Carbohydrates 2: Dietary Fibers

Dietary fibers in my opinion are the most important carbohydrates to consider in diet formulations for animals, particularly for our pets.

Fiber often gets labeled as "filler" although some people refer to all carbohydrates in pet foods as fillers and that's just silly (especially to those of you reading this blog).  Now, if you are feeding a food like Ol Roy (don't tell me if you are!), yes, you are feeding way too carbohydrate and your dog (or cat) will have the fecal output to show for it.

First off, dietary fiber is not a single or simple group of compounds.  In fact, they are extremely complex and diverse carbohydrates with diverse physical and chemical properties.  Structurally, some fibers are soluble and some are insoluble.  Some are viscous and have very high water holding capacity, while others are non-viscous.  Some are fermentable in the bowel and others are not. Lastly, they can be combinations of the above.  So, you can have soluble - viscous - fermentable fibers for example (those are my favorites), or you can have something like psyllium (Metamucil), which is actually a very soluble-viscous-non fermentable fiber.

The frustrating issue for me is that the label and analytics involved, don't necessarily tell you about those properties.  If you look on a label of food (for you) at the grocery store, you will see that perhaps it breaks down the fiber into Soluble and Insoluble, but often gives you the Total Dietary Fiber (TDF) amount.  On an herbivore diet such as for cows or horses, the label will likely (hopefully) include ADF (acid-detergent fiber) and NDF (neutral-detergent fiber).  The values of TDF, ADF and NDF and obtained through totally different analyses in a lab.  On our petfoods, we will see a value called "Crude Fiber" which also is a totally different analysis for fiber.  Unfortunately, crude fiber is a completely worthless value to use.  The assay destroys all of the soluble fibers and many insoluble fibers and only recovers portions of cellulose, hemicellulose and lignin (totally insoluble, non viscous, non fermentable).  Therefore, a petfood might have a crude fiber value of 2.5% on the label but in reality, may have TDF values closer to 10% or even 20% depending on the ingredients used.

"Shadow"

Ideally, I want fibers on the ingredient list that will provide some soluble characteristics.  Soluble - viscous - fermentable fibers can alter gastric emptying and transit time (this can be good and bad), aid in management of pH along the G.I tract, provide volatile fatty acids for energy to the cells lining the gut, and aid in the management of blood lipids and glucose. These fibers can be very good in appropriate concentrations.  In addition, many of these fibers provide prebiotic properties and help maintain optimal microflora populations that provide a strong basis for overall health and immunity.

Many folks like to use canned pumpkin in diets.  Canned pumpkin contains about 30% TDF.  That fiber is about 20% soluble and 80% insoluble; therefore, it does provide a nice blend.   Due to the high TDF concentration and the blend of soluble to insoluble, pumpkin is an ingredient that I can use effectively across a huge range of species including dogs and cats, bears, elephants and primates.

My dog's raw diet does contain grain (and quite often pumpkin).  I use oats and barley predominately at 10% of the the diet (as-fed).  Oats and barley contain 30 and 12% TDF, respectively.  Corn and wheat actually contain about 19 and 17% TDF while rice contains less than 2% (white rice).  Barley has the highest percentage of soluble fiber, consisting of 30% of the total TDF.  This gives barely some very viscous qualities or thickening properties.  Oats on the other hand only have about 10% of the TDF as soluble; therefore, combined, I get a very nice blend of fiber qualities in my diet.  Corn, wheat and rice contain 18, 14, and 20% of the TDF as soluble.  Rice has such a low TDF value overall, I tend to not use it much, especially because it also has a very high glycemic index.  Corn and wheat are definitely options for those animals that tolerate them.  I will use fresh corn in my diet because an additional 15 - 20% (as fed) will consist of  fresh fruits, greens and vegetables.  If you are wondering, the breakdown looks like this:

55 - 60% muscle meat
10 - 15% organ meat (mostly liver and heart)
15 - 20% Greens, vegetables, fruit (seasonal)
10% grain
I supplement with eggshells for calcium and feed raw meaty bones 2-3 times week.

No doubt, fibers have personality!!! I love them!

Carbohydrates 1 = Sugars and Starches

Next to "grains", sugars and starches are likely the biggest culprits of "anti-carb" propaganda in relation to petfoods.

Sugars are typically referred to as mono and di-saccharides and common examples  include glucose, galactose, fructose, sucrose (table sugar), lactose (milk sugar), and maltose.  They are typically included in foods to increase palatability, change viscous properties, alter texture, and/or provide color (browning reactions).  Honey is an ingredient in many of my recipes, specifically because of its balanced concentration of gluocse and fructose.  It provides a sweet taste that many dogs appreciate (or at least my Keegan thinks it's awesome).  Interestingly, I often hear performance dog handlers indicate that honey makes their dogs sluggish.  I do believe this is similar to some of the dogs that collapse during exercise (specific genetic diseases excluded).  Fructose metabolism is a bit more complicated than glucose metabolism.  It will either get used for energy or converted directly to fat (this is why high fructose corn syrup is so "fattening" for us humans if we don't use it for energy).  Therefore, in our performance dogs, if they have a high glucose demand that gluconeogenesis is not maintaining, then yes, honey may not be the best option and more rapidly available carbohydrate sources are  optimal.

Keegan (Photo by: Marsha Kingsley)

Starches are interesting ingredients as well.  Starch in its basic definition is just a lot of glucose molecules joined together in one of two patterns, linear (amylose) or branched (amylopectin).  Amylopectin is more rapidly digested and thus, higher concentrations result in higher glycemic index.  Food sources vary in the ratio of these two forms; therefore, one type of grain or carb does not equal another...hence all the confusion.  For example, low amylose and high amylopectin in rice, make it rapidly digested but also give it a very high glycemic index.  It is often used as the "go to" for many diets because of its high digestibility. I tend to not use it so much because of its very high glycemic index.  Instead I use primarily barley and oats in my formulations, or when I'm looking at petfoods. I like the fact that both have nice amylose to amylopectin ratios and they each have additional cooling (barley) or heating (oats) properties (a topic for later discussion), and viscous fibrous properties (...more on that later as well).

I would really love to see some studies related to glycemic index of grain-free petfoods.  Most of these are made with potato starch, because a good deal of starch is needed for the extrusion process in order to hold the kibble together.  I'd like to see this because I suspect that many of the grain-free foods made with potato, will actually cause a higher glycemic index (this may be a good thing for those of you with dogs that are prone to collapse at trials or during intense exercise but may be a concern for overweight cats prone to diabetes).   Interestingly, some groups in Canada are studying the increased use of peas and pea starch in petfoods.  Like barley and oats, peas have some really awesome fiber characteristics as well and the resulting glycemic index is much lower than rice or potato. I love peas (for me and the dogs!)

My dogs are fed extremely varied diets included raw, home-cooked (quite literally the only thing I cook), kibble, canned, dehyrated and combinations of all of the above.  I am fortunate they don't have issues with grains or carbs; therefore,  I can and do provide varied sources.  In my raw and cooked diets, 30% of the diet is a carbohydrate mix that includes fruits, vegetables, greens, and grains (barley, oats) in equal proportions by weight. I do not include potatoes in my blend but will on occasion include corn (especially in the summer when I can buy it fresh). I bet you wondered if I'd say the "c" word.  Absolutely, I will use corn in moderation just like the rest of my carb sources.  I try to add at least 3-5  different fruits and vegetables in every batch (typically 2 weeks worth of food).  I do buy what is seasonal (I am an Animal Scientist after all, and "least cost formulations" are important to me).

If any of my dogs seemed to have issues at trials or during exercise with hypoglycemia or collapse, I would actually utilize some of the higher protein and fat (maintaining a 2:1 protein to fat ratio) diets that have rice or potato listed in the top 5 ingredients (many many options).  I would use these throughout trial weekends, along with my raw diet and if the dogs were agreeable, I'd use them as treats (perhaps make meatballs with ground up kibble and raw meat...a little honey added if Keegan were the chef) throughout trial weekends. This might take some trial and error to see what worked best but that would be my plan A (I don't come up with Plan B until I need it)!

Cheers!!!