The Importance of Fiber on Digestion

By George F. Collings, Ph.D.

Most people clearly understand that adding fiber in the diet of an herbivore like a rabbit is very important. However, most people do not understand that all fiber sources are not the same and can lead to very different results. Each fiber source has different components and very different structures which can lead to a variety of physiological effects especially upon digestion. Some fibers can help to firm the stool of an animal whereas others can lead to the opposite effect: diarrhea. In an herbivore like a rabbit, diarrhea can lead quickly to death.

A well designed diet will provide the proper proteins, fats, carbohydrates, vitamins and minerals the rabbit will need for a healthy life. Most of these nutrients are absorbed in the small intestine of the herbivore however small amounts do move to the colonic region of the intestinal tract. Fiber also passes through the small intestine. It is this 'bypassing nutrition' that has a beneficial or deleterious effect upon the animal. In the hindgut or cecal-colon region of the intestinal tract, there exists a unique symbiotic fermentation relationship between the bacteria in the fermentation and the host herbivore. If the fermentation is properly functioning (being properly fed), beneficial bacteria help support a healthy intestinal tract and immune system. If the fermentation is not functioning properly, pathogenic bacteria can increase which can lead to major digestive upsets, poor performance and death. Unlike many other mono-gastric animals, a rabbit has very few beneficial bacterial to fight off pathogenic bacteria.This puts a rabbit in a major disadvantage compared to other animals.This is the biggest reason why picking fibers that support beneficial bacteria is a critical portion of building a good diet.

Unlike many other mono-gastric animals, a rabbit has very few beneficial bacterial to fight off pathogenic bacteria.This puts a rabbit in a major disadvantage compared to other animals.This is the biggest reason why picking fibers that support beneficial bacteria is a critical portion of building a good diet.

Fiber sources like alfalfa have been widely used in the diets of herbivores. While the quality may vary, the end result is a good quality fiber source. Beet pulp, the waste product of the beet sugar industry, provides unique fibers and sugars that improve beneficial fermentation and lead to firmer stools in most animals. Grass ingredients sources like timothy can do the same. However, fiber sources like wheat middlings/bran and soybean hulls/meal can upset the fermentation of beneficial bacteria. Soy products have high levels of two sugars (stachyose and raffinose) that change the fermentation to produce more gas. Ultimately, gas causes intestinal pain and upset.Wheat products (middlings/bran) contain fibers that reduce the beneficial fermentation and lead quickly to diarrhea.

The bottom line is this - without a properly functioning fermentation, the animal's health is compromised. Beneficial dietary fiber sources and a properly balanced diet is critical to maintaining this delicate balance.

Dr. Collings is currently General Manager of Nutrition Horizons (a Provimi Co.). He was recently VP of Science & Technology with AFB International. Before that he was VP of Research & Development at Sunshine Mills, Director of Nutrition at Hills Pet Nutrition and Research Manager for Ralston Purina. Dr. Collings is a board certified member of the American College of Animal Nutrition, a Certified Nutrition Specialist of the American College of Nutrition, a Professional Animal Scientist and a member of the American Society of Nutrition. He has developed and launched over 1,000 products for over 100 animal species including rabbits, guinea pigs and chinchillas. His research in these species was improving the intestinal physiology and immune function preventing diarrhea and improving overall health.