Hello. A family relative is trying to do some research and has gotten stumped. One of her questions is to explain 4 ways to tell a horses age. I was hoping maybe you could help her out. We know that teeth is a definite, but unsure about the other 3. Any help would be greatly appreciated. Thank you for your time! Carrie
Hi Carrie,
Examining the teeth to age a horse is the main method used.
You can read all about that and other horse development and aging facts in the horse time line in my book How to Think Like a Horse.
How to Think Like a Horse by Cherry Hill
There is also an excellent web article Determining the Age of Horses by Their Teeth by Wayne Loch and Melvin Bradley
Department of Animal Sciences, University of Missouri-Columbia
Now as far as other methods which is what you are really after, here are some ideas, some of which are fairly obvious but I feel I must mention.
If the horse is registered, look at the registration papers or contact the breed or association registry to ask for that information.
If the horse is branded, determine who owns the brand and contact them.
If you think the horse might have a micro chip implanted in its neck, ask your veterinarian to scan the horse’s neck with a reader to gain information.
As far as visual methods to ascertain a horse’s age, that comes with experience but even knowledgeable horse people can be fooled. There are certain factors that show a horse is getting older such as sunken areas over the eyes, gray hair, lost of muscle tone and so on. But, for example, not all 25 year old horses will show these signs and not all horses that show these signs are 25 and older if you get my meaning.
If you do come up with other methods to tell a horse’s age, I’d appreciate hearing them because for now, today, this is about all I came up with !
Cherry Hill
Cherry Hill's Horsekeeping 
Hello, I have heard of one other way to determine a horse’s age. As I was told the JA ranch that is around what is now Amarillo, Texas would not break a colt to ride until it was 4 years old. This was said to be estimated by “ribbing” I’ll call it. I am not telling you this is fact, only that it was told to me. When a horse is born and under 4 years old, it’s ribs are “webbed” together in a mass. As the colt turns 4, this “web” opens up and goes away starting from the front, then each added open rib beyond to the rear is 2 more years.. The JAs would use a hand poked with the smallest fingers to feel this “gap”. It shouldn’t be all that hard to research this with known age horses as a start. Anyone that can surf the internet better than me can find some data, as well as carcass study maybe in an old textbook, or ?? It makes sense to me that if this is plausible it would be more accurate, as say identical horses under different conditions of grazing vs. stable kept on ground feed are going to have much different teeth after 20 years.
I have aquired a thoroughbred horse from a friend of my husband bout year and half ago. we know nothing bout her and are tryin to learn more bout horses and how to care for them.I am wanting to know her age and what maybe wrong with her since she was just givin away.She has lots of muscle loss and one back leg bows out when she walks-like its dislocated or was broken. any information you can send my way is greatly appreciated. thank you. DawnPeres
http://www.horsekeeping.com/horse-articles.htm