The skin, coat and body condition of a rat can tell you a great deal about its overall health, well-being and nutritional status. Condition (in the rat) may be defined as:
- Having good muscle tone and moderate weight for build; neither skinny nor overweight.
- Being bright and alert, with abundant energy and vitality.
- Having a short, smooth and glossy coat (except for rex, hairless etc).
- Showing clear skin, free from dryness, flakiness or sores. Some orange buck grease at skin level is normal for males.
- Having bright, shiny eyes.
The skin is the largest organ in the body and its demands on metabolism are huge. It is thought that about a quarter of all protein intake is used to regenerate hair and skin, and to produce secretions from the skin’s many glands. Fats, vitamins and minerals are also required for this, therefore, the skin and hair are good indicators of the quality of nutrition. A variety of skin conditions (for instance, dandruff, irritation, lesions and poor healing) and many problems with the coat (including thinning, patchiness, dryness, very long hair, a greasy feel, faded and patchy colouring or dullness) can all be the result of inadequate diet and lack - or excess - of nutrients. These signs can occur in isolation, or a number of issues might arise at the same time.
The biology of the skin and hair
Hair (fur) is an anatomical feature that is unique to mammals and has a variety of functions, such as insulation, waterproofing, improving the sense of touch, display (e.g. increasing physical ‘size’) and colour patterning (e.g. camouflage).
Hair grows out of follicles in the lower layer of the skin (dermis) and each follicle normally grows one hair. The part of the hair below the surface is called the root, while the part that is seen above the skin is the shaft. The activity of the hair follicle is cyclical and each period of activity and growth is followed by a resting period. After the resting period, a new cycle begins and a new hair is formed, which pushes the old hair out from below and the hair is shed (moulting).
The length of a hair is determined by both the length of the resting phase and how long the active growing period lasts. These vary from species to species and, within an individual, may vary between different types of hair and this explains why humans can have notably longer hair on their heads than on their arms. Despite the differences in hair length not being as striking in rats, there is some regional variation, with shorter hairs on the head and belly in comparison to the rump. The hairs covering the chest and abdomen of the rat have a resting period of about two weeks and a growing period that lasts roughly as long, whereas in the centre of the back the resting period is about four weeks and the growing period lasts for three. This accounts for the spine and rump always being the last area to moult out, and also for the fact that hair in this region shows lack of condition more dramatically than other areas; put simply, the hair there is older.
In most animals the cycles are synchronised to some degree so that the hairs are all due to be shed at around the same time (a moult). If the cycles are not synchronised then hair is lost continually, but never in large amounts; this is the pattern that is seen in humans.
In the rat, the active growing period for each hair is approximately two to three weeks and the resting period, two to four weeks and cycles do occur at roughly the same time, but in a pattern of progression across the body. This means that rats moult out fully approximately every six to seven weeks, and the moult always begins at the belly, progresses up the sides of the body to the spine and moves from the back of the neck towards the tail. This can lead to some very bizarre coat ‘patterns’ as the new hairs replace the old. Interestingly, in female rats the growth cycle is slower than in males, and the length of the hair in all regions is shorter.
There are a number of factors that are thought to affect the rate at which moults occur and the speed at which cycles of growth repeat. These include hormones, nutritional status, stress, disease and environmental factors such as heat (a warmer environment may shorten the cycle). These effects can be seen most notably in kittens who are stuck in moult; those who do not moult out into adult coats for unusually long periods of time. These kittens are generally ill, undernourished or experiencing stress. However, delayed moulting can occur throughout a rat’s life, which can lead to a coat that looks long and out of condition.
Poor coat quality and condition may indicate underlying illness, or even a hormone deficiency (such as hypothyroidism). It may also result from stress, for example, when a rat loses a cage mate or there are changes within group structure. The most likely cause, however, is also the easiest to rectify; inadequate nutrition.
Hair, though dead throughout the majority of its length, is composed mainly of protein. The active growth cycle involves rapid cell division, which depends on many micronutrients and hormones. The benefits of an excellent diet cannot be overstated, but at times when coat quality and condition are lost, extra supplements may also be of benefit (see below). One should remember that during the moult all coats will tend to look a little patchy and below peak condition. Excellent nutrition and lack of stress will help the rat to pass through this phase as quickly as possible, and this can be helpful for those who wish to exhibit their pets.
For a rat’s coat to look its best and gleam with health and condition, its overall diet needs to be adequate in protein (requirements vary with age) and essential fatty acids (EFA). EFA are needed in cell division by all animal cells, but the hairs are also ‘oiled’ by sebaceous glands, which secrete an oily substance (sebum). Too much oil in the diet isn’t helpful for many reasons, including the coat becoming greasy, but where dietary fat is low, a drop or two of fish oil, flaxseed oil or olive oil (or some seeds or oily fish) a few times a week will help to boost condition. Vitamins, particularly A, B2, B6, C and E, and minerals, such as zinc are essential for healthy skin, and healthy skin is essential for good hair growth. Thyroxin is a hormone which is required anywhere where rapid cell division occurs, as in the skin, and iodine is needed for the production of thyroxin.
Clearly the relationship between good nutrition and condition is crucial and cannot be ignored. The more varied and appropriate your diet is, the better condition your rats will be in. Good condition is fuelled by adequate protein, essential fatty acids, vitamins and minerals, so if your rats don’t seem to be gleaming, look at your diet for any possible gaps. If the quality seems good overall then try adding in some hemp and flax seeds and supplementing with a little extra fish oil, some seaweed and a multivitamin and mineral powder for a week or two. It might just be that the rats are experiencing an underlying stress (such as building noise, extreme weather, disruptions in cage hierarchy, your own stress or ill health) and just need some extra nutrients to boost them at a difficult time.
Part of healthy hair growth is pigmentation, and minerals such as iodine and copper will also improve colour. Hair colour has been shown to be changed by free radicals (highly reactive molecules that can cause damage within the body), exposure to sunlight and certain chemicals. Free radicals can be neutralised to some extent by giving antioxidants, (such as vitamin C and E), which occur naturally in many fruits and vegetables. As rats are most comfortable at low light levels, avoiding direct sunlight will generally be an integral part of their care.
In elderly rats the coat tends to thin and lose condition, which may in part be due to underlying disease processes, less efficient uptake of nutrients, increased cellular damage, and changes in the growth cycles of the hair. Many elderly males get softer, shorter coats particularly over their back as they age, probably due to hormonal changes. The prominence of guard hairs diminishes, which can lead to an apparent lightening of colour in ticked rats, and the shorter base fur can look wavy but these changes are unlikely to be a cause for dietary concern.
Useful supplements for coat condition
Seaweed powder or unsalted seaweed - contains iodine and many other trace minerals.
Omega-3 fatty acids - fish oil or linseed (flax) oil. Hemp seed seems to be particularly helpful in improving coat condition.
Dr Squiggles Tiny Animal Essentials (multivitamin and mineral powder) or Daily Essentials (multivitamin and mineral for use in the water).
Optimizing skin and coat condition in the dog - D. H. Lloyd PhD, B VetMed, FRCVS, DipECVD Royal Veterinary College, UK K. A. Marsh BSc, PhD WALTHAM Centre for Pet Nutrition, UK
British Medical Journal, 1965, 1, 609-614 - Endocrine Influences on Hair Growth - Arthur Rook M.D., F.R.C.P.
Journal of Endocrinology (1958) 16, 337-NP - Quantitative studies of hair growth in the albino rat - Elizabeth Johnson
Adapted with permission from The Scuttling Gourmet
Author: Alison Campbell