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Lazy Thyroids, foundering, and foals...

Overweight Horses May be Due to Lazy Thyroid
(also foundering, farriers, and foals)

A few quick notes before we lay the topic of grass founder to rest.  The middle age gelding and non-producing mare that persists in staying heavy may have a medical reason for not losing weight.  It is not uncommon for these horses to have an inactive thyroid which can be confirmed with a blood test.  Without a functioning thyroid, the body’s machinery slows and burns fewer calories in the day’s activities.  As the horse gains weight, it will move even more slowly, which saves additional calories.

If the thyroid gland is underproducing, Dobbin can be supplemented through the feed.  With the metabolism stimulated, he will move faster and burn more calories.  With increased activity he will lose weight, feel better, and move about more willingly.  The weight loss will be slow but progressive and certainly in the right direction.

Another way to take weight off the mare is by breeding her.  This will have little effect while she is pregnant, but the nursing foal will draw her down like a deflating balloon!  The production of milk draws fat from the mare.

After the foal is eight weeks old we should evaluate the mare’s condition.  If she still needs to lose weight, reduce her grain.  This will of course lower her milk production a little, but by this time Junior will be eating with her and may have a creep feeder of its own.  Reevaluate the mare’s condition again in a month.  The weight tapes work well for this.  If more weight loss is needed, we suggest taking the grain away completely.

We evaluate a horse’s condition by feeling the rib cage with the flat palm of our hand .  Ideally we should feel the ribs under a thin cushion of fat.  If we cannot feel ribs with our flat palm, a great deal of weight needs to be lost.  If the ribs feel hard to the hand, the mare is too thin.  The mare that was fat will regain weight quickly after the foal is weaned, so she can be reduced to below optimal condition without concern.  In addition to producing another horse for the herd (and another patient for us), allowing the foal to nurse the mare down will delay for months or years the need to dry lot her for protection from founder.  This is, of course, if we can resist the temptation to feed her when we see she is losing weight.

If we have to eliminate the mare’s grain in the later stages of nursing, the reduced milk flow will make it easier to wean her foal. The mare’s milk production peaked at six to eight weeks, then it started declining, but the foal’s needs continued to increase.  By weaning, which can be as early as three months if the foal weighs 300 pounds, the foal is nursing for the pleasure of it more than any nutritional benefit.

Unfortunately,  if the mare is affected with an underactive thyroid, she will have difficulty becoming pregnant.  The thyroid situation will need to be evaluated, and if necessary corrected, before there will be sufficient circulation through the uterus to nourish an embryo.

Now, back to foundering.  As the farrier works with the feet of the horse that is recovering from grass founder, it will be necessary to remove a great deal of the front of the hoof.  If there has been separation of the coffin bone from the hoof, the area will have filled with blood.  The first time we see this area opened it can be a real shock.  It is not a pretty sight but a necessary one.  Only after the front of the hoof is opened, and the area allowed to dry, will the health of the foot improve.  It will also shorten the toe, in order that  the new hoof wall can grow down in contact with the coffin bone inside.  Until then, the hoof wall will grow straight down from the hair line for a short distance and then start angling away.  We can visualize the coffin bone within the hoof with a side profile and the hoof can be shaped to the bone.   X-rays of the foot are a big help.  By looking at the X-ray, the farrier can remove the excess toe, and possibly lower the heel.  If you have a horse recovering from founder, do not be surprised when the farrier opens a dark cavity in the front of the hoof; they are trimming the excess wall.  Opening it will allow drying, but it’s significance is an indication of the separation that occurred some months ago.  With the hoof growing at 1/4 to ½ inch per month, it may take a few months for the cavity to grow out.

Next week we will return to one of our favorite topics, reproduction.  Reproduction and spring are inseparable for the horse.

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