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The role of dietary fiber in elimination of hair from the digestive tract

Weber M, Sams L, et al.  Influence of the dietary fibre levels on faecal hair excretion after 14 days in short- and long-haired domestic cats.  Veterinary Medicine and Science 2015;1:30-7.

Although hairballs (trichobezoars) are a common problem in pet cats, there is no published data regarding the incidence of hairballs in cats. Grooming behavior may occupy 25-30% or more of a cat’s waking time, and during self- or allogrooming sessions, a large amount of hair may be ingested.  Much of the ingested hair is eliminated in the cat’s feces, but some may accumulate in the digestive tract and form hairballs, which can result in a gamut of problems including vomiting, abdominal pain, constipation, anorexia, or even intestinal obstruction requiring surgical intervention.  Long-haired cats that live mostly or completely indoors are most likely to have health problems associated with hairballs, particularly in the spring and fall when shedding (moulting) of the haircoat occurs.

Many cat owners and veterinarians resort to dietary therapy to ameliorate health problems associated with hairballs.  Diets designed to reduce the incidence of hairballs usually contain increased levels of soluble and/or insoluble fiber, which is considered to promote the passage of ingested hair through the gastrointestinal tract and elimination of the hair in the feces without causing obstruction, constipation, or formation of hairballs.  This study, performed in the Northern Hemisphere summer months of July to September, when cats are not in a haircoat moulting period, was designed to evaluate the influence of psyllium and different levels of total dietary fiber (TdF) on fecal excretion of hair in short-haired (SH) and long-haired (LH) domestic cats.

The study included 21 healthy adult research cats. One group (n = 7) was designated as a shedding panel, used to assess fur shedding throughout the study, and was composed of 3 LH cats and 4 SH cats.  A panel of 7 SH cats and another panel of 7 LH cats were used to assess the impact of the diets tested on fecal hair excretion.  Of the 21 study cats, 10 were female and 11 were males, and were sex-matched across groups; all were neutered and the median age was 4 years (range, 2-11 years).  All cats were clinically healthy based on physical examination, were treated monthly with a topical flea and tick ectoparasiticide, and were housed in closed indoor and outdoor runs with unlimited outdoor access.  The cattery was maintained at a constant temperature and the cats were exposed to a normal day length and natural lighting during the study. In each phase of the study fecal hair excretion was quantified daily for each collective panel of cats.

Three diets, all dry, expanded, complete and balanced adult feline maintenance diets which varied in TdF and psyllium contents were utilized in the study.  The control diet (diet 6) was a low-fiber diet (6% TdF) and no psyllium.  One test diet (diet 11) had moderate TdF (11%) and 0.5% psyllium husk, and a second test diet (diet 15) contained high TdF (15%) and 0.5% psyllium husk.  The TdF in the two test diets was increased by supplementing the diets with cellulose.

The cats of the shedding panel were brushed three times a week and the hair collected was weighed to quantify shedding over the study, which was divided into four 14-day long phases.  A week prior to starting the study the SH and LH panels underwent a 3-day purge to eliminate hair accumulated in the digestive tract. In phase 1 both panels were fed the control diet for 14 days; in phase 2 both panels were fed either diet 11 or diet 15.  In phase 3 all the cats were again fed the control diet for 14 days, and then in phase 4 they crossed over to the other test diet (diet 15 or diet 11) in phase 4.  The first 3 days of each phase involved gradual food transition to avoid digestive disturbances from abrupt diet changes.

Results of the study showed that fecal hair excretion by the shedding panel demonstrated that the study did not occur during a shedding season. With regard to fecal hair excretion by the SH and LH panels, these researchers determined that the impact of dietary fiber level on fecal hair excretion varied according to haircoat length.  The LH panel of cats had significantly higher fecal hair excretion with diets 11 and 15 compared to diet 6; therefore, the combination of psyllium and cellulose facilitated fecal hair elimination in LH cats.  A diet with 11% TdF appears to be adequate to stimulate fecal hair excretion in LH cats, as no significant difference was found in the quantity of fecal hair excretion in LH cats whether they were on diet 11 or diet 15.  The SH panel demonstrated similar quantities of fecal hair excretion when fed any of the three diets. When this group was fed diet 15, the highest daily fecal hair excretion was equivalent to the lowest fecal hair excretion in LH cats.

Limitations of this study included the small number of cats and the relatively short duration of the study and each of its phases. It is possible that the diets could have had a significant impact on fecal hair excretion in SH cats during the shedding season, but the study did not extend into a shedding season. The diets fed did not vary in the percentage of psyllium included, so the study could not determine which of the two fiber sources (psyllium or cellulose) has the greatest effect on fecal hair excretion in cat feces. While the provision of dietary fiber sufficient to potentiate fecal hair excretion in cats may be helpful in preventing health complications from hairballs, it is important for clinicians and cat owners to be aware that vomiting and other complications from frequent hairballs should not be trivialized but should prompt a search for underlying disease, especially of gastrointestinal etiology. [PJS]

See also:

Cannon M.  Hair balls in cats, a normal nuisance or a sign that something is wrong.  J Feline Med Surg 2013;15:21-9.