sources of vitamins and minerals in pet food.
question has been asked 'Why do Burns add vitamins and minerals
to the food and not rely entirely upon natural sources of
these nutrients - i.e. through the use of seaweed?'
Although Burns do include seaweed as a natural
source of nutrients we also add vitamins and minerals to the
food to ensure that the food contains consistent amounts of
these nutrients to meet the nutritional requirements of your
pet and ensure that over or under-nutrition does not occur.
Natural forms of vitamins and minerals are
very unstable and consistency can never be guaranteed, this
can cause large variations in nutritional levels. These large
fluctuations can be detrimental to the quality of the food.
The natural forms also have an unknown bio-availability and
therefore specific levels cannot be guaranteed; they are also
associated with undesirable substances for example heavy metals,
which would be detrimental to the pet. The variability is
too inconsistent for us to confidently use natural forms of
vitamins and minerals.
The NRC (National Research Council) and AAFCO
(Association of American Feed Control Officials) publish recommendations
for the minimum levels of 17 vitamins and trace minerals that
should be present in nutritionally complete pet foods. These
figures are based upon deficiency and toxicity cases presented
to vets, and some feeding trials. Natural ingredients, by
definition, are very unlikely to contain consistent quantities
of these nutrients (e.g. due to seasons, weather, soil type,
etc) therefore, supplementation with exact quantities is necessary
in order to avoid chronic deficiencies or toxicities.
Whilst it could be possible to reach the minimum
levels necessary (using natural vitamins), the balance between
nutrients is very important. For example, seaweed can contain
high levels of magnesium which interferes with the uptake
of zinc and copper from the diet. Also, in order to meet the
minimum levels of less prevalent nutrients such selenium;
you would need to add high quantities of seaweed, which could
in turn lead to toxic levels of other nutrients, such as iodine.
Many vitamins found in nature do not survive
the cooking process. For example, the natural form of vitamin
E is delta-tocopherol but this is virtually destroyed with
mild processing temperatures. We add alpha-tocopherol, which
survives very well and is absorbed efficiently from the gut.