Petfood labels declare the food's content of crude fiber, which mainly comprises cellulose, hemicelluloses and lignin. Research on diet and feline hairballs has concerned three fiber sources, purified cellulose, dried sugar-beet pulp and psyllium husk. These ingredients contain about 65, 19 and 3% crude fiber, respectively.
In a double-blinded, cross-over study, a chew containing psyllium husk and slippery elm bark reduced vomiting, retching and coughing (4). Total symptoms fell from 2.3 to 1.7 times/week/cat. The 16 long- and 8 short-haired cats affected with hairballs were fed the 2-g placebo or test chew twice daily in addition to their normal diet for two weeks.
Cats (n = 102, 47 households) were fed a dry maintenance diet or a similar diet with added fiber in a cross-over study with periods of 60 days (5). Details on coat length distribution and diets are not given. The number of hairballs and vomiting frequency reported per household were each reduced by 22% while cats were on the fiber-enriched diet.
In a double-blind, parallel study lasting 28 days, cats consumed a dry food with 4% powdered cellulose or the control diet (1.8% crude fiber) containing corn in place of cellulose (6). Cats (n = 12/group) were stratified according to hairball episodes and hair length. Owners recorded vomiting, retching and coughing. Dietary cellulose decreased group-mean total signs from 2.5 to 0.5 times/week/cat.
Fecal hair excretion
Cats excrete trichobezoars, compact masses of hairs (7). Hairs can be separated from feces by sieving and washing steps. Compared with 2.0% crude fiber in dry food, levels of 4.5 and 7.8% raised fecal hair loss by 26 and 72% (8). Diet compositions are undisclosed. Adding 0.5% psyllium husk and 5.2 or 9.7% cellulose to a dry diet (1.2% crude fiber) induced a 1.8- and 2.2-fold increase in fecal hair excretion by long-haired cats, but was effectless in shorthairs (2).
Replacing wheat meal (1.75%) or beet pulp (2%) in dry food by cellulose increased group-mean fecal hair by 62 (9) and 15% (10). Cats on a dry diet containing 13% cellulose excreted 2.7 times more hair than did cats fed a diet with 12% beet pulp (11). Replacing 10% corn in dry food by sugar-cane fiber lowered group-mean fecal hair excretion by 9%, whereas cellulose as substitute raised it by 29% (7). Beet pulp (8 or 16% in dry food) versus corn reduced fecal hair excretion by 18% in short-haired cats (12). Dietary Miscanthus grass did not affect fecal hair loss (13).
The data indicate that dietary cellulose stimulates fecal hair excretion and reduces hairball symptoms in cats. At unchanged fur ingestion, increased fecal hair loss infers decreased formation and vomiting of gastric hairballs. Thus, cellulose would push or pull gastric hair into the duodenum. There is no convincing evidence that dietary crude fiber accelerates gastric emptying in cats (14-16).
Cellulose fibers might prevent agglomeration of single hairs in the stomach, thereby propelling loose hairs into the duodenum (17). Untangled and lengthy cellulose fibers would then be most effective. Cellulose is neither digested (18, 19) nor fermented (20, 21) in the feline digestive tract. The fiber may increase bulk and passage rate of digesta, thereby lowering the risk of clinical intestinal hairballs.
Dry anti-hairball foods of 12 different brands declare crude fiber levels of 3 to 11%. The ingredient statements of five foods list cellulose. Six wet, cellulose-containing foods have 6 to 14% crude fiber in the dry matter.
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