How much weight can a horse safely carry?

Q: I’m concerned that I may be too heavy for my horse. Staying fit is a constant battle for me, and right now I weigh 175 pounds at 5 feet, 5 inches. My Quarter Horse-cross gelding is 14.1 hands, but sturdy at about 900 pounds. Am I too heavy for him?

A: The basic rule of thumb for a horse’s weight-carrying capacity is 20 percent of the horse’s weight, or, say, 200 pounds for a 1,000-pound horse. (Two hundred pounds would be an approximate upward limit, not an average of what he can carry.) That means a 900-pound horse like your gelding, in general, shouldn’t be expected to carry more than about 180 pounds, including tack, to avoid putting excessive stress on his joints and ligaments.

(Obviously, this rule of thumb assumes that the horse in question is at a healthy weight. A horse that’s grossly overweight at 1,200 pounds, for instance, can’t necessarily carry 240 pounds.)

All that said, there are many variables that affect this rule of thumb. One would be the type and build of the horse, regardless of his overall weight. A tall, relatively lightly built horse that weighs 900 pounds is, in general, going to be less able to carry weight comfortably and safely than a 900-pound horse that’s shorter and more compact—in other words, sturdy, like your gelding. The amount of bone a horse has—meaning the size of his weight-carrying large bones, as indicated by the circumference of the cannon bone—is closely related to the sturdiness factor. The more bone, the better, with respect to a horse’s ability to carry weight and stay sound.

Then, too, your overall fitness (as opposed to just your weight) is also a factor. A strong, fit, well-coordinated but heavier rider can often be easier for a horse to bear than a weak, unfit, awkward but lighter rider.

Your riding ability comes into it, as well. Skill and experience will enable you to be better balanced at all times, which makes you easier to carry at any weight.
So, overall, assuming that (1) you’re reasonably fit for riding and have good basic skills; (2) your horse is indeed a sturdy fellow with reasonable bone; and (3) your tack doesn’t weigh an additional 100 pounds, you should be fine.

Founder vs Laminitis 

Q. - I hear a lot of people use the words laminitis and founder interchangeably. Are these two conditions the same thing?

 A. - That's a more difficult question to answer than you might expect, because the two terms are used interchangeably by a lot of people. However, "founder" implies more of the chronic condition, or the horse that has already had its coffin bone rotate or sink. That is classically a "foundered" horse, versus a laminitic horse that has the onset inflammation of the laminae, which support the coffin bone within the hoof capsule.

Unusual Spots

Q. Our 11-year-old chestnut Morgan mare has suddenly developed white spots all over her body with no apparent cause. She is outside 24/7. The spots range in size from about dime-size all the way up to silver dollar size. There doesn't seem to be any irritation or irregularity in the skin. It looks like someone splattered her with white paint. Are there any clues as to the cause?

A.  It sounds like your horse is exhibiting a form of vitiligo (also called leukoderma or birdcatcher spots), an uncommon acquired pigmentation disorder characterized by progressive areas of pigment loss. These spots typically are only a cosmetic problem and rarely indicate other problems. There is also no known cause or effective treatment. Veterinarians have seen a higher incidence of vitiligo in some breeds (for instance, Arabians) than others, suggesting there might be a genetic basis.
White hair color can also be associated with trauma such as healed wounds or saddle sores from improperly fitting tack, but this does not sound like the case with your horse. Other causes for vitiligo can include skin damage due to sunburn, sun damage, frostbite, and even infections with the parasite Onchocerca. If you are still concerned about these spots I would recommend talking to your veterinarian about them during your next exam.

Differences in Urine

Q. ~  My two horses' urine output is very different. For instance, the ammonia smell of my Thoroughbred's urine is a lot stronger than that of my Quarter Horse. I read that protein affects ammonia levels--could that be why? And the color of my Quarter Horse's urine (in the snow) has always been of a medium to dark orange, while my Thoroughbred's is, well, yellow. What could be causing this?

A. ~  The kidneys produce urine, which contains waste products that need to be eliminated from the body. These waste products include urea and ammonium ion, two breakdown products of protein. The more protein a horse has in his diet, the more urea and ammonium his body will produce and excrete in the urine. Urea is composed of two ammonia molecules and can be broken down to ammonia after being passed in urine. So the answer to your first question is that the more protein your horses consume, the more urea and ammonium they excrete. This contributes to the ammonia smell in their stalls.

However, if your Thoroughbred and Quarter Horse are eating the same diet, that does not explain the difference between the ammonia smell in their stalls. An additional factor that can play a role can be differences is the normal bacterial flora present in the lower urinary tract. Some horses simply have more bacteria with an enzyme called urease that splits urea back into ammonia molecules. If your Thoroughbred has more bacteria with urease in his lower urinary tract, his body will produce more ammonia and, thus, you will notice a stronger ammonia smell in his stall.
Finally, horses also have varying amounts of compounds called urocatechins in their urine. These can be oxidized by light after they are passed and turn orange to red in color, thereby discoloring shavings. In the winter, they also discolor snow and are often confused with bloody urine. The color change only occurs in urine passed by some horses and not others--the reason for this difference is not fully understood.