...If you raise horses, you need to supplement their food with 10mg of iodine and and 20g of calcium. The rda for humans is 150mcg iodine and 1g calcium. So where in the hell do wild horses get that much iodine and calcium?
Turns out, that in the wild, they get all of both from drinking water that standing on the earth (mud puddles) and also from eating the dirt clinging to plant roots they are eating. So, when I see all those wild critters around the world who seem to be doing just fine with the minerals they need to survive, I worry a little bit less.
Interesting! This might explain why our neighbor's cat specifically comes to our garden once or twice a day to drink from our muddy pond, even though it has a water bowl at home. When I had my own cat I also observed that he would prefer to drink from muddy puddles outside than from his water bowl indoors, I thought he just didn't like the chlorine taste of tap water, but perhaps he also wanted some minerals!
I don't worry about calcium intake either despite not eating much dairy. I figure I get enough from almonds, salmon and green veggies.