A pregnant mare has enough reason to be a bit sluggish, uncomfortable, and not move around much. By the time a mare is into her second and third trimester, the weight of the uterus and foal will begin to slow her down. You may not see her freely trotting and playing like she may have in the past. She also may be more subdued, even grumpy at times. All of this is normal. However, early or mild laminitis can cause these same nonspecific symptoms in pregnant mares, and it’s wise to be on the lookout for it.
If the mare is spending an unusual amount of time just standing still, is lying down more than she used to, or is standing in an unusual posture, check the feet for any increased warmth or elevated strength of the pulses. Even if you’re not sure about whether those things are abnormal or not, observe her moving around at the walk and trot and see if she shows any soreness when turning. If in doubt, get your vet out for a check and nerve blocks if need be. The sooner you detect the problem and get her the help she needs, the better the outcome will be.
No one can say for certain what causes the laminitis in a particular mare. Extra strain on the feet from the weight increase is certainly a physical factor. Letting the mare go too long between trims could also contribute to the problem.
We also know of several cases where blood work has demonstrated an elevated blood glucose and/or insulin. Pregnancy-induced glucose intolerance/diabetes is well described in people and may well be what is going on in these mares, too, a situation similar to grass founder and/or laminitis in overweight, cresty horses and ponies.
Juliana was an Arabian mare who had never had trouble with laminitis. About midway through her pregnancy she started showing an ill-defined foot soreness. When laminitis was suspected, her vet ran a BET Cushing’s panel that showed an elevated insulin and loss of the day-to-evening cortisol rhythm. On the basis of this, it was suggested to put her on cyproheptadine. However, it has been shown that cortisol rhythm is lost in pregnancy and the BET panel is estimated to give at least 35% false positives anyway.
The owner opted to try a dietary approach instead, using grass hay, beet pulp, rice bran and a mineral and amino-acid supplement. The mare did well. Insulins came down steadily, foot soreness improved. She gained weight and delivered a lovely, vigorous colt without problem.
Also see the insulin-resistance article in this issue and laminitis articles in February 2002 and June 2002.