Though this article refers specifically to the Peruvian Paso horse, it is worth reading information on DSLD.

 
Mechanical Observation Of the Peruvian Horse 
By Ed Houston 
 
My first involvement with the Peruvian horse was in 1972. My breeding program began in 1974 after I purchased a colt. The first five horses I bred became Champion of Champions and I really thought I knew what I was doing. These five champions were all from the same mare. When she died, I bought what I believed to be an even better mare. However, her foals were of less than average quality! That really took the wind out of my sails.

I also bought a granddaughter of a mare from Peru by the name of Distinguida. Unknown to me, this mare had leg problems (DSLD*). I gradually became aware of other Peruvian horses with similar problems. I decided that a successful breeder must define the problem and find means to avoid or correct it.

In 1975, Gerald Gardener, D.M.V. of Thousand Oaks, California and I began studies to find an etiology for weak suspensory ligaments. We had foals from champion mares by champion stallions with severe problems in the suspensories. One colt was so weak in the suspensory ligaments that we had to help him stand in the morning. Another colt's suspensories were so tight he couldn't lie down. So, we named the colts "Up" and "Down".

We postulated the cause of the suspensory abnormalities to be metabolic. We did serum analyses to determine if there was an imbalance of proteins or minerals that might relate to disproportionate development of the bones, tendons or ligaments. Our studies only showed that horses with abnormal calcium phosphorous ratios, have a predisposition to epiphysitis. This was already known. Other veterinarians we interviewed said they had comrnonly seen swelling in the rear suspensories of Peruvian horses. Some of these veterinarians felt this weakness was due to leg size being too small for the body mass.

One veterinarian stated that in his 30 years of experience he had found an inordinate number of Peruvian horses with weak suspensory support of the fetlock.  He felt torn suspensory fibers became replaced by scar tissue. Eventually, some of the scar tissue became calcified and was frequently seen in radiographs of older horses.

Degenerative Suspensory Ligament Desmitis (DSLD) results in edema in and around the sheath of the suspensory ligament. It is initially evidenced as "wind puffs" and may gradually lead to severe tissue edema in the fetlock area, where the suspensory has the greatest stress. We performed Ultrasound tests on weak suspensories and found breaks in the ligament fibers. Surgery to drain tissue from around the disrupted fibers was not beneficial.

I consider the suspensory ligament analogous to a steel cable. A steel cable cannot be repaired by welding. Welding, in fact makes it weaker. As with the suspensory ligament the more fibers damaged, the less load a cable can support. As more fibers break, the support progressively weakens, the pasterns flex toward the ground and the leg below the hock becomes more vertical (post legged).

When the suspensory in one leg breaks down, it transfers more load to other legs and eventually all four legs may be severely affected. In 1976, I began attending judging seminars and passed the test to become a qualified judge. I didn't really want to be a judge much as I wanted to "student judge" with other judges. Hopefully, I could learn why some horses break down at an early age and use this knowledge to strengthen my breeding program.

Some of the factors that seemed to be contributory were long pasterns, small bone and ligaments in relation to body mass, abnormal leg conformation, excessive work at a young age, poor nutrition and improper hoof care. But the $64,000.00 question was why some of the top show horses, with apparently good conformation, were breaking down by the age of 8 to 12 years?

I was student judge or co-judge with 15 different judges and asked each of them why some of the horses were having suspensory ligament failures at early ages. No knew, neither the judges nor the veterinarians!

I waited 5 years for Sr. Alfredo Elias to judge a show in the United States, so I could be a student judge with him. Many people consider him to be the most important breeder of this century. Alfredo owned Distinguida, the granddam of my mare that broke down in the suspensory ligaments. He informed me that Distinguida also broke down. He had her suspensory ligaments examined postmortem and found they were torn where they bent most, at the fetlock joints. My mare showed the same finding. Alfredo said he didn't know why the suspensories broke down, but he could tell which horses would be most prone to this problem by observing the tails of the horses while gaiting. He said, "if the tail moves up and down, the horse is not correct in the rear. The tail should lay still and appear to be sweeping the ground."

I began to watch the horses' tails for movement and noticed that in horses without vertical movement, the point of the hip was in line with the last lumbar vertebrae. In horses with vertical movement, the point of the hip was forward (cephalad) to the last lumbar vertebrae. Also, the farther the hip is forward of the last lumbar vertebrae, the less the horse can over step. I found that horses with hip points in line with the last lumbar vertebrae could over step at a slow walk and horses with the hip points in front of the last lumbar vertebrae would not over step or even cap at a slow walk.

In the course of judging shows, I've had the opportunity to evaluate over 1,100 horses in six countries: Canada, U.S.A., Guatemala, Honduras, Ecuador and Peru. The observation was correct in every case! I could predict with 100% accuracy which horses could overstep at a slow walk by palpating the position of the last vertebrae and noting it's position in relation to the hip.

After co-judging a show in Ecuador with Raul Risso and Annette Kart, a visitor from Peru, Sr. Pedro Koechlin von Stein (Best Breeder in Peru, four consecutive years) invited me to accompany him to Peru and look at his horses. I accepted his offer and later that evening we flew to Lima, Peru.

Sr. Koechlin owns the hacienda that formerly belonged to Sr. Fernando Grana. Fernando Grana is, of course, well known among all aficionados of the breed for his judging and the respect his knowledge commanded. Sr. Koechlin has refurbished the old hacienda and it is truly magnificent.

We looked at all of Sr. Koechlin's horses and I demonstrated to him the relationship between lumbar/hip anatomy and the ability of a horse to over step.

I also told him that every horse I've seen that is broken down in the rear suspensories has the hip point forward to the last lumbar vertebrae. Sr. Koechlin said he was impressed with this observation and wanted me to discuss it with Sr. Rodolfo "Fito" Matellini. Fito spent a lot of time studying the Peruvian horse with Fernando Grana and is widely know as an extremely capable judge.

Peter arranged for Fito to pick me up at the hacienda and take me to the Grand Hotel Miraflores owned by Fito and his brother. Fito and I spent three days indulging our "horsaholic" passion. We reviewed every horse photograph in his office and he showed me that the best horses place their hind leg well underneath the body when moving forward. When a vertical line is extended from a riders shoulder to the ground it hits a point at which the rear hoof should at least reach, and preferably move in front. After showing Fito a picture of a horse skeleton I brought with me and indicated my lumbar/hip observation, he asked if the Peruvian horse has the same number of vertebrae as other breeds. I didn't know.

Fito gave me a book written by Lady Wentworth in England, dated 1938. Fito said to his knowledge it is the most complete book of horse anatomy available. Lady Wentworth described autopsies of horses considered to be pure "Barbs". The veterinary surgeons in Gibraltar say the true Barb is now practically extinct and the last one owned by Lady Wentworth was the last of the traditional breed. The Peruvian horse derived its gait principally from the Barb. Lady Wentworth stated the Barb horse had 19 ribs, 6 lumbar and 18 tail vertebrae. In horses with Arabian blood, there are fewer ribs and lumbar vertebrae. She further states that Barb skulls were different in that the bones were thicker and heavier. There were also differences in hoof structure. So there are reportedly significant skeletal distinctions in the Barb compared to trotting breeds.

In the book, El Caballo de Paso Y Su Equitation by Luis de Ascasubi, he states "some of the Spanish ancestors of the Peruvian Paso breed were very close to pure Barb".

Ascasubi points to similarities between the Peruvian Paso horse and the Barb, such as similar gaits and similar conformation, especially in the neck. Sr. Ascasubi discusses the tendency of some breeders to "repair" the slightly Barb head and sloping croup of Peruvian Paso as a "subconscious Arabian Complex".

Ascasubi also said, "The gait is most accurately judged when a horse is presented at a slower speed. If a horse does not have a good gait when its speed is restrained, the depth of breeding is probably not sufficient, and of course, horses must be able to do more than gait well at slow speeds. Over step is so characteristic of pacing animals that it constitutes a criterion for judging their quality. Under step is nothing less than shameful".

The North African Barb horse was brought to Spain in the 12th century and mixed with horses in Spain. These offspring were called Spanish Jennets. The Spanish Jennet is the horse brought to Peru by the conquistadors in 1536. The Barb was a common looking horse compared to the Arabian and was bred out of existence in Europe. People like to see pretty heads, short backs and high action, all traits of the trotting breeds. Even now, in the showing, you see more value placed on looks, rather than efficiency of movement. To keep the breed pure in the qualities for which it was developed we need to have correct skeleton structure, brio, strength, timing (pisos) and smoothness.

Research can be valuable in respect to DNA and skeletal features, such as the number of vertebrae. This information can help us preserve the purity of the breed.

My personal observations have shown that a horse with a long slopping shoulder of 45 degrees, a 110% or greater hip in line with the last lumbar vertebra, a four beat gait and low tail set, is better gaited and stronger than a horse with a shorter more vertical shoulder, a body length to height ratio of 105% or less, a point of hip in front of the last lumbar vertebra and a high tail set. The latter features are characteristic of trotting horses. Why? Because, as you increase speed you increase pressure or impact (load). As load increases, trotting horses go to two legs of diagonal support. When Paso horses increase speed with a 4 beat tempo, the horses with the hip in front of the last lumbar vertebrae have less over step and subsequently more stress on the suspensory ligaments. Most horses with under reach will pound their rear feet in the ground and "kick sand" forward. They will also have some vertical hock movement, resulting in vertical tail movement. Their rear quarters are being 'jarred up and down" with each step. I've examined a number of older, sound Peruvian Pasos. The one thing they have in common is overstep at a walk. There are rare exceptions, but these horses are compensating with other characteristics and are a subject for further discussions.

In building a structure, the strongest support configuration is triangular. When horses overstep at a walk, the legs form a triangle from the side view. When horses under step, the legs form an inverted trapezoid. Any mechanical engineer will tell you that a triangle is much stronger than a trapezoid. Horses with the point of hip aligned with the last lumbar vertebrae, also tend to have low tail sets and a relatively long, down sloping croup. This is an efficient configuration for swinging the rear limb forward with little vertical movement. I contend that all horses with "gateado" gait will have the pelvic structure just described. And these horses will have a sweeping tail with virtually no vertical movement.

Horses with high tail sets, have a more horizontal pelvis. When the muscles of the pelvic girdle contract, the leg moves up and down. This is the motion of trotting horse. Trotting horses "hop" off the ground to go forward and shift diagonals. But the correct way for a 4 beat gaited horse to move is for the rear legs to swing forward with no vertical hock movement. The tail remains motionless and the energy from the hindquarters is converted to forward motion with minimal vertical impact. The results is more efficient use of the horse's energy, a smoother ride and less stress on the suspensories.

I've also seen Peruvian horses that under step at a walk, have long pasterns, are coon footed and post legged but haven't broken down. However, none of these horses had a consistent 4 beat gait. As they increased speed, they either trotted or paced, thereby reducing suspensory stress by having two legs hit the ground simultaneously.

What are the practical applications of these mechanical observations? I would strongly encourage every judge to evaluate the horses in each breeding division class at a slow walk and look for overstep. If a horse cannot at least "cap", i.e. rear hoof overlap front hoof print, it should be a strong negative consideration. This evaluation can be done very quickly, but is more reliably accomplished after the horses have warmed up. Some horses with correct anatomy may temporarily under step if they are not relaxed. However, one can usually determine over reach in a few seconds.

Stallions with no over reach should rarely, if ever, be used for breeding. Never breed two horses who both lack overstep. The result will usually be disastrous. If a mare lacks overstep, she should only be bred to a stallion known to be pre-potent in correcting the deficiency.

These simple, inexpensive measures can substantially decrease the number of unsound horses while research refines our understanding of suspensory ligament problems.

Posted with permission from the author.


 


About The Author

Ed Houston has been an active breeder, trainer, exhibitor and judge of the Peruvian Paso horse during his involvement with the breed, which began in 1972. He also designed a successful equine recovery tank for reviving horses following surgery. He serves on the PPHRNA Judges's Accreditation Committee and is currently president of the Peruvian Horse Judges Assoc.

His observations as presented here are currently under study at Texas A&M University.

 

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