Pet Rabbit Awareness Week 2014
Pet Rabbit Awareness Week 2015
Phone: 9317 6615

Pet Rabbit Awareness Week 2014

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Research on Muesli Diets

The project was conducted by The University of Edinburgh in conjunction with Burgess Pet Care, and looked to investigate the effects of diet on the health and behaviour of pet rabbits.

The key findings from the research suggest that feeding muesli-style diets to rabbits is associated with abnormalities that can lead to painful dental and digestive problems, such as dental disease, lower gut motility, selective feeding, obesity and urinary tract stones or sludge.

The feeding trial was carried out at The Food and Environment Research Agency (FERA), and was subjected to rigorous controls by the University of Edinburgh Veterinary Ethical Review Committee and the Ethical Review Committee at FERA. At all points during the trial the rabbits were monitored by FERA's professional team. The welfare of the rabbits was of paramount importance to all involved in the trial.


There were 32 Dutch rabbits (20 male, 12 female) chosen to take part in the feeding trial; this breed was chosen specifically as it does not have a predisposition for developing dental disease. The rabbits were housed in pairs, under controlled conditions of temperature, light and humidity. Shortly after their induction into the feeding trial all of the rabbits were vaccinated against myxomatosis and viral haemorrhagic disease, and neutered.

Once inducted onto the trial the rabbits were transitioned over a two week period onto their trial foods. There were four groups in total:

  1. Hay only (HO) being fed ad lib Timothy hay;
  2. Nugget and hay (NH) being fed 50g of nuggets and ad lib Timothy hay;
  3. Muesli only (MO) being fed 125g muesli; and
  4. Muesli and hay (MH) being fed 60g muesli and ad lib Timothy hay.

Dental Health

Rabbits have open rooted teeth that grow continuously throughout their lives, and so require regular wear from fibrous material.

Dental disease in rabbits may be congenital or acquired, with acquired being the much more common presentation.

  1. Congenital dental disease occurs as a result of the lower jaw being longer than the upper (Mandibular prognathism), seen commonly in dwarf breeds with short faces. Primary malocclusion of the incisors may also occur.
  2. Acquired dental disease occurs most frequently from inappropriate diets resulting in insufficient wear of the teeth. Over time the cheek teeth become overgrown, resulting in curvature of the teeth and changes to the surrounding bone. As a result secondary malocclusion of the incisors may occur. Low dietary calcium is also thought to play a role in the development of dental disease.  Jaw or tooth fractures, as a result of trauma may result in dental disease.

During the feeding trial the rate of growth and wear / attrition of the incisors were measured. It was found that the rate of growth matched the rate of attrition across all of the groups i.e. the more the teeth were worn down the faster they grew to balance this. The rates were highest in the HO group in correlation with their fibrous material intake. The MO group had the lowest rates.

During the feeding trial the rabbits were radiographed at three time points: at the time of neutering, at 9 months and 17 months. The rabbits were wrapped in towels and the radiographs taken with a horizontal beam, which eliminated the need for any general anaesthesia. Measurements were then taken of the teeth from the radiographs.

It was found that across all of the groups the cheek teeth were similar lengths when straight line measurements were taken. However it was noted that in the MO and MH groups the first premolar teeth became significantly curved, and so were significantly longer than those of the HO and NH groups. Calculations were made to measure the length of the curved teeth, and to assess the angles of the curved teeth, and it was noted that in the MO and MH groups the teeth were longer and more curved than the HO and NH groups.

It was also found that the roots of the cheek teeth of the MO and MH groups started to splay outwards and the spaces between them widen instead of growing parallel to each other. Again calculations were made of the angles between the teeth, and it was found that there were significant levels of splaying or widening of the tooth roots in the MH and MO groups.

Radiographic evidence of tooth curvature and root splaying are classed as pre-clinical evidence of dental disease, and if allowed to continue on their current diets the affected rabbits are very likely to have developed clinical dental disease. The results suggest that feeding a muesli-style diet can lead to clinical dental disease and that feeding hay does not counteract the negative effects of feeding muesli. The fact that these changes occurred in less than 2 years is very significant.

Digestive Health

Rabbits are fibrevores and have a complex gut developed to digest fibre. Fibre is classed as either digestible or indigestible. Indigestible fibre maintains the motility of the gut, and is excreted from the body in the hard round pellets (normal droppings). Digestible fibre is fermented within the caecum in a process that allows the rabbit to extract nutrients and energy from it. This is excreted from the body in the soft sticky faeces termed caecotrophs. 

These are consumed directly from the anus once or twice during a 24 hour period. The normal production of faecal material is used as a mechanism to monitor gut health and function.

Over the course of the feeding trial it was found that the MO and MH groups produced faecal pellets that were smaller, lighter and in lesser numbers that the NH and HO groups. There was a direct correlation between hay intake and faecal output. This is significant as it suggests that the MO and MH groups had slower functioning guts, with lower motility. This could leave them at higher risk of developing gastrointestinal stasis, a serious condition when the gut stops moving and functioning. It also suggests that feeding hay does not counteract the negative impact that muesli has on this aspect of digestive health.

The MO and MH groups were also found to have a significantly higher number of uneaten caecotrophs over the course of the feeding trial. As previously mentioned caecotrophs are soft and sticky and when uneaten will often stick to the rabbit and the hutch. 

They are difficult and unpleasant to clean from both the rabbit and the hutch. This not only puts the rabbit at risk of developing dermatitis and fly strike but also risks breaking the pet owner bond. In addition, not consuming caecotrophs could result in a lack of nutrients, as they provide a vital source of B complex vitamins, vitamin K and energy.

Selective Feeding

When fed a muesli-style diet, 100% of the rabbits selectively fed. Both MH and MO groups left behind the pelleted components, which are the high fibre elements of the diets. Even when the muesli was left for as long as possible in the housing the rabbits resisted eating these components. The significance of this result is that it negates the argument that 'feeding muesli provides balanced nutrition' as rabbits do not consume the entire diet. Selective feeding results in the animal selecting the high starch elements of the diet and leaving behind the much needed high fibre elements. 

What's more, when faced with this situation pet owners tend to either re-fill the bowl to counter this, or, if they do not re-fill, could risk the health of the rabbit by leaving them too long without food, which is dangerous.

Hay Intake

Feeding a muesli diet was also found to result in a lower hay intake, even when hay is fed ad lib, than feeding an extruded nugget diet. Hay is a vital component of the diet of a rabbit to maintain dental, digestive and emotional health. Reduced hay intake could also exacerbate the other health conditions outlined above.

Weight and Body Condition Score

Throughout the feeding trial the rabbits were weighed on a weekly basis and body condition scored (BCS). Over the course of the feeding trial trends developed in terms of weight gain and BCS.

The MO group gained weight rapidly, and reached above ideal body condition scores. This led to the conclusion that feeding muesli alone leads to obesity in the rabbit, thus making the rabbit more susceptible to obesity related conditions such as flystrike, pododermatitis,joint disease, and metabolic disease.

The HO group remained lighter in bodyweight, and never reached breed standard. Although none of the rabbits were too thin, this led to the conclusion that feeding a hay only diet can result in less than ideal body weight. This raises the question that, over time could this result in malnutrition from a lack of vital nutrients, given the variation in quality of hay available commercially?

The NH and MH groups gained weight at a steady rate, did not become obese, and their weights were similar in both groups over the course of the feeding trial, leading to the conclusion that feeding a concentrate diet with a high quality hay results in steady weight gain in a growing rabbit, and aids in the prevention of developing obesity.


Following the trial there is now statistically significant evidence that feeding a muesli-style diet, with or without hay, can result in an increased risk of dental and digestive health problems such as:

  • Poor gut motility, which can put rabbits at a high risk of gut stasis, a condition which is often fatal
  • Eating less hay, which can lead to abnormal growth of teeth that could develop into painful dental disease. Lower hay consumption also results in reduction in water intake, which in turn could lead to urinary tract stones or sludge.
  • Not eating all their caecotrophs, meaning they may not get all the nutrition they need and uneaten caecotrophs may become matted in rabbits' fur, putting them at risk of dermatitis and fly strike
  • Selective feeding (where rabbits pick out their favourite pieces rather than eating the whole portion), which can lead to an imbalanced diet lacking in vital vitamins and minerals.
  • The research has also shown that eating muesli-style foods without hay causes rabbits to become overweight or obese, which can also lead to health problems.