Back to Basics - Dietary Supplements: Can they be too much of a good thing?

Until relatively recently, most advice concerning ferret nutrition has been focused on avoiding an inadequate diet, and quite rightly, too, considering the ‘feed ‘em bread and milk’ mentality that has often persisted.

However, with the advent of many good proprietary complete ferret diets, and the variety of vitamin and mineral supplements now available on the market, there perhaps needs to be a cautionary reminder that dietary problems can also result from the over-provision of various vitamins and minerals.

‘Complete’ ferret diets are just that – they contain all the nutritional requirements that most ferrets need. Fresh meat diets, on the other hand, may need some supplementing in the form of vitamins and minerals to attain the equivalent nutrition. The question of what you give, in what amounts and in what combination, is important since it can lead to health problems.

Dietary supplements certainly have their place for pregnant and nursing jills, for sick or convalescing ferrets, and when veterinary advice prescribes the need for them. However, an excess of supplements, or a prolonged combination of complete diet and supplements, can interfere with nutritional balance. Unfortunately, many pet owners (and this isn’t confined to ferret owners) are tempted to give excessive amounts ‘just to be sure’ their ferrets get enough or to promote growth in kits. The effects can be as bad as giving a deficient diet. Whilst some vitamins such as the Vitamin B group are water soluble, which means that any excess is excreted with no more damage than giving you an expensive pile of poo in the litter corner, other vitamins can be stored in the body and can be toxic in excess.

Vitamin A, present in high levels in both complete foods and many vitamin supplements for improving skin and coat condition, is not excreted but is stored in the liver. In mammals, an excess is known to give rise to forms of cirrhosis, bone pain, bone malformation and anorexia. In America, some vets have suggested a link between too liberal a usage of vitamin supplements and liver damage, lameness and poor appetite in adult ferrets, and bone problems in younger ferrets. This has prompted a recommendation that vitamin supplements not prescribed by vets should be diluted with olive oil if intended to be used fairly regularly as treats. Indeed, for our own ferrets (who adore Ferretone but are fed on a mainly complete ferret diet) we dilute their treat by sprinkling it on a tablespoonful of water. We find this also encourages the ferrets to drink the water to the last drop. (Those of you who know me will be aware that I have a major concern about whether ferrets on complete diets drink enough water, especially from water bottles rather than bowls. My feeling is that many ferrets are lazy drinkers and need encouraging to take more fluids - but that’s another soap box of mine!)

Vitamin D, necessary to maintain calcium and phosphorous levels for bone growth, may also be unwittingly over-provided through proprietary supplements or cod liver oil. Symptoms of excess may be anorexia and calcification of soft tissues, resulting in damage to joints, pain and lameness.

Mineral supplements, proprietary or otherwise, should also be used with caution if an otherwise complete diet is fed. The principal dangers are excess intake of calcium and phosphorous. Bones and bonemeal are essential to bone growth and form the basis of many mineral supplements. However, too much in a diet can result in high levels of bone deformity. Rickets, usually associated with a calcium deficiency, can also be due to an excess of phosphorous in the diet, whilst excess of calcium can produce severe abnormalities in bone growth in young animals and deformities in older animals.

Other minerals known to be harmful in excess are iron (producing weight loss and lethargy); copper (anaemia and occasional hepatitis); and iodine, which affects the thyroid gland. Strangely, the symptoms of excess iodine can be similar to those of iodine deficiency, being hair loss and lethargy.

Although these dietary problems are well documented in other mammals, little has yet been collated regarding their effects in ferrets, probably due to the fact that up to now ferret diets have tended toward the inadequate rather than the over-adequate. However, the dangers are real and are all the more sad because they are most likely to affect owners who genuinely care for their ferrets and want to do the best for them. Equally disturbing is whether such problems would be readily recognised by vets. Although there are many more vets now who take interest in ferrets, there is still a real possibility that dietary imbalances are not readily detected. It is also possible that a ferret thought to be sick may well be given extra supplements!

It would be wrong to dissuade anyone from using a complete ferret diet and/or supplements. Indeed, they are to be welcomed for the sake of most ferrets. But caution is needed to guard against unnecessary use of supplements in an already balanced diet unless there is clear veterinary need. I have seen so many distressing cases in other animals that have resulted in permanent damage. I would never wish to see these problems arise in ferrets. Perhaps the bottom line is that the price we pay for the nutritional value and convenience of these ferret products is our vigilance in how and when we use them.

PS. A final word on treats. Many ferrets have tastes that belie their ‘obligate carnivore’ status. Ice cream, chocolate and all manner of fruit and vegetables seem to attract ferrets. Indeed, the cover photo on this issue shows a ferret tucking into a chunk of cucumber. Ferrets (like us!) do get a taste for the things that aren’t necessarily good for them. It is best to keep such treats to a minimum, if given at all. Cucumber is, perhaps, one of the least worrying as it is mostly water. Even so, it is not really suitable except for occasional treats. I bet ferrets will hate me for saying that! My potato/mushroom addict will probably not speak to me for weeks now.

(From Ferrets First Issue no. 25e September 2005)

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