Supplying Minerals - A Question of Source?

Minerals comprise less than 0.7% of the body, but their dramatic effects on a variety of animal functions make minerals and their balance absolutely essential for proper nutrition.

Essential minerals in animal diets are composed chiefly of the macro minerals calcium, phosphorus, potassium, sodium and magnesium (measured in parts per hundred), but include micro minerals iron, zinc, copper, manganese, iodine, cobalt and selenium (measured in parts per million).

Macro minerals are involved in structural integrity, acid-base balance, osmotic pressure and cell, nerve and muscle function. Most micro minerals are components of metallo-enzymes while iodine is necessary for thyroid hormone, iron for hemoglobin and cobalt for vitamin B12 synthesis.

Indiscriminate supplementation of minerals is likely to be more harmful than beneficial with mineral imbalance the most likely cause of several problems in dogs, cats and horses.

In the last ten years, a renewed interest in the bio-availability (availability of the mineral at the target tissue) of mineral source has helped drive new generations of organic minerals. Comparatively little information exists on the bio-availability of minerals for pets and horses but research continues on optimum inclusion levels in the diet to maximize the health and "well-being" of the animal (e.g. dogs and horses with a predisposition to joint disease).

Problems with classical mineral deficiency in pets are now seldom seen when feeding commercial diets (but still occur with home-mixed diets) and more likely relate to mineral interactions or bio-availability problems. Minerals in animal diets are unique nutrients because they contain no carbon, which makes them inorganic molecules.

A new class of minerals, called chelated or organic minerals, is now available to the animal feeding industry. Organic (or chelated) minerals differ from inorganic minerals in that the mineral element is bound to amino acids or small peptides to form a structure that is stable and electrically neutral. This differs from traditional mineral form where the mineral element is bound to another inorganic mineral such as the typical oxide or sulfate inorganic (rock) mineral form of manganese oxide or ferrous sulfate.

Studies on the digestion of organic minerals indicate that organic minerals are viewed by the body as protein rather than mineral during their absorption from the intestinal tract. The stable protein structure can increase the mineral's absorption across the gut wall and can hide the mineral element from other minerals that might interfere with absorption. For example, chelation can shield a mineral from external influences like unabsorbed calcium binding to zinc reducing its availability.

There are many naturally occurring organic minerals including chlorophyll (chelated magnesium), vitamin B12 (chelated cobalt) and hemoglobin (chelated iron) and so this relatively new concept is not an unusual mineral form to the animal.

Organic minerals must be used in conjunction with inorganic mineral forms to assure mineral requirements will be met. The relative amounts of different mineral sources is an important question to commercial nutritionist as a determination of relative bio-availability may be more important than the absolute amount of a particular mineral in the diet.

Inorganic oxide mineral sources have been popular in the feed industry because of their low reactivity with other minerals and minimal water reactivity or crystallization. It is well known that the oxide form of minerals such as copper oxide and iron oxide have poor availability in animals. Other oxide forms have reasonable absorption and bio-availability. Sulfate forms are popular but reactivity may be high due to crystallization with water. Studies with chelated zinc have shown advantages in terms of availability, animal performance, and reductions in mineral inter-action.

Qualified nutritionists use this data to design improved diets considering the potential health and animal welfare benefits of appropriate mineral levels at target tissues. Diet mineral levels should always be based on sound ingredient analysis. If a qualified nutritionist has designed a diet, do not supplement with additives unless directed by a veterinarian or nutritionist. Additional supplementation with vitamins and minerals is not necessary and may cause mineral imbalances.

David Dyble, M.Sc.,P.Ag. Nutritionist, Agro Pacific Industries