Eleanor Kellon, VMD
Just to add to Kathleen's excellent answer, to put the sampling
procedures in perspective for you, they don't come out of the blue.
They are based on studies that used much larger numbers of samples
looking to determine the best way to sample "lots" of hay of X size
to get results that are truly representative. If you see obvious
variability in the bales (e.g. you might get a shipment that is
actually from multiple cuttings and you can see the bales look
different), sample so that you also reflect that.
For example, if you notice that 25% of your bales look more weathered
or have more seed heads, etc. when you do your cores sample to
include 25% cores from those bales in the total - in your case, 5
cores from those bales.
Yes, they are called trace for a reason but the relatively small
requirement does notin any way mean insignificant roles for these
minerals. The lecture on trace minerals in my nutrition course is 25
pages long and it barely scrapes the surface! They are critically
important to enzyme systems, hormones, the immune system and cellular
defenses (antioxidants). "Biologically important" doesn't do them
justice. Absolute deficiency means death. Less dramatic inadequacies
mean health is compromised. You probably did at least one high school
chemistry lab where adding just a "speck" of something produced a
dramatic reaction (teachers love those!). The interior of your
horse's body is a chemical soup too.
One reason we supplement is to guarantee adequate daily intake of
individual minerals. The amounts you are adding actually correspond
to at or just over the minimum daily requirement for those two
minerals. The other reason, like Kathleen said, is to keep balance.
Some minerals serve to balance out reactions produced by other ones
(e.g. copper and zinc in superoxide enzyme systems protect from
oxidation from free iron ion reactions with oxygen), others work hand
in hand to make things happen, like copper and zinc ions in hair
pigment producing systems.
No, we can't get 100% precise, but the horse's body has it's own
compensatory mechanisms to increasing absorption a bit, storing for a
rainy day, excreting excesses (except iron). What it can't do is
create a mineral out of thin air so we're trying to A. avoid overt
deficiencies and B. make the job of keeping everything in balance
easier so that cellular functions run smoothly.
More is never better because it just sets to stage to upset balance
again. That doesn't mean you have to be obsessive about every mg, but
there's a reason behind the recommendations. One list member
commented to me yesterday that she was comparing photos of her horse
from recently and a year or so ago and noticed how much less grey
hair the mare has. Another person I'm working with has had a
warehouse of different supplements thrown at it and now the hair is
falling out and her immune system is in an uproar.
The effects of trace mineral balancing are mostly on the inside.
Because they are geared at health maintenance, they may not be
immediately obvious. Where you will see them showing up is things
like better muscle/joint/tendon function and strength, fewer problems
with infections or allergies (we have FAR fewer problems with things
like that on this list than say the Cushing's population in general)
and incredibly robust foals.
If you see an obvious problem with minerals sifting through your
meals, a better solution is to wet it slightly, or mist with oil,
before mixing them in.