All mammalian diet is made up of certain constituents, which are needed by different species in varying amounts. Roughly broken down these are protein, fat, carbohydrate, fibre, vitamins and mineral.
Protein is required for the health, growth and repair of body cells and structures (for example muscle, bone, nerves and blood).
ii. Adult rats
Adult rats, other than those who are pregnant or lactating, require a diet with approximately 10%-15% protein. Younger adult rats seem fairly tolerant of slightly higher levels of protein. Protein is made up of amino acids, which cannot be stored in the body – any excess is broken down and detoxified in the liver, and then excreted by the kidneys. Over time many rats develop nephritis and degrees of kidney failure (which male rats seem particularly susceptible to). Once the kidneys begin to fail high levels of proteins and less digestible proteins will speed up the process. Studies have shown that long-term diets of around 20% protein increase the occurrence of kidney lesions in elderly rats. However, too little protein (probably less than around 8% of an adult rat’s diet) or a completely vegetarian diet may lead to a deficiency in the essential amino acids, which are so necessary for the health and repair of body tissues.
iii. Growth and lactation
Lactating and rapidly growing rats (up to about 3-4 months of age) require higher levels of protein (20-25% of their diet) to support milk production and growth.
iv. Not all proteins are equal
Not all proteins are equally easy for the body to break down and the processing of some will produce more stress on the liver and kidneys than others. Eggs and milk proteins are easiest to digest followed by soya, fish and chicken, then red meats and finally other plant sources like corn, nuts and wheat. This information is particularly important when choosing dietary protein for older rats, whose kidneys may be beginning to degenerate.
v. Vegetarian rats
Rats are omnivores and thrive on diets that include some animal protein. A completely vegetarian diet will support a non-growing rat, but (unlike humans) has been shown to be insufficient to fully support the needs of pregnancy and lactation. This is due to the extremely rapid growth of rat kittens in the first few weeks of life.
Fat is a useful high-energy source and also contains nutritional factors essential for health.
ii. Adult rats
A healthy rat diet is very low in fat, around 4-5%. It has been demonstrated that the incidence of mammary tumours in rats increases substantially with diets high in total and saturated animal fats. High levels of fat in the diet may also lead to itchiness, skin lesions, hair loss and obesity, which increases the risk of strokes, diabetes and other illnesses.
iii. Growth and lactation
Rat milk is composed of 3.5 percent carbohydrate, 20 percent fat and 10 protein, and this level of fat is needed to support their early rapid growth (with 60% of energy requirements being met by fat). The level of fat required then decreases significantly as growth slows down.
iv. Not all fats are equal
Essential fatty acids can be split into two groups: Omega 3 and Omega 6. Sources seem to suggest that both of these are required in the rat’s diet. Omega 3 fatty acids have a particularly beneficial effect on cardiovascular health. It seems to be generally accepted that it is necessary, for optimum health, to encourage the intake of Omega 3 fatty acids at the expense of some Omega 6 sources.
Good dietary sources:
- Omega 3 – walnuts, oily fish, soya, flax seed/oil, coconut.
- Omega 6 – vegetable oils, animal fats.
These are the high energy, low/non fat foods such as grain, fruit and root vegetables.
ii. Adult rats
These should make up the bulk of an adult rat's diet (approximately 80%). They supply the body with energy for everyday activity, growth and reproduction. If fed in excess they will be turned in the body to fat.
iii. Growing and lactating rats
During this phase of life carbohydrate intake should be reduced to make way for increased protein and fat intake.
iv. Longevity and energy restriction
A number of studies have shown that by moderately restricting energy intake (while making sure that nutritional requirements are met) in comparison to the energy intake of rats that are fed ad libitum (food freely available at all times) can significantly increase lifespan, and reduce the incidence of age related illness. I would recommend that from 3-4 months all rats have a lean period of 4-6 hours each 24 hours – a time when food is not available in any quantity. To achieve this only feed the volume of food that your rats will eat in a 18-20 period. This lean period should not be while they are sleeping… making it best to feed (once a day) later in the evening once your rats have already been awake for a few hours. Fast days, half rations and giving no food before or after a clean out are all alternative ways to reduce food intake.
A rat's need for indigestible fibre is well supplied by the whole grain element of their diet. However, when feeding pasta, rice, cereal and bread it is best to choose unrefined 'brown' or whole grain varieties, as these are rich in vitamins and minerals that are generally removed by processing. Fibre has benefits in maintaining wieght and a healthy digestive system, but it also reduces the absorption of essential minerals and other nutrients.
ii. When fibre is useful
A higher fibre diet free from refined carbohydrate is useful in supporting rats with diabetes mellitus.
Rats do not seem to suffer greatly from vitamin deficiencies, though potentially they can. Almost all lab blocks, generic mixes and human cereals have vitamins added to them. Feeding a small amount of fresh fruit and vegetables everyday can also serve to boost vitamins in the diet. Rats, unlike humans, are able to make and store their own vitamin C, so do not rely on a regular daily intake.
ii. Supplementing vitamins
With a varied diet of good quality based on a commercial mix it is not generally necessary to supplement vitamins as these are already added to the food at source. However, if you choose to feed a straight grain based mix then supplementation is essential to add in what a feed manufacturer would do for you, and to prevent deficiencies in your rats.All sick, elderly, growing and lactating rats will benefit from vitamin supplements, however, some people are re-assured by giving a multivitamin/mineral supplement once or twice a week throughout life. Dr Squiggles make two – one that is a dry powder that can be sprinkled onto fresh food (Essentials Plus/Tiny Animals Essentials) and a second that is a soluble powder that can be added to drinking water (Daily Essentials).
These are trace elements that are essential to health. They are added to lab blocks, EMP (egg based hand rearing food for birds) and generic mixes to varying degrees. One or two are worthy of special mention. Magnesium has been found to have a protective effect against the formation of calcium crystals in the rats kidneys (female rats are susceptible) which lead to blockages, pain and kidney disease.
Copper deficiency can lead to many problems and can be diagnosed by loss of hair pigmentation around the eyes (pale rings). Young rats have a higher requirement for copper (up to about 4-6 months). Requirements for rats seem to be around 15mg/kg of food.
Calcium and phosphorus are essential, and needed in increased quantities during times of growth, pregnancy and lactation for the laying down of bone and production of milk. One of the best (balanced and most readily accessible) sources of these minerals in the diet is curly kale. If unavailable this can be substituted with other green leafy veg (such as spring greens, pak choi, broccoli).
ii. Supplementing minerals
Beyond the multi mineral supplements already mentioned there are two minerals that rats might regularly benefit from receiving:
- Copper - making homemade mixes can sometimes result in low copper diets.
- Calcium – lactating and growing rats may benefit from calcium supplementation. Dr Squiggles have a suitable liquid product called Calcivet that can be added to food or water, Calicvet can also be bought in powder form for adding to food. Calciform is another liquid product that provides vitamin D and calcium, but not magnesium where Calcivet does.
Foods with special properties
Some foods have some antibiotic properties such as bananas, plums, prunes, garlic, courgettes and raspberries, while others have some anti-viral properties such as cranberries, strawberries, plums and prunes. These foods should never be used as a substitute for proper medical care.
ii. Anti arthritic properties
Fish oils, dates, ginger and garlic may help rats with arthritis.
iii. Anti cancer properties
Broccoli and red grapes are thought to have protective effects against cancer, while regular soya in the rats diet has been shown to reduce the rate of mammary tumour occurrence significantly.
iv. Broncodilating properties
Very dark chocolate is a mild broncodilator (dilates the airways when breathing is difficult) and can be used in small quantities for rats with respiratory illness, in an emergency.
v. Immune system boosters
Many foods have a positive impact on the immune system, strengthening a rat’s natural defences. Some of these are brown rice, oily fish, carrot, almonds, broccoli, garlic (raw), strawberries (and other berries), flax oil, fish oil.
Author: Alison Campbell