Anyone ever heard of an old wives tale about putting a penny in the water trough of a really cranky mare and it will supposedly put her in better spirits? I'm assuming something maybe to do with copper/menstrual cycle?
Sounds like folk lore. I wouldn't believe it. I'm assuming the logic behind it has to do with copper? A penny isn't going to add any digestible copper into your mare's water, unfortunately.
To get any effect from the copper you would probably have to toss a few pounds of pennies in that trough... Not a bad idea, but I'd rather take my horse to the mall and have him drink out of the wishing fountains they have there ;) Its probably cheaper.