All Natural Herbs for Increasing Estrogen in Mares Just like humans, horses can have hormones out of balance. Your mare may have low estrogen, and something may need to be done to maintain levels of estrogen that are healthy. Mares in need of an increase of estrogen can often be helped through proper diet and supplementation. Silver Lining Herb’s supplements are designed to help support your equine’s health. All-natural herbal supplements, our NASC Quality Seal of approval product is a favorite of many top professional riders, and once you try it, you will likely become one of the horse lovers across the country who recommend Silver Lining Herbs.