When considering the fiber and nutrient content of laboratory diet for your rodents, it is important to understand the differences between a natural ingredient diet and a purified diet. 

Fiber in natural ingredient diets
RMS Black rat Teklad

A natural ingredient diet — also called a grain-based diet or “chow” diet — often includes ground wheat, ground corn, wheat middlings, dehulled soybean meal, corn gluten meal, soybean oil, vitamins, and minerals. These diets, both custom and standard, are largely made of grains and soybean meal; however, they may also include alfalfa meal, lesser amounts of salt, and animal byproducts, such as fish meal or pork fat.
“In these types of diets, each primary ingredient contributes to a mixture of macronutrients, micronutrients, fiber, and non-nutrients,” explained Derek Martin, PhD, RD, Animal Laboratory Nutritionist at Envigo–an Inotiv company. 

The grain ingredients used in natural ingredients diets are rich in complex plant polysaccharides and fiber, both insoluble and soluble types.
“Fiber is not an ingredient in standard diets,” he added. “It's for this reason that we can't remove fiber or other nutrients. We will often be asked to make a diet deficient in some nutrient, amino acid, or fiber based on an animal facility diet, but it’s not possible.”

Dr. Martin notes that natural ingredient diets will have some inherent variability in nutrient and non-nutrient content due to various environmental factors. This means levels of fiber, specific amino acids, minerals, or phytochemicals will fluctuate over time.

Fiber in purified diets 

Purified diets are made with more refined ingredients. Here, each ingredient typically provides primarily one nutrient. Common ingredients include casein, starch, sugars, cellulose, specific oils, vitamins, and minerals. The refined nature of this type of diet allows for more precise control over macronutrients, micronutrients, and fibers. In these types of diets, there are limited non-nutrients and variability is limited. 

In these diets, casein is the most common protein source; whey protein, isolated soy protein, egg white solids, or individually added amino acids may also be used. Carbohydrate is typically provided by cornstarch, maltodextrins, sucrose, or other available carbohydrate sources. While fat sources can vary, soybean oil is often included in many diets to supply essential fatty acids. In these types of diets, there are limited non-nutrients and variability is limited. 

The most common fiber used in purified diets is cellulose (an insoluble fiber); it is typically included at ~5-8% by weight of the diet. We also stock pectin and inulin (soluble fibers) that can be included in purified diets. Other types of fiber may also be included as customer supplied ingredients.

“Anytime you see a high fat diet being used, it is most likely a purified diet,” said Dr. Martin. “Similarly, the most straightforward way to investigate the effects of dietary fiber, particularly soluble fiber, is through the use of purified diets.”
Understanding the differences in diets 

In general, Dr. Martin recommends that customers be careful when drawing conclusions about specific nutrients when comparing a natural ingredient diet to a purified diet, as they represent two different dietary patterns. 

“When reading research study results, you’ll want to keep these differences in mind,” explained Dr. Martin. “If a control diet is reported, you’ll want to determine if it is an appropriate control — and if the conclusions are warranted. This applies to research about fiber, minerals such as iron, and research around obesity, atherosclerosis, or NASH. These details often go unreported in literature, which prevents other researchers from making their own interpretation. For example, if researchers are attempting to determine if the fat content of a diet was solely responsible for weight gain in the research models. It’s important to publish this information to ensure research reproducibility.” 

Creating custom fiber adjusted diets 

The same thought process must be considered when designing a custom diet. By working with a nutritionist, researchers can both determine how to best control the fiber composition in their diet and balance other factors to control overall nutrient composition. This will also ensure that diet can be made into a suitable format or shape and the physiological needs of the research model are met.  

Get more details on our high fiber diets by reading our white paper, watching our webinar, or contacting our one of our nutritionists

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