Hey Arrow, the beet pulp is just an insoluble fibre I would think. They do need some of that and it's not likely a carbo source.
Fact is, meat and fat are expensive and carb's are cheaper. That's why they use so many. There are new "evolutionary diets" out now that are "grain free".
Look for foods that have prebiotics and probiotics in them too, yucca shidigera is a common one in pet food. The top foods are made to consider all of the amino acids and so on. I personally would not feed Iams FYI. We did a test with our own dogs (we have 4) and we moved from a high end holistic food to a cheaper well know brand sold in supermarkets. It was less than half the price.
Anyhow, some of the dogs appeared to be OK but one developed a problem with incontenence within 8 weeks. We put them back on the original food and the problem went away within 3 weeks. Amazing. They do stuff in the foods that plays games with natural digestive processes. For example, a well known brand of cat canned food uses a chemical additive to lower urine PH. (After cats eat the urine PH spikes). Anyhow, the natural evolution of cats would see them eating meat mostly (a cat is called an "obligate carnivore" which means they MUST have meat - kind of like my brother
). Natural meat diets naturally keep the urine PH at proper levels and prevent the spike. The chemical manipulation has a side effect whereby the urine PH falls too low after the bulk of the meal is metabolized and too low of a urine PH is no good either (it's called acidosis). So, this example demonstrates how feeding whole ingredients that mimic the evolutionary diet of the animal naturally works with the whole dietary management of the dog / cat.
In the past pet food companies started using too many carbs for cats and the result was that cats developed health problems due to too few amino acids found in meat. Example: Taurine, cats were losing heart and eye function due to not enough taurine. Well, you can stick meat in your food to fix that problem or you can add taurine and still use grains. Obviously the meat solution would be preferred.
Dogs are true omnivores so there should not be anything wrong with them eating some carbo sources.
The key is a high quality balanced diet.
Regulations are not helpful either - there are rules about what you can say on product labels that help companies hide quality facts from consumers. By law you have to call X ingredient "by product". Well, you can buy really really good by product and you can buy really really crappy by product. The nutritional contribution would be quite different between the two but on the label they must be called the same. The consumer would never know. Better manufacturers stick to quality of ingredient as much as the ingredient itself. One of the threads mentioned Royal Canin. I've been to their plant, it is something right out of NASA. Amazing. The make ingredient haulers wait while they do a sampling of the profile of all ingredients they receive. If the profile of the new batch is not identical to the biological profile of the spec, the reject it. Other vendors buy X ingredient and go by price. One day for X$ a ton they get good quality X, another day they get lower quality X for the same price and the end result is a food that has inconsistent quaility.
It's a huge riddle just like we have for human food. Sorry for the ramble, I could go on for days on this.
Jim