Here is an insightful article on the differences between caring for dogs versus horses. It was written for writers who are not horse people but include horses in their novels. But, if you are thinking about buying a horse, read on!
For example: Woogie likes to share carrots with Sonny, but when they wag their tails it means two different things!
http://bookviewcafe.com/bookstore/sample/writing-horses-sample/
