Part 3.1 Nutrition
This is Part 3.1.1 of the Code of Practice for the Housing and Care of Laboratory Mice, Rats, Guinea Pigs and Rabbits.
All four species practice coprophagy — the ingestion of a special faecal pellet coated in mucus. They are cautious feeders, often avoiding unfamiliar foods.
These animals have constantly erupting teeth and interference to wear will lead to malocclusion, which causes difficulty with eating and swallowing.
Guinea pigs are unable to synthesise Vitamin C (ascorbic acid) in sufficient quantity to meet their daily requirements. Insufficient Vitamin C intake will lead to debilitation, increased susceptibility to disease and eventually to scurvy.
Guinea pigs, in particular, do not like change in their diet.
Minimum standards for nutrition:
- Laboratory animals must receive a palatable diet, which is free from contaminants and provides the nutritional requirements appropriate to the species, age and breeding stage of the animal.
- Food must be stored in cool, vermin-proof rooms under conditions that prevent it from becoming a health risk to the animals.
- Communication between investigators and animal house staff must be maintained concerning any supplementation or manipulation of diets.
- Diets for guinea pigs must fulfil their Vitamin C and E requirements.
- Consideration must be given to the type of presentation of food when feeding young or handicapped animals.
- In the selection, production and preparation of food, precautions should be taken to avoid chemical, physical and microbial contamination to ensure that food is safe for the animals and their young. All food hoppers and utensils should be cleaned regularly and sterilised when necessary. All fruit and vegetable supplements should be appropriately washed prior to presentation to the animals.
- It is recommended that feeding of young or handicapped animals (for example, those post-surgery or with muscular dystrophy) be facilitated by provision of food in a Petrie dish or hand-feeding as necessary.
- When moist food is used, it should be replaced regularly to ensure palatability and food safety.
- The animal house manager or a laboratory animal veterinarian should be consulted prior to supplementation or manipulation of complete commercial diets.
- Consideration should be given to the rotation of use and storage of formulated diets such that they are used within the recommendations of the manufacturer (particularly formulated diets supplemented with Vitamin C).
- Food used in microbe-controlled environments is often autoclaved to avoid the introduction of food-borne pathogens. As autoclaving decreases the concentrations of some vitamins and antioxidants, diets should be based on formulations that contain higher concentrations of heat-labile ingredients.
- Where animals are held in groups, care should be taken to ensure that subordinate animals have sufficient access to food and water. It is recommended that more than one access point for food (and water) be provided to reduce the possibility of aggressive competition.
- Any significant changes in food intake should be investigated.
Species specific recommendations:
- Consideration should be given to the presentation of food for certain animals that have abnormalities of the teeth and jaw.
- Taking into consideration autoclaving or irradiation requirements, Vitamin C can be supplied in the pelleted ration (800mg/kg finished diet) or supplemented in the drinking water (1g/litre), prepared fresh daily. Fresh vegetables can also be used to provide Vitamin C and should be thoroughly washed prior to presentation.
- Guinea pigs have a high dietary fibre requirement (16%), which is best met by supplying them with good quality lucerne hay. They should be provided with a diet of 20% minimal protein.
- The feed should be appropriately stored to maintain active levels of Vitamin C. As a guide, one half of the Vitamin C may be lost 90 days after the diet has been commercially mixed and stored above 22ºC.
- Guinea pigs are susceptible to anorexia following experimental procedures and may require special attention to resume eating. The use of a pellet mash mixed with water and hand fed to guinea pigs will often be sufficient for normal appetite to be resumed. A faecal pellet can be included to restore microbiological activity in the digestive tract after periods of anorexia.
- Consideration should be given to the type or placement of the feed hopper outside the cage to control wastage of food and contamination of the feed with faeces.
- It is recommended that foods such as hay, fruits, vegetables, legumes or green feeds be fed to supplement commercial pellets and to reduce the monotony of a fixed ration diet.
- A high fibre diet should be provided to help prevent diarrhoea and hairballs. A diet with between 18-25% fibre is recommended.
- If a restricted diet is required to be fed to rabbits, it should be provided at routine times.
Minimum standards for water provisions:
- Potable water must be available to all animals at all times.
- Precautions must be taken to avoid flooding in solid-bottomed cages.
- If Vitamin C is to be provided at effective levels in the water for guinea pigs, a non-copper delivery system and daily preparation of the water must be used.
- The source and method of water supply should minimise microbial and chemical contamination.
- Under certain conditions of transport, water should be provided in the form of a moist diet (see Section 3.8).
- Water bottles or containers should be sanitised or sterilised. They should be sufficiently transparent to enable water availability to be easily checked and have a wide mouth to facilitate cleaning. Water bottles or containers should always be replaced with clean, freshly filled ones and should not be able to easily tip or spill.
- Automatic watering systems should be serviced and cleaned regularly to avoid malfunction and the risk of spread of infection, drowning or drought. This should include checking for the correct pressure in the drinking valves to prevent back-flow of water into the lines when animals drink from, or play with, the valve. The nipples should be located at a suitable height to enable access for all animals. Some animals need to be taught to use automatic watering devices.
- These species are very susceptible to water deprivation. Water supply should be checked daily and if a problem is confined to one cage or box, blockage of a watering nipple or bottle should be considered as a cause in the first instance.
Species specific recommendations:
- These animals often waste water by playing with the sipper and therefore automatic watering systems are often not used. The sipper tube should be located outside the cage to prevent excessive wetting. If automatic watering devices are used, some animals require training.
- Open watering systems should be avoided to prevent infection of the dewlap.