I was at the gym recently, swimming laps. After my work-out, I was sitting by the side of the pool and a fellow swimmer and friend stopped to chat about dogs. He has never owned a dog, but his daughter has been pressuring him and he thinks she is finally old enough to take on the responsibility of caring for a dog (good dad!). So, I was anticipating a discussion about breeds, where to look, training, feeding, etc. That is not where this was going at all. Instead, he wanted to talk about poop:
Me: “So, does she have a breed or breed-type that she is considering?”
Him: “No…..not yet. What I really want to ask you about is……the poop thing.”
Me: “Um…..what?”
Him: “You know. I see all of the people in our neighborhood taking their dogs for a walk in the morning and they all carry these bags with them and then, ugh…..they all PICK UP THE POOP WITH THEIR HANDS!!!!”
Me: “Well, not exactly; there is a plastic baggie involved. But regardless, what is your point?”
Him: “I just find that so gross and disgusting. I don’t think I could do it.”
Me: “Wh…What???”
Him: “Ick. Yuck.” (Accompanied by a squeamish expression that I have never seen on the face of a grown man).
Me; “Okay, let me get this straight. You are a triathlete. You regularly beat the crap out of your body by swimming, running and cycling ridiculously long distances. You have backpacked and camped all over the country, with no “facilities’ and sometimes not bathing for days……and you squirm at picking up dog poop in a plastic baggie?”
Him: “Yeah, that about covers it.”
Me (laughing): “You gotta get over that dude. Take a class or something. All dog folks pick up poop. It’s no big deal.”
Him: “Hmmm…..” (not buying it).
It really is no big deal. Many dog owners are not only comfortable with poop scooping, we also regularly examine the quality of our dog’s leavings as a general barometer of their health and the quality of the food that we are feeding.
So, when I learned of a recent study that asked a group of dog owners to do some “poop scoopin’ for science” I was only surprised that there have not been more studies of this nature published in the past.
The Issue: Those of you who have read Dog Food Logic know that I personally advocate for increased transparency in the pet food industry and for the need to provide dog owners with information that is actually useful to us when selecting foods. Without question, one of the most important measures of a food’s quality is its digestibility – the proportion of the food that a dog’s gastrointestinal tract is able to actually break down (digest) and absorb into the body for use. Digestibility correlates well with both ingredient quality and proper food processing techniques, so this information would be very helpful for dog owners to have. However, the vast majority of companies do not provide it. The only (very rough) estimate of food digestibility that we have is that gleaned by regularly examining the quality and quantity of our dog’s feces. A behavior that, in addition to providing very little real information, lends itself to weird looks from neighbors such as my swimming friend. A crappy state of affairs, indeed.
Industry’s Position: When challenged, representatives of the pet food industry generally deflect criticism by maintaining that current AAFCO regulations do not require reporting of food digestibility. (The old “we don’t gotta so we ain’t gonna” defense). Further, not all pet food companies regularly measure digestibility because doing so requires them to conduct feeding trials with dogs which in turn requires access to research kennels and laboratories. Such studies are expensive and may be cost prohibitive for some of the smaller companies that do not maintain their own kennels or in-house analytical laboratories.
Fair enough. However, what about using dogs who live in homes? Why not enlist everyday Citizen Scientists who are dedicated to their dogs, feed commercial dog food, are concerned about quality, and who do not squirm at picking up dog poop? Not only would this lead to increased numbers of dogs enrolled in these trials (thus supporting improved accuracy of digestibility estimates), it would also allow needed comparisons among breeds, ages, life styles and activity levels of dogs, and could get information about food quality out to the consumers who need it. Another definite advantage of in-home studies is that they lead to reduced need for kenneled research dogs, a clear animal welfare benefit.
Happily for us, a group of researchers from two universities in The Netherlands were thinking the same thing (1).
The Study: The objective of their study was to develop a simple method of measuring dog food digestibility that could be used with privately owned dogs living in homes. They recruited a group of 40 adult, healthy dogs and asked their owners to feed a test food (and nothing else) for a period of 7 days. Amounts to feed each dog were pre-measured and the volume the dog consumed each day was recorded. In this study, the test diet was a commercial dry (extruded) food formulated for adult dogs. After seven days of feeding, the owners were asked to collect all of their dog’s feces for a period of 24-hours. The feces were frozen and submitted to the researchers for analysis.
Here is a flow-chart showing how a digestibility trial works. It is conducted in the same manner with kenneled dogs, although feeding and feces collection periods can vary:
Results: The owners recorded the amount of food that their dog consumed each day and collected all of their dog’s feces over the final 24-hours of the study. The researchers then analyzed the nutrient content in the food that was consumed and in the feces that were excreted. From these data, they calculated the proportion of the food that each dog digested, called a “digestibility coefficient” and average values for the entire sample of dogs. In this experiment, the food’s dry matter digestibility was 77.4 % and its protein digestibility was 77.7 %, values that reflect a food of “low to moderate” quality. The variability between dogs (as reflected by the standard errors), was found to be low. This suggests that the dogs in the trial showed consistency in their ability to digest the food and supports the in-home trial as a valid procedure. In addition, the study reported compliance in 39 out of 40 homes, demonstrating some pretty dedicated poop scooping.
Up on the ol’ Box: Another recent study evaluated a set of eight commercial dog foods using both nutrient analysis and a set of feeding trials like the one above, but with kenneled dogs (2). They found a very wide range in the overall (dry matter) digestibilities and protein digestibilities among the eight products and noted that these differences would not be reflected by information that was provided on the pet food labels. The authors went even further, stating: “…we have to note that there is no comprehensive list of information available to the consumer to evaluate the quality of commercial diets. A combination of laboratory analyses and estimation of digestibility coefficients is the only way to perform an accurate and complete evaluation of the quality of a commercial diet” And yet, not all pet food companies supply complete nutrient levels for their foods and no pet food companies regularly provides digestibility coefficients to dog owners.
The results of this pilot study tell us that in-home studies with owned dogs can provide needed information about dog food quality and can allow the study of factors that may influence how well dogs utilize different foods, such as age, breed, size, health status and activity levels. Compliance was very good; these owners were willing to do their part, scooping poop for science. Now all that we need is for pet food companies to step up and begin to conduct in-home studies and make the information that they provide available to the dog folks who care.
Cited Studies:
- Hagen-Plantinga EA, Bosch G, Hendriks WH. Practical approach to determine apparent digestibility of canine diets. Journal of Nutritional Science 2014;3;e31:1-4.
- Daumas C, Paragon BM, Thorin C, Martin L, Dumon H, Ninet S, Nguyen P. Evaluation of eight commercial dog diets. Journal of Nutritional Science 2014;3;e63:1-5.
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E
The Science Dog 
Is digestibility necessarily good?
Doctors encourage us humans to eat less refined food and more roughage. Fiber is said to have many virtues . . . but digestibility isn’t one of them.
I’d guess that the undigestible components of dog food are mostly cellulose/hemicellulose, bone from animal byproduct meals, and a bit of lignin (correct?). Is there any evidence that those are bad, other than giving us a bit more to pick up in our doggy bags . . . and yielding fewer kJoules/kg of food?
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Hi Jen – Great question. When we are encouraged to consume more “roughage”, as you know, this refers to fiber, which has numerous benefits to gastrointestinal and overall health. This is also true for dogs, who benefit from moderate amounts of several types of fiber in their diets. And yes, increasing certain types of dietary fiber in the diet does decrease DM digestibility, but only when the amount that is added is excessive. However, normal (and needed) levels of fiber do not reduce a dog food’s digestibility (and as with humans, are beneficial). With commercial and even some homemade dog foods, a major factor in overall digestibility is the quality of the protein source that is used. (There is also a lot of evidence that a food’s digestibility correlates very strongly with the percent of fat in the diet, but this does not negate the fact that a poor protein source will negatively affect diet digestibility). So, when we use digestibility coefficients as a “marker” of quality in commercial foods, we are generally using it to give us a rough estimate of protein quality along with overall nutrient availability. Again, if the food was really high in crude fiber, as we see in some weight loss foods, you would see reduced digestibility, and this is a bad thing not a good thing, as too much fiber can inhibit the availability of other essential nutrients. Thanks for posting and for your thoughtful points!
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p.s. forgot to say, as usual, interesting article. Thanks for posting.
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Very good insight. Canine nutrition can be so confusing, and it’s refreshing to hear about something other than “make sure meat is the first ingredient.” It’s also nice to know that another country is embracing at home trials (kudos to Duke’s Canine Cognition Center here for also reaching out to pet owners, but sadly, that is still an anomaly). Science is so bent on having control over everything so data is accurate and not skewed by outside variables, but quite frankly, the clinical environment itself may skew results in some instances. Do dogs behave the same in a lab or test kennel as they would on average? Probably not in every circumstance. I like the idea of averages, so that data can be considered valid based on trend. Hopefully companies in this country will take notice of what’s going on abroad and consider more liberal research options.
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I would agree that dogs do not necessarily behave the same in a lab or test kennel. Even in an adoption pen, they are not necessarily “themselves”. They are thinking creatures capable of rationalizing their circumstances and coping as best they can. Many dogs in adoption areas need anxiety meds to stabilize them and prevent them from losing control and hurting themselves (GSD’s!). Many a chewed tail has been a result of limited/unusual circumstances. While many dogs will no doubt perform in a predictable manner, there are many that would not. As an aside, I have to only contemplate an imminent uncontrollable event and my body stops performing “normal”!
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Hi “Wags” – Excellent points. There is no doubt that even though a number of “life variables” are controlled in a kennel setting, it is those very variables that are important to study in terms of how they affect dogs’ nutrient needs and ability to utilize foods. The really neat thing is that researchers are really beginning to recognize the benefits of tapping into dog folks’ willingness to help them to learn more – the cognition labs around the world, as you mention, are one of the best examples of this! We can hope that nutritionists will follow suit as studies like this gain acceptance. Thanks for posting and for reading! Linda
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I live out near the Chesapeake Bay and many of our communities out here have very poor waste water retention abilities, so a lot of our surface water, goes right into the bay. In my county, we’re looking at the effects of unscooped poop and it’s effects on the bay. Digestibility coefficients can help greatly (if we can get consumers to understand it and go along with it) in the reduction in the amount of fecal matter (including bacteria, viruses, and parasites) going into the bay and destroying our aquatic life. Kudos for the info!
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Hi Eric, Good to hear from you, old friend! (Well, I am old-ish; you are still a spring chicken, of course! 🙂 ).You make a very interesting point. However, isn’t one of the biggest causes of pollution to the Chesapeake caused by the waste from intensive chicken and dairy farms and from the overuse of agricultural fertilizer? I have to wonder if unscooped dog poop is a proverbial drop in the poop bucket, by comparison to those sources. (Does elderly Mrs. Smith not picking up after her toy poodle come close in volume to a chicken farm housing 20,000 animals?). Just wondering…… Regardless, as you mention, anything that helps to encourage folks to be more responsible dog owners is a good thing. Hope all is well with you and yours.
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Good article but to go back to your chat with Mr. Yukky…. Poop! I get concerned whenever I hear an adult contemplating getting a dog for their child. Who is REALLY going to be looking after it? Have they considered the life span of the dog vs the time the child is likely to be still at home? Have they considered who is going to take on the responsibility of the dog at that time. Our local shelter is often the recipient of dogs from such circumstances. Very sad.
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Colin, If that person has a problem picking up dog poop and it is his daughters first dog, maybe they should try another type of pet first. Also, I was once told to take a half full glass of water and add some dog food to it then let it sit, then come back later to see how it dissolved and this would show me how the food would likely digest in my dogs stomach. I did this and I was amazed at how the dog food ballooned up like a sponge. I changed to a dog food that was suggested at the time and did the test again and the new food broke down considerably. Sorry I cant remember the dog foods tested because it was years ago. Thanks for the good read.
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Hi Allen, Placing dog food into a glass of water may show you how soluble the food is (in water), but will not provide an estimate of its digestibility when exposed to a dog’s gastric secretions and digestive enzymes. (Sorry, if something seems too easy to be true, it usually is…. 🙂 ). The expansion that you saw, on the other hand, does give a rough estimate of the proportion of starch in an extruded food, as these are the ingredients that expand the most in water. (An extruded food that is high in protein/fat and low in starches will expand less by comparison). However, this difference does not correlate with digestibility. To know that, you need a feeding trial. Thanks for the comment and for reading! Linda
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I don’t mean to be troublesome, but my brain won’t stop mulling this over. It seems to me that dog food might not be digestible for different reasons, and that one’s conclusions about digestibility could vary quite a bit depending on whether you work on a dry weight, volume, or caloric basis.
Example: Some foods seem to have quite a bit of ground bone in them . . . and hence come out with high ash content. There was a period where I feed my dogs a lot of chicken carcasses. Their poop was dense, hard, and sort of cement-like. The volume was pretty low, but the density was high and I’d guess the water content was also low . . . so on a dry weight basis, I’d guess the indigestible fraction would come out pretty high . . .both for feeding chicken carcass and for a bone-rich kibble.
Example: fatty foods. If I understand correctly, dogs digest many sorts of fat very efficiently. On a dry weight basis, fat has a bit more than twice the caloric content of carbs; it’s also more energy-rich than protein. So if you measure digestibility in energy terms, you can up the measure by upping the fat. This may not be healthy for dogs that tend to pack it on.
Example: the lignocellulosic fraction. I know a lot more about grazer metabolism than carnivore/omnivore metabolism. The livestock industry has done a lot of measurements of what goes in, what goes out, and how efficiently the input builds muscle mass (or contaminates groundwater). Cow poop is mostly lignocellulose. It makes for bulky poop, with reasonably high caloric values per kg dry weight (hence the use of cow pats as fuel in some agrarian societies). Dog foods that include bran are likely to have more lignocellulose.
Example, starch . . . I’d guess the more complex and perhaps less digestible forms might be better for health. Or is processed carbohydrate better? Dunno. My guys love carrots (most of the calories are in the starch). Their poop is full of orange bits after they have eaten a carrot or two. I don’t think their systems do a good job of breaking down the cell wall material and thus not much is digested. Is this good or bad? Dunno.
In sum: high digestibility from high fat, low ‘ash’ and low fiber may be quite different from high digestibility from high protein from some meat-based meal. Low digestibility that reflects a lot of ground bone may be different from that which comes from excess fiber. Fiber in fresh fruit and veg may be different from fiber added to the dry stuff put into kibble.
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Hi Jen – Yes, all that that you say is true. As I said in my first response “So, when we use digestibility coefficients as a “marker” of quality in commercial foods, we are generally using it to give us a rough estimate of protein quality along with overall nutrient availability” (Notice – and overall nutrient availability). Your point about ash emphasizes why it is important to look at organic matter digestibility vs. DM digestibility (this will give you an estimate of the impact that the food’s mineral [ash] content is having on digestibility). In addition, protein digestibility, and fat digestibility can also be calculated from a feeding trial. I simply emphasized protein in the essay because the type of protein meals that are used in dry extruded foods are an important factor in determining total (DM) digestibility. Linda
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I had to laugh about Mr. Yukky’s evident and misplaced squeamishness. As an avid equestrian of over 50 years I found that my (high profile professional )husband’s circle of friends included many persons best described as “ladies who lunch.” The most frequent question I got from these women was not, as one might expect, “what kind of horses” or “do you compete” but instead went like this: “Ewwwww, what do you do with all the horse POOP!” These same women could also be counted upon to snicker and elbow each other during parades where the animal entries, of whatever, description, were followed by the cleanup crew entries. Whether my dogs or my horses the first strong indication of health – or otherwise – is that deposit of recycled food stuffs, ranging from suddenly and dramatically nonexistent (in horses, impaction colic is suspected) to raspberry puddles (hemorrhagic gastroenteritis, as suffered by one of my JRTs). I am disappointed that more humans especially athletes like this Mr. Yukky seems to be, just don’t make the effort to understand the workings of mammal bodies and pay attention to those workings accordingly.
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