Sugar beets (Beta vulgaris var. altissima) are grown around the globe and are a valuable option in modern crop rotation strategies. Last year, US farmers harvested 29.9 million tons of sugar beets on 1.3 million acres. Over the past 10 years, sugar beets accounted for more than 53% of US sugar production.
Sugar beets are tubers that grow in the ground much like garden beets, carrots or turnips. In autumn, farmers "campaign" or harvest the sugar beets by unearthing the tubers and trucking them to processing plants, where they are dumped in mountainous piles waiting their turn to be processed. First, dirt and debris are sifted and washed from the surface and the sugar beets are sliced into cossettes (chips). These cossettes are then steeped and (or) washed with hot water in countercurrent flow diffusers to extract the sugar. The extracted juice is further processed to produce granulated sugar suitable for the sweetener market and the residue (pulp) is dried. For ease of transportation and handling, most of the fibrous beet pulp is milled into 3/8-inch diameter pellets.
The gray, speckled pellets are sold primarily into the livestock feed market and have found favor in dairy cattle and horse diets as "dried plain beet pulp" (Section 60.36; AAFCO 2005 Official Publication). Some beet fiber has begun to find its way into human foods with such disparate applications as decorative sprinkles on baked goods to supplemental fiber laxatives. This latter application is where beet pulp has found favor in petfoods, as a supplemental fiber source to promote bowel regularity, stool consistency and overall gastrointestinal (GI) health.
Physiological effects
Regularity or laxation from fibers is attributed, among other things, to "bulking" and water-binding capacity in the lower GI. These combine to increase GI luminal contents and stimulate gut motility. One would predict that beet pulp, with its high concentration of total dietary fiber (TDF >65%) and substantial water-holding capacity (>6 g H2O/g DM), would fulfill this role quite nicely. This was confirmed in early dog nutrition work in which a linear increase in wet fecal excretion and defecations per day resulted from increasing levels of beet pulp in the diet (Fahey, et al., 1990). A similar effect was demonstrated in the cat (Sunvold, et al., 1995b). Contrary to what often occurs with supplemental fiber sources, elevated levels of beet pulp (12.5% and 7.5% in the dog and cat, respectively) were not reported to negatively affect palatability.
The challenge is that digestibility declines with the inclusion of beet pulp beyond about 5% of the diet. However, compared to non-fermentable fibers like cellulose, this decrease in digestibility is much smaller (Muir, et al., 1996). An offset to this negative is that beet pulp is fermented to a limited degree in the colon. Results from in vitro fermentation of beet pulp with dog and (or) cat fecal inoculum ranked beet pulp more fermentable than cellulose, and about a third as fermentable as extremely-fermentable substrates like guar gum (Sunvold, et al., 1995a). Thus, it is often described as "moderately" fermentable.
This results in a slight shift in the fermentation end products to a greater proportion of the short-chain fatty acid, butyrate. Butyrate is a key fuel for the coloncyte. Improvements in colonocyte microstructure health were credited to this change in fermentation end products when dogs were fed beet pulp-containing diets (Hallman, et al., 1995) and would tend to refute some of the anecdotal claims that beet pulp causes "plugging" of the intestinal villi. Additionally, beet pulp has found favor as a key ingredient in hairball remedies; as a way to attenuate the glycemic response in diabetic diets; as an energy diluent in "Lite" diets; and has been claimed to improve gut immune response.
Consumer perception
There has been some confusion by consumers regarding beet pulp; primarily as it relates to the name and the plant's origin. First, consumers have confused beet pulp with the common red beet. Because of this confusion, beet pulp has been blamed for red stains around the mouth of light colored dogs and carpet stains due to inappropriate elimination. However, both of these faults are misdirected, as beet pulp really has no pigment, especially not red. Secondly, some consumers have mistakenly assumed that a substantial amount of sugar remains with the pulp and they don't want sugar in their pet's diet. However, this concern is not well founded, as only trace amounts of sugar remain with the pulp. Bloat and villi plugging have also errantly been blamed on beet pulp without good cause.
A great deal of research and information has been published regarding the merits of moderately-fermentable fiber from beet pulp in companion animal diets. Despite this effort, there are some consumers who consider beet pulp as less than desirable due to its perception as a low-grade filler, livestock feed or their misplaced health concerns. Further, long-term clinical studies which directly demonstrate that beet pulp is superior to other fiber sources on GI health are lacking and might improve consumer acceptance of functional fibers, like beet pulp, in their pets' diets.
