Re: Selenium

[CMKSAGEHIL@aol.com]

Hi, Tracy--

YES, your mare should be tested for selenium.  Most of my practice is equine
reproduction, and selenium deficiency is one of the biggest problems I see in
my area.  We see lots of mares that appear to be absolutely normal that simply
will not settle, but will breed just fine once their deficiencies are
corrected.  Other problems we see in deficient mares are windswept foals,
contracted tendons in foals, and retained placentas.  White muscle is
relatively rare in horses, unless the deficiency is extreme; it does
occasionally occur, though.

The vet in your area may be right on regarding the idea that the selenium
deficiency makes the mares prone to infection.  Although there is not much
research to back this up, many doctors with better research minds than mine
feel that the uterine immunity is sufficiently impaired by the deficiency to
not allow the uterus to clear the contamination of breeding in time for the
embryo to survive, but that it clears prior to the next cycle, so that the
mare will appear to be "clean" on culture.  When a mare is bred, there is
"contamination" in the uterus--this may or may not include bacteria (it does
in natural breeding), but even semen and/or semen extender is a foreign
substance and causes an inflamatory response in the uterus.  White blood cells
respond and "clean up" the resultant mess to return the uterus back to its
normal state.  The fertilized egg spends 5 days in the oviduct before coming
down into the uterus.  If the contamination of breeding has been successfully
cleared by that point, the uterus should be a friendly environment.  However,
if there is any delay in this clean-up process, the fertilized egg descends
into a microscopic war zone and is quickly dispatched and resorbed with the
rest of the debris there.  Since selenium is important for the proper function
of cell membranes, the white cells trying to clear the debris of breeding
don't function properly in the deficient mare, and the clean-up process is
delayed.  Likely the cells lining the uterus don't function properly, either.

Hope this explains the process somewhat...

Heidi Smith, DVM--Sagehill Arabians (Oregon)