Q: My mare is pregnant and due next March. Are there any supplements I need to avoid for her? I’ve heard that devil’s claw shouldn’t be fed to pregnant mares and this got me wondering if there are any others that I need to avoid.
A: When choosing a supplement for a pregnant mare, read the label carefully including the small print, and this should tell you if the product is suitable. The main ingredients that may be unsuitable for pregnant mares are herbs, since they have a variety of active constituents, many of which have not been tested on pregnant mares.
Herbs commonly fed to horses which should not be fed to pregnant mares either because they have unwanted effects like uterine stimulation, or because there is no data proving their safety, include Vitex agnus-castus, devil’s claw, burdock, coltsfoot, comfrey, ginkgo, ginseng, hawthorn, hops, liquorice, meadowsweet, lemon balm, milk thistle, nettle, passiflora, red clover, slippery elm, valerian, wormwood, rosemary and sage. Chamomile, Echinacea purpurea, fenugreek, garlic, ginger, marshmallow, and thyme can probably be fed in small quantities, without any adverse effects, based on human information.
Nutraceuticals including glucosamine, chondroitin, MSM, pre- and probiotics and feed materials including brewers yeast and linseed (flaxseed) oil should be safe for pregnant mares. Macro-minerals such as magnesium and calcium are also safe to add even in therapeutic levels e.g. magnesium fed for calming, providing the level will not unbalance the diet.
During the final three months of pregnancy, mares should be fed a vitamin E and selenium supplement, since this can help boost passive transfer of immunity to the foal. Such a product needs to be fed on top of a vitamin and mineral supplement or balancer, or the full recommended amount of a fortified compound feed.
Please be aware that the information given here is not definitive, and each product needs to be checked carefully for suitability before use. If in doubt contact the manufacturer.