Ridecamp: Re: [RC] Pasture

Let me ask a question here--when you took your mare off pasture, what did
type of hay did you put her on?  The reason I ask is that fescue hay is also
toxic.  The problem isn't limited to the fresh fescue.  The toxins are very
stable over time, so if they were getting any fescue hay at all, it defeated
the purpose of removing them from the pasture.

The toxins themselves are cleared from the mare's system very rapidly--we
know this because there is a significant increase in serum prolactin within
twenty-four hours after you remove the endophyte from the diet. However, the
effects on the steroid hormones take longer to reverse.  If she was removed
100 days out, there should have been milk production without much problem,
unless she was just predisposed to being a poor milker--unless she was still
getting some of the toxins in her diet in some fashion.    We know that it
takes very little of the toxin to cause a problem---as Claudia pointed out,
her pasture was only 50% fescue.  We started seeing problems in the
experiment station pastures that were becoming reinfested due to moving
stock from infested pastures (seed is the only way the endophyte is
transmitted).  Made life difficult for me on the last study, some were so
badly reinfested--one was up to 40%.

Having said all that--there's no question that there are residual effects,
and in some cases I wouldn't expect complete perfection even at 100 days
out, simply because it takes a while for the steroid hormones to readjust,
and with plain withdrawal it takes longer than if they are being treated
with Equidone.

Withdrawal isn't a cure-all...however, it does achieve the main goal which
is to save lives.  I saw the train wrecks that occurred when animals weren't
withdrawn at all--the high mare and foal mortality, the suffering, the
broken calving jacks, etc.  Trust me--the problems associated with
withdrawal seem minor in comparison.  One very significant problem we see in
mares that aren't treated or withdrawn is that the foals do not rotate into
the proper position for delivery--they are usually 90 degrees out of plane,
i.e., their spines are aligned with the mares' side instead of with their
spines.  The mare's pelvis just isn't designed for that, and the number of
foals that get stuck is appalling.  I saw some horrific results, trust me.

The fact that withdrawal alone isn't perfect, and the fact that not everyone
who breeds horses in the fescue belt has the facilities or labor or money to
keep mares off fescue for the majority of the pregnancy is why we searched
so hard for the drug.  Now, if the FDA would get off it's collective butt
and finish approving it...sigh....

Lisa


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