I have often heard it said that no two horses are exactly alike. I agree, but with the millions of horses, it occurred to me that there had to be more than a few that are pretty much alike. That means what works on a particular horse may work on the next horse with similar conformation.
In the discussion of horses' feet, I am constantly amazed in the lack of clarity there is in terms of describing the physical foot. I think we need to be more analytical in the measurements of feet. I have developed a hoof-grading system that I use successfully to communicate to my clients the degree of conformational problems I have to deal with in their horses.
The Renchin Hoof-Grading System
My grading system was inspired by equine veterinarian Ric Redden's grading system for club feet. It is a number system starting from the ideal foot, which I call a Good foot, and falling in increments of 1 to a –4 (minus 4). I do have a grade of -0.5, which is very close to a good foot.
With the foot on he ground, the grade takes into consideration the dorsal wall angle, the heel angle, the coronary band profile, and the lower leg profile, which includes the pastern angle and length. With the foot raised, I look at the hoof shape, the sole depth, the frog characteristics such as width and depth and the strength of the heels. I have found that certain types of feet are very predictable for developing potential problems. This has helped me in better management of the foot before things go bad.
The Good Or Ideal Foot
With the foot on the ground, my ideal foot will have a dorsal wall angle of 52 to 55 degrees, depending on the breed. Western breeds tend to have shorter steeper pasterns, so ideally their angles will be higher than those of a Thoroughbred or warmblood. These angles fall in the sweet spot of not too high and not too low. I like to call this the "Goldilocks Foot."
The ideal foot also has sufficient heel strength to support the heel during the reset cycle and so the hoof will not change angles. The coronary band is straight from toe to heel with no downward dip at the heel. The pastern length and angle are judged by envisioning a line down the front of the cannon bone to where that line bisects the foot. In the ideal foot, that point will be at the widest part of the foot, about two thirds of the way back from the toe.
Looking at the foot with it picked up, the hoof shape will be from wide to medium in width, the sole will be moderately concave and the frog will be moderately full and flush with the heels of the trimmed foot. The heel tubules will be of sufficient strength to support the foot during the reset cycle with out the foot changing angles.
Red Renchin's "good" or ideal foot has a dorsal wall angle of 52 to 55 degrees and sufficient heel strength to support the heels. The coronary band is straight from toe to heel with no downward dip at the heel.
The -0.5 Foot (It's Still Pretty Good)
The -0.5 foot is very close to the ideal foot, but during the reset cycle, you will find the angle will decrease from 1 to 2 degrees. The foot will have sufficient strength, however, to be trimmed back to the original angle.
The -0.5 foot is very similar to a good foot, but the dorsal wall angle may decrease by 1 or 2 degrees between shoeings.
The -1 Foot (Things Are Starting To Slip...)
The -1 foot will be from 50 to 51 degrees at the dorsal wall. The coronary band will be almost ideal, but will be closer to the ground at the heel than in the ideal foot. The plumb line test will bisect the foot about seven-eighths of the way back — almost to the heel. The raised foot will have a medium width with a slightly flatter sole than the ideal foot. The frog will somewhat wider and will protrude slightly beyond the trimmed heels.
In a -1 foot, the dorsal wall angle is from 50 to 51 degrees and the coronary band will be closer to the ground at the heel than in the ideal foot.
The -2 Foot (Then to Slide...)
The -2 foot will be from 48 to 49 degrees at the dorsal wall. The coronary band will have a pronounced dip down to the heels about three quarters of the way back. The plumb line test will bisect the foot at the point of the heels. The raised foot will have a narrow width, flatter sole depth and the frog will be wider and below the level of the trimmed hoof walls.
In a -2 foot, the dorsal wall angle decreases to from 48 to 49 degrees at the dorsal wall. The coronary band will have a pronounced dip down about three quarters of the way back toward the heels.
The -3 Foot (Then To Crash...)
The -3 foot is like the life of a bull rider, it is not a question of if there will be a disaster but when and how bad. The dorsal wall angle will be from 46 to 47 degrees. The coronary band will descend to ground level at the heels. The plumb line test will usually bisect the foot 1/2 to 3/4 inch behind the heel. The raised foot will have a narrow width, a thin, flat sole, a very wide frog that protrudes below the trimmed heels and very weak heels that will often be horizontal with the ground.
The -3 foot is where trouble truly starts. The dorsal wall angle will be from 46 to 47 degrees and the coronary band will descend to ground level at the heels.
The -4 Foot (You Really Don't Want To Know)
The -4 foot luckily is rarely seen in horses in active work. You will see them in cases of severe neglect, but they can often be rehabilitated back to a higher grade of foot.