Sorry SJ I had a quick look for that article, the internet can sometimes be a black hole. The mare I read it for has just turned 5 and had her first foal. She is an excellent mother, and balances that with being a polite respectful horse. If we would have changed anything we would have given her more contact with the other horses, not that she wasn't with them a lot and now is very involved socially in the herd. The vets initial advice was to remove her from the other mares with an eye toward infections.
As the new studies are now showing kids who grow up with animals tend to have less allergies, some of our old thinking really doesn't cut it. I had a doctor friend who used say "you'll eat a pound of dirt in your life, your body can handle it" Natural is always better and when we get in and do thinks that "make us feel good" we damage our animals for a life time as we go merrily on with our lives.
I will keep poking around for that article, a good friend has just lost an amazing Appaloosa mare so if I can find it I will send it along to him too