Understanding Fiber in Laboratory Rodent Diets - Definitions, Measurements, and Adjustments

The effects of fiber in health and disease is an active subject of research in a range of research areas. Historically, the definition of fiber has been subject to change and refinement due to greater understanding of physiology and analytical method development.

 

There are two major types of laboratory rodent diets. Standard natural ingredient diets or "chows" are fed to maintain animal colonies and at times are fed as control diets. These diets are comprised of grain ingredients and other agricultural commodities and contain a range of complex plant polysaccharides and fiber. In contrast, purified diets use highly refined ingredients such as casein, corn starch, sucrose, etc., that allow for the precise control of nutrient levels and limit non-nutritive factors. These types of diets are lower in fiber, typically only containing 0-8% cellulose. Understanding the differences in these two types of diets is important for reading and interpreting research in many different areas.

 

There are three fiber measurements often reported on standard diet data sheets. These include neutral detergent fiber (NDF), acid detergent fiber (ADF), and crude fiber. Understanding these values is important in interpreting fiber levels within a diet. Despite the recent recognition of the importance of soluble fiber in humans and other non-ruminants, information on soluble fiber in rodent diets is lacking.

 

Custom fiber adjusted diets typically start with a purified diet to which other fiber source(s) are added. Inclusion rates of 5-10% are typical. Higher inclusion rates are possible but the physical characteristics of the diet and possible gastrointestinal problems should be considered.

 

Learning Objectives