This week we’re covering more on commercial foods. How does freeze-dried compare to air-dried and what about cold pressed? Plus, how much veggies should dogs eat? The answers from self-proclaimed experts are all over the place, but what does the science say? Before that here are this weeks recipes:
Freeze-dried, air-dried, cold-pressed
With so much variety and different ways to make dog food it’s starting resemble the coffee industry. There are people who swear by Folgers, while more selective drinkers might only take cold brew or pour over coffee. The connoisseurs, however, have very sophisticated equipment to do things like evenly distribute the beans and ensure every grain of coffee gets the same contact with water. But ultimately, the end result is similar…a cup of coffee. If you use crappy beans or burn the beans while roasting, no amount of fancy gear will make it good. Any food is the same.
It’s probably clear that we prefer fresh, homemade food. Nutrients are the most bioavailable, and we can ensure the freshness of the ingredients before it gets mixed together. But, freeze dried, air dried or cold pressed all can make good food. These processes use temperatures that are lower than extruded kibble. Lower temperatures means that more of the nutrients are retained.
Ultimately what’s most important is the quality of the ingredients.
If you missed the post on the importance of human grade foods, see that here. The main issue with animal grade products is the lack of enforcement by authorities. The FDA basically says that it doesn’t have resources to make sure dead and diseased animals don’t get into the pet food supply. It’s not just that they are dead or diseased that matters. It’s what happens to the animals when they are dead and diseased. Tranquilizers used to put down animals are routinely found in pet food supplies as well as far higher levels of contaminants like mycotoxins (from molds) that occur when food rots. Mycotoxins are believed to cause cancer.
So which type of food is better? It really depends on the manufacturer and their process, but if we had to force a ranking it would be: freeze dried is probably best, followed by air dried, with cold pressed being very close to air dried and in some cases better than air dried. Here’s why.
Freeze dried:
Freeze dried foods are made by freezing and then placing the frozen food in a cold vacuum chamber. Removing the air from the freeze drier helps to speed up the drying process (water turns into gas to fill the space). This is why freeze dried food is often fluffier and has more air in it, it’s dried with little air pressure.
The moisture content of freeze dried foods is very low (around 1%) so freeze dried food can be rehydrated for best results. Freeze dried meals can also be fed without rehydrating, but it’s important to make sure your pet has enough water.
The research shows that freeze dried foods retain more of their nutrients than dehydrated foods. The difference can be very large depending on the air drying process. See below.
Air dried:
Air drying is a general term for using low heat to dry food, but the temperature manufacturers use to dry their foods can vary. Since heat can degrade nutrients, the lower the temperature, the better the product. However lower temperatures take longer and are more expensive. There are protocols for drying foods at temperatures between 40° - 80°c or more. Since this is often unpublished it’s hard to know at what temperature any air dried food is actually processed.
When comparing freeze dried foods to air dried foods the vitamin content of vitamin c is as much as twice as high in freeze dried foods. See this analysis here. Also, fats can be altered in the air drying process, especially polyunsaturated fats that are more unstable.
Cold pressed:
Cold pressed is relatively new to pet food. Because it’s not a specific process, unlike freeze drying, and similar to air drying, there is a lot of variability in the end product. Raw ingredients are ground, mixed and then pressed together at temperatures that are typically below 45°C (113° F). This is cold for processing food, but not cold in terms of refrigeration or living conditions.
After the pellets are formed they often undergo a separate drying process to remove excess moisture and preserve the food. This drying process is similar to air drying.
Because of the low temperatures used, the potential exists to harbor bacteria. Since several brands of kibble extruded at high temperatures have previously been recalled for salmonella contamination, both the manufacturing process and quality control are even more important for this type of food.
Conclusion:
Freeze dried foods are the best in terms of nutrient retention, shelf life and safety. Air dried and cold pressed foods have higher variability in their manufacturing processes compared to freeze dried foods with cold pressed foods also having moderate safety concerns.
What percentage of my dog’s diet should be veggies?
If you do a google search on “how much veggies should dogs eat” you get a wide range of answers. Some sites say 10% of their diet should be veggies (I’m not sure why Forbes is my top search result), others say 20%, while some Instagram vets say 30%. So who’s right? Probably none of them.
Why? First, Anyone who definitively says a number like 20% is just making stuff up. The only way to get that specific would be a study that tests different veggie amounts and then measures an outcome like lifespan or energy output. To our knowledge, no one has done that study. But, we’ve previously cited one study that showed working dogs performed best on a very low carb diet (<1% carbs, meaning very little veggies). Does this mean all dogs should be on that diet? Probably not.
Which leads to the second point, there is a lot of variance between dogs, from life stages, to activity, to preference, to digestive issues. Some dogs hate vegetables, but Cedric and Edith love them. Some dogs are allergic to all sorts of proteins and can only eat lamb, for example.
So what does the science say about how much veggies dogs should eat? It doesn’t say anything. Since we couldn’t find any papers comparing vegetable content in dog diets, we looked at other studies that examined vegetable digestibility in the guts of dogs or how fiber affects digestibility. One well conducted study looked at the products of vegetable fermentation in dog digestion including gas (neutral) and short-chain fatty acids (good). The conclusion of the authors is that a reduction in insoluble fiber increases the amount of short-chain fatty acids which have many health benefits like anti-inflammatory, heart and liver protective properties. In other words a higher ratio of soluble fiber (like those found in fruits) to insoluble fiber is better.
Another high quality study from 1982 on kibble used increasing amounts of insoluble fiber (the main fiber in leafy greens) to determine the effect on digestion. Researchers concluded that higher levels of insoluble fiber reduced digestibility and reduced transit time (time to digest food). Three percent insoluble fiber had 90% dry matter digestibility while nine percent insoluble fiber had only 70% dry matter digestibility.
Ok, so what does this mean? It’s likely that maintenance diets should be on the lower end of insoluble fiber for maximum digestibility. That means leafy greens are great but should be a smaller proportion of a dogs vegetable intake. Vegetables like carrots, broccoli, sweet potato and beets should make a larger portion. Fruits like pumpkin, apples and berries also contain higher levels of soluble fiber and make a great addition to your dogs diet.
That’s it for this week.
All the best,
Joelle & thecedlife fam
Thank you, I really appreciate all of the research you do...I read all and understand what kind of time you put into all.
Your knowledge is so helpful and Cedric and Edith steals your heart:)