AQHA January / February Magazine AQHA JAN-FEB 2020 PRINT | Page 22

PG.20
rapid ie from 4 months before until 12 months after
birth.
The time course for hock and stifle OCD is different.
Most hock lesions are generally present at 1 month
of age and there is evidence they can develop during
gestation, so correct feeding of the mare should
be practised before and after birth. Stifle lesions
appear between 3 and 5 months of age and there is
a positive correlation between OC and weight gain
in the 3rd to 5th months. The significance of this
is that correct, sound bone growth (ie we are not
focussing on muscle and cover at this age) must be
the priority for the weanling.
There is a link between above average weight gains
and onset of bone diseases. Muscle growth should
not be pushed forward while the bones and joints
are vulnerable. Excessive loading (usually due to
excess body condition), an unbalanced diet or hard
exercise affect the pattern of bone growth. Swelling
and lameness of the stifles and hocks are more
common in this age group. For growth to proceed
in a balanced and synchronised way, any sign of
lameness, filling in the legs or joints (including
bone and bog spavins) or abnormal limb angles
necessitates a cessation of exercise, a reduction in
the energy in the diet and a veterinary examination.
A lighter, leaner weanling with appropriate height
(remember height is an indication of bone growth)
is the ideal.
Whether weanling bone and muscle growth are
optimised is also influenced by the quality and
quantity of protein in the diet. Weanlings that don’t
have their needs met in terms of their protein -
more specifically, their amino acid - requirements
are shorter and fatter than those that do. Proteins
are made of chains of amino acids – good quality
protein is high in essential amino acids. In weanlings
it is lysine and threonine that are most often
deficient. Because every tissue (bone, muscle, red
cells etc) has its own ‘recipe’ of amino acids, the
number of new cells the body can build depends on
the right ingredients being available.
Amino acids that can’t be used because of
deficiencies of other amino acids are converted
to fat – and that’s not what we’re after at this age.
The percent protein on the feed tag is of little
use in terms of knowing whether it will meet the
weanlings requirements, because horses don’t
need a % protein, they need a number of grams of
protein each day. For example, a horse fed 3kg of a
10% protein feed, or 1½ kg of a 20% protein feed
gets 300g of protein in both cases. So % protein is
not useful in terms of knowing how much usable
protein the diet provides. Soy and lucerne are
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