There are two simple steps in my barn to teaching your horse where to deposit his road apples:
1. Buy new horse
2. Put new horse in pasture with Waldo, the owner’s 20-year-old warmblood
This is the new horse: 
And this is Waldo:
3. Voila! New horse is potty trained!
At our barn, the owner mows a strip just inside the fence perimeter of both pastures and all four horses pass manure ONLY on this strip. It makes cleaning the pasture a breeze because you don’t have to walk the whole field with your muck bucket or wheelbarrow, you just have to go along the fence line where the grass is nice and short.
The strip before cleaning:
The same strip after cleaning!
When we do fecal egg per gram counts on our horses, their numbers are always low to zero. This is due in part because THEY do a great job of separating the “rough” (the area where they pass manure) from the ‘lawn” (the area they graze) and WE do a great job of picking the poop on a regular basis. FYI it takes about 48 hours for a strongyle egg to hatch and become infectious after being passed in a pile.
Lest you think potty training is only for #2, take a look at these sand and wood chip piles in the paddocks for #1:
Not sure if Waldo is also responsible for the Urination Location, but it’s pretty funny to see a horse grazing far out in the field all of a sudden come walking in to one of these spots, stretch out to pee, maybe grab a drink while he’s in, then head back out for more grass. Come to think of it, t’s also pretty funny to watch them walk over to the fence line, TURN THEIR BUTT TOWARDS THE FENCE, and go.
Waldo takes his potty training very seriously, as sometimes he puts his hindquarters right up against the fence so that when he makes a deposit, it actually falls on the other side. But, that’s how you get beautiful pastures like these: 
Lydia F. Gray, DVM, MA SmartPak Staff Veterinarian and Medical Director Dr. Lydia Gray has earned a Bachelor of Science in agriculture, a Doctor of Veterinary Medicine (DVM), and a Master of Arts focusing on interpersonal and organizational communication. After “retiring” from private practice, she put her experience and education to work as the American Association of Equine Practitioner’s first-ever Director of Owner Education. Dr. Gray continues to provide health and nutrition information to horse owners through her position at SmartPak, through publication in more than a dozen general and trade publications, and through presentations around the country. She is the very proud owner of a Trakehner named Newman that she actively competes with in dressage and combined driving. In addition to memberships in the USDF and USEF, Dr. Gray is also a member of the Illinois Dressage and Combined Training Association (IDCTA). She is a USDF “L” Program Graduate and is currently working on her Bronze Medal. Find Dr. Gray on Google+
I use wood pellets for bedding in my mare’s outdoor stall. I make a strip in the back of the stall, and it works! She also urinates about a foot in front of the strip. I’ve come across this way of cleaning the stall by accident, just noticing she poops in the area that’s cleaned deeper than the rest of the area. After reading this helpful article, I’ll be sure to keep cleaning this way. It makes life easier. Thanks.
Hi Lorraine, it’s great to hear your mare has already self-trained in this useful habit! She’s got a good thing going with you looking after her care and cleanliness. Keep up the great work (and please give her a pat from us!). -SmartPaker Jenna
Who taught Waldo?
Hi Sharon, great question! That’s just Waldo’s superpower. He’s got some pretty strong opinions on how “his” farm is run. He’s certainly one-in-a-million! -SmartPaker Jenna
Waldo has always been a fastidious horse. Before he retired, when under saddle in the arena, he would only deposit his manure by “C”, and then try to deftly avoid stepping on it the rest of the ride. He is priceless! He has trained many a horse to be clean 😀
My two horses (mare and gelding) were turned out with a fastidious warmblood “Caesar” who taught them where the bathroom was. We think he did it by being obviously disgusted when they did not use it. I had thought the mare was hopeless but he somehow prevailed. I’ve always wondered.
Exactly how does Waldo get the other horses to follow his lead?
Hi CJ, great question! When Waldo is in the same pasture as the horse passing manure, if they don’t automatically head to the fence to do their duty, he gently herds them in that direction. The funny thing is when the horse is NOT in the same pasture, they’ll sometimes poop anywhere they like because Waldo is not able to physically maneuver them! That is, they know there’s nothing he can do. He definitely notices though, and expresses his displeasure at their laziness. – SmartPaker Lydia