Reduction in grass eating behaviours in the domestic dog, Canis familiaris, in response to a mild gastrointestinal disturbance

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Abstract

Grass eating behaviour in the domestic dog may be related to gastrointestinal distress. To explore this theory, the current study observed grass eating behaviours in dogs fed a standard diet with and without supplementation of a fructo-oligosaccharide (FOS). The FOS diet temporarily induced loose, watery stools to simulate a mild gastrointestinal disturbance. During both FOS Diet and Standard Diet periods, dogs were presented with couch (Cynodon dactylon) and kikuyu (Pennisetum clandestinum) grasses, and the time spent eating grass and the number of grass eating and vomiting events was recorded. Our study found that dogs spent significantly more time eating grass when fed the standard diet and producing normal stools than when they were fed the FOS diet and producing loose stools, suggesting that dogs do not use grass to self-medicate a diarrhoeal gastrointestinal disturbance. However, this does not preclude that other forms of gastrointestinal disturbance may be self-medicated by grass eating behaviours. Importantly, dogs did not use grass as an emetic, as there were only two vomiting events and 374 grass eating events observed. Alternatively, the reduction in grass eating may be attributable to a feeling of satiety caused by the fermentation of FOS. For further clarity, future research should examine the effect of other gastrointestinal disturbances, such as constipation (hard, dry stools) or nausea, on grass eating behaviour in the domestic dog.

Introduction

Grass eating is a common behaviour in domestic dogs, Canis familiaris, but there is very little research on this behaviour (Lindsay, 2001). Bjone et al. (2007) conducted the first controlled experiment on grass eating behaviour. In particular, they investigated the pattern of grass eating during the day and the relationship between grass eating and the ingestion of food. Bjone et al. concluded that grass eating is influenced by satiety and time of day: the subjects were less likely to eat grass when they were satiated and the amount of time spent eating grass decreased throughout the day.

Bjone et al. (2007) suggested that grass may be seen as a food source despite dogs having almost no capacity to digest the plant fibre in grass (Case et al., 2000, NRC, 2006). Kang et al. (2007) suggested that plant eating is due to a dietary deficiency, particularly fibre. Other researchers suggest that grass may be used to self-medicate some form of gastrointestinal distress (McKeown, 1996, Overall, 1997) as an emetic (Fox, 1965, Thorne, 1995, Houpt, 2005) or a laxative (McKeown, 1996). However, no scientific research has investigated these claims and gastrointestinal distress is a broad term that could encompass many “digestive upsets,” such as nausea, constipation or diarrhoea. A diarrhoeal gastrointestinal disturbance can be readily induced in dogs by supplementing the diet with fermentable fibre (Flickinger et al., 2003, Twomey et al., 2003). Therefore, the effect of a mild diarrhoeal gastrointestinal disturbance on grass eating behaviours is investigated in the current study.

BeneoP95® (ORAFTI, Tienen, Belgium), formerly known as RaftiloseP95®, is a commercially available fructo-oligosaccharide (FOS) extracted from sugar beet. It passes undigested through the small intestine and readily ferments in the large intestine. BeneoP95® is sometimes included in commercial dog diets as a prebiotic to encourage the growth of beneficial bacteria in the colon (Fahey et al., 1990, Flickinger et al., 2003). In larger doses, FOS can degrade faecal consistency and induce loose, watery stools. Flickinger et al. (2003) noted that supplementation greater than 20% of dry matter in adjusted animals or greater than 10% in animals which have not adjusted to the supplementation may cause flatulence and loose stools. Therefore, 10% supplementation of BeneoP95® was used to induce a mild gastrointestinal disturbance (loose, watery stools) in the current study.

We hypothesised that a mild gastrointestinal disturbance of loose, wet stools would affect grass eating behaviours in dogs. In addition, we hypothesised that the dogs would prefer couch grass (Cynodon dactylon) compared to kikuyu (Pennisetum clandestinum) grass because dogs have been anecdotally documented to eat couch grass, which has the vernacular name “dog grass” (de Baïracli Levy, 1992, Engel, 2002). Both grasses have been used in previous research (Bjone et al., 2007).

Section snippets

Subjects and housing

Twelve beagles (three males; nine females) of similar age (mean ± standard error (SE) = 3.7 ± 0.5 years) and weight (mean ± SE = 13.3 ± 0.3 kg) were housed at the University of New England Dog Research Facility (Armidale, New South Wales, Australia) in individual pens for the duration of the study. Dogs slept on trampoline style beds within the secure, centrally heated facility at night. During the day, dogs were placed in spacious, fully covered, outdoor runs and were socialized and exercised in compatible

Results

The study dogs readily ate both the standard and FOS diets and there were no food refusals. Faecal scoring during the Standard Diet periods verified that all dogs were producing normal stools when fed the standard diet (mean ± standard error (SE) = 2.0 ± 0.1 faecal consistency scores) with a mean dry matter content of 52% (SE = 1%). The FOS diet did induce loose, watery faeces as exhibited by significantly greater faecal consistency scores (mean ± SE = 3.8 ± 0.1; F(3,33) = 205.1, P < 0.001, pη2 = 0.95) and

Discussion

Supplementation of the standard diet with 10% BeneoP95® did create looser, wetter stools compared with the dogs’ stools when fed the standard diet. Following supplementation with the FOS, loose stools appeared the following morning (before behavioural observations) and persisted through the afternoon feeding. Therefore, observations of grass eating behaviour coincided with the dogs exhibiting normal stools during the Standard Diet period and symptoms of a mild gastrointestinal disturbance,

Conclusion

In conclusion, the FOS diet did induce loose, watery faeces as exhibited by significantly greater faecal consistency scores and significantly reduced faecal dry matter content. The dogs spent less time eating grass and demonstrated fewer grass eating events when they had a mild gastrointestinal disturbance compared with when they produced normal stools, suggesting that they did not use grass to self-medicate a diarrhoeal gastrointestinal disturbance. However, this does not preclude that other

Acknowledgements

Thanks to Sara Butler and Dharma Purushothaman for their reliable and invaluable assistance throughout the experiment.

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