flour.
One year later: The validation tests, conducted 12 months later, showed no statistically significant differences in these rankings. This provided strong evidence for the reliability and reproducibility of the new test.
Meat Protein Study Results
In this study, 12 dogs were tested using the same preference ranking procedures described above. Preference for five types of meat, cut into small cubes, was tested. The meats were beef, chicken, lamb, pork, and turkey. In addition, a panel of trained, human “sniffers” analyzed the aroma components of the five meats. Here is what the dogs (and the humans) related to the researchers:
- Beef it up: All five of the meats scored around mid-range on the 5-point scale. However, beef scored significantly better (i.e. more preferred) compared with chicken and pork.
- No pork, please: Pork was least preferred of the five meats, while turkey and lamb fell in the middle of the preference ranking.
- Complexity rules: Aroma analysis showed that beef had the most complex and the most intensely “meaty” aroma of the five types of meat. Dogs’ meat preferences correlated positively with the “meaty” and “roasted” aromas reported in beef.
Up on My Box: The box is out, but this time it is for a rave, rather than for a rant. (Fancy that!) I love this new test, for several reasons. First, from a science perspective, it changes the game plan from a forced choice test in which the dog must choose between two possibilities to a more flexible test in which, in its current iteration, the dog is given a choice of five products. The increased number of choices, plus the ability to observe and record the dog’s behavior while engaging with the toys, provide for a much more nuanced type of preference testing. In addition, because small amounts of test foods are used, this test lends itself to comparing preferences of individual food ingredients, something that has rarely been studied.
Second, this test has a lot to offer in terms of animal welfare and enrichment. Most of the dogs who are enlisted for palatability tests continue to be kenneled dogs. Offering opportunities for training with a human handler, for the mental and physical stimulation of manipulating and playing with a food toy, and the freedom to choose and interact independently are all enrichment approaches that can be beneficial to the quality of life of kenneled dogs. Bravo, bravo to the creators of this test!
Last, if you follow The Science Dog, you know that I frequently advocate for using in-home studies with dogs and their owners. Many canine cognition research labs have been doing these types of studies (brilliantly) for years. Nutritionists have been a bit slow getting on the bus, but there is some movement in this direction (see “Scoopin’ for Science“). This new preference test is a great fit for in-home studies. Consider that many owners, trainers and other pet professionals regularly train their dogs to use and enjoy food-delivery toys. Also consider that many trainers, myself included, are highly interested in not only our dogs enjoyment of their food, but also in how they rank various types of treats. Offering high vs. low level treats as positive reinforcers is an approach that many of us employ regularly in our training programs (treat ranking has also been studied; see “Treat Please” and “Speaking of Treats“).
Let’s hope that one of the next studies that we see with this new preference test involves dogs living in homes with their owners, doing their own little bit for science by playing with their food toys!
In the meantime, give it a try with your dog!
Here are the Steps:
- Select a set of identical food-delivery toys (3 to 6 toys, depending upon your dog’s interest and your pocketbook). These should be toys that your dog loves to engage with and that are relatively easy to extract food from (otherwise, you may be here a while).
- Choose a set of treats or foods that you would like to your dog to rank in terms of preference. Place each type in a separate toy (you can mark the toys to identify them and keep treat identification straight).
- Use a quiet area of your home or a place that you regularly use for training. Minimize distractions as much as possible. Test when you know that your dog is hungry (for Labs and Goldens, this is any time at all).
- Ask your dog to sit. Present him with each stuffed toy, allowing him several seconds to sniff. (Once your dog understands this new game, you may not need this step). Leaving him in a sit-stay, walk ~ 8 feet away and place all of the toys in a line.
- Release your dog and observe: (1) his level of interest in each toy; (2) the order in which he starts to extract food from the toys; (3) the time to extract food from each toy.
- Repeat daily with the same treats, presenting them in random order. It is important that your dog learns to expect different treats in each toy (this may take several repetitions of the test – be patient!).
- Replications are important in science, even with an “n of 1”. Over several reps, you should begin to see your dog’s preferences emerge. Use this information in your training program and when using food-delivery treats as enrichment toys with your dog!
- Li H, Wyant R, Aldrich G, Koppel K. Preference ranking procedure: Method validation with dogs. Animals 2020; 10, 710:doi:10.3390/ani100440710.
- Tsai W, Goods E, Koppel S, Aldrich G, Koppel K. Ranking of dog preference for various cooked meats. Poster presentation; Society of Sensory Professionals annual meeting 2018; https://www.sensorysociety.org/meetings/2018Presentations/38_Tsai.pdf