편자 뺀 발굽
편자 뺀 맨발굽의 잇점
우리는 왜 편자를 하는지 또는 어떻게 그것이 말의 전반적인 건강에 영향을 주는지 생각하지 않고
말은 편자를 필요로 하는 것이라 추측한다.
하지만 제임스 루니 James Rooney, DVM, and O.R. Adams, DVM가 쓴 말의 파행에 관한 교과서에서는
편자를 하는 것은 필요악이라고 한다.
경우에 따라 기승자의 가중된 무게로 인해 바닥과의 접촉면이 넓어지고 이로 인해 발굽이 심하게 닳는데
특히 딱딱한 지면에서 그러하며 이러한 이유로 편자를 하는 것이 필요한 것이다.
편자를 하는 것이 잠재적으로 나쁜 것은
발굽을 저해하여 장기적으로 말의 건강에 좋지 않은 영향을 끼치기 때문이다.
일을 해야하는 말과 말의 건강사이에 타협점을 찾는다면 일년에 몇주는 편자를 빼고 지내게 하는 것이다.
VMD, PhD, Professor at the College of Veterinary Medicine 미시간 주립대 수의학과의 로버트 바우커박사Robert M. Bowker연구에 따르면 일년에 짧은 기간이라도 편자를 뺐을 때
말들이 다리가 건강해졌다는 것이다.
125마리의 편자를 하지 않은 말들(편자를 해본적이 없는)을 조사를 했는데
이 말들은 주로 쿼터말이었으며 서러브렛과 아랍, 웜블러들과 잡종들로서 거친 자갈밭과
단단한 모래가 있는 지역에서 방목이 되어지며 매주 몇번씩 사람을 태우고 운동을 하는 말들이었다.
이것 외에 10마리의 말들이 가을에서 봄까지 같은 곳에 편자를 뺀채로 풀어놓아졌는데
이 말들은 일반적으로 편자를 하고 시합에 나가던 말들이었다.
약 다섯달 동안 조사를 하려는 목적으로 오른쪽 앞발바닥에 회반죽캐스트를 했는데
이 조사에 따르면 편자를 뺐을 때 점차로 말의 발굽이 건강한 발의 특징을 갖게 되었다는 것이다.
편자를 빼고 3주후에 이 쇼우에 나가던 말들은 발굽모양이 바뀌는 징후가 확실해졌으며
발바닥이 살짝 둥글고 움푹하게 들어가고 넓어지는 경향을 보였다.
가운데 옴푹 들어간 곳은 발꿈치주변에 깊이 골이 지는 대신 더 얕아지거나 열렸으며 발바닥에서 발끝쪽으로
굳은살이 생겨 지면이 닿는 곳에 더 많은 체중을 실을 수 있다는 것을 보여주었다.
편자를 빼고 6-9주후에 제차frog 전체가 더 커지고 발바닥이 더 넓어졌으며 제차가 땅에 닿기 시작하고
이것은 발바닥이 점차로 더 커지게 했다.
이것은 체중을 싣는 면적을 더 커지게 했으며 체중분산을 더 넓게 시키게 하여
발에 가해지는 스트레스를 줄이게 하였다.
검사를 위해 붙였던 회반죽을 보면 제차와frog 바bar가 말의 체중을 지지하는 것을 확실히 보여준다.
수많은 발굽을 해부해 본 바우커 박사에 의하면
이런 적응된 맨발굽은 내면에 문제가 없는 건강한 발굽의 특징과 같다고 한다.
반대로 바우커박사는 어떤 외적인 발굽의 특징이 내적인 문제를 보여주며
잠재적 파행을 일으키는 발굽인지 알고자 하는 것이 목표라고 한다.
....
한 번에 읽어가며 번역하려니 어설프고 지루해서 여기까지....
나머지는 직접 읽으시도록.
His findings show that in healthier feet, the bars on the bottom of the foot make contact with the ground and exhibit a wider angle than feet in worse shape. The paracunal sulci (next to the frog) of these healthy hooves are usually packed with dirt, not manure. It seems that an optimal angle for the bars might be critical to a healthy foot--a wider angle (about 60°) is better than bar angles that are more vertical or upright, such as those seen in contracted feet. Healthy feet seem to exhibit an equilateral (equal-sided) triangle in the distances between the heels and the apex of the frog.
Bowker's information corresponds with studies by Gene Ovnicek, Registered Journeyman Farrier (RJF), and others on wild mustang feet. There has been some controversy over what the data on wild mustangs has to do with shod domestic horses, since mustangs are not subject to domestic conditions. In part, this discussion was due to the idea that wild mustangs were actually a separate species and therefore related to the domestic horse, but different genetically. As it turns out, these herds are actually a melting pot of many breeds, so the designation of "feral horses" is more accurate. What that means is that any differences in the feet of feral horses compared to domestic horses is due primarily to environment rather than genetics. once this is clarified, it becomes evident that environment makes a substantial contribution to hoof health, or lack thereof.
What's a "Good" Foot?
Studies have sought to discover exactly what factors promote the optimal health of the equine hoof. Since problem feet in the wild are generally weeded out by natural selection, the remaining herd forms a perfect sample for observing the characteristics of healthy feet.
There is a considerable overlap in the characteristics of feral horses' feet and the feet of healthy domestic horses allowed to roam barefoot for a few weeks. The overlap between feral hooves' characteristics and those of shod domestic horses is not as great, yet the trends are undeniably similar.
Both studies demonstrated that only when the feet are overgrown is the hoof wall used as the primary weight-bearing surface. In both instances, as long as the horse is allowed to move freely over varied terrain, the hoof wall is filed down in response to the environment with the bars, frog, and sole (especially the callus) bearing a considerable percentage of the horse's weight.
This is an important distinction because of how these weight-bearing dynamics place stress on different parts of the hoof. Bowker found that when a bare hoof is placed on a hard surface, only a small percentage of the foot surface actually bears weight (6-7%), while in the same feet placed on a hard rubber surface, the percentage of the surface area bearing weight increases to about 25%.
The important point here is that as the weight-bearing area of the hoof increases from harder to softer surfaces, the load on the tissues decreases rather dramatically. While the area for support increases as the horse moves from concrete to hard rubber, the actual load in the tissues will be reduced by more than six times. While this difference in load with different surfaces might seem relevant to a discussion of hoof characteristics, consider this: Reducing load by increasing the area of the hoof contacting the ground decreases load on those weight-bearing structures--whether it's because of a softer surface or because of hoof conformation.
Additionally, Bowker's findings showed that when the horse puts weight on a hoof, the hoof wall flexes outward 2-4 millimeters depending on the hardness of the footing. This leaves us with something to think about--if we are artificially impeding this movement by nailing shoes onto the hoof wall, how does that impact the structures of the foot?
Rooney's revised edition of his classic text The Lame Horse also refers to this dilemma. He states that if you draw a chalk line around the foot of a shod horse standing on hard ground, then do the same thing 15 minutes after the shoe has been pulled, you will find that the foot has expanded beyond the original line. The shoe restricts the normal expansion of the hoof.
In addition, the hoof wall has a degree of "fluidity" to it that enables it to move depending upon the surface that the hoof is placed upon. This "fluidness" depends on the moisture content of the hoof wall as well as the qualities of the hoof wall itself. The increased surface area of contact when the hoof is placed upon hard rubber, Bowker believes, is due to both the movement of the hoof wall and the rubber--it is more than sinking into the rubber. All of this confirms the importance of good footing and hoof wall quality to a horse's soundness.
The Sensitive Hoof
Proprioception is the capacity of the nervous system to sense where the body and the limbs are in space, and to evaluate weight-bearing surfaces as well as touch. There are different receptors or nerve endings for different kinds of stimuli, and Bowker's research has focused on receptors that relate specifically to locomotion. This subject has been well mapped out in cats and laboratory rats, but up to this point, little has been done to understand how horses assess the ground beneath them.
The same receptors that stimulate cutaneous (skin) sensations in other species are present in the equine hoof. The hoof is a sensitive and responsive organ, much like (though not quite as sensitive as) the tips of our fingers. This might help explain why their feet (and gaits) respond differently to different surfaces.
The other implication of this is that by altering the bottom of horses' hooves, we might be interfering more than we realize with their perception of the environment. Control of the muscular contractions that stimulate movement depends on information from the receptors about the terrain the horse's feet are encountering, which helps the brain decide how much and how quickly muscles should contract in order to achieve the desired movement. The information from the receptors might be inaccurate if the hoof (their interface with the environment) has been altered.
Environmental Effects
According to Bowker's research, environment is critical in the formation of the internal structures of the equine hoof. The lateral cartilage and the digital cushion respond to their environment and use. In feral horses, the digital cushion is smaller and the lateral cartilage is larger.
The inner portion of the lateral cartilage, closest to the digital cushion, tends to be fibrocartilage (made up mostly of fibers like normal connective tissue) in "good-footed" horses. The evidence of hundreds of Bowker's dissections indicates that the healthier foot is the one that has thick lateral cartilage tissue with considerable fibrocartilage and a digital cushion composed of fibrocartilage, rather than one with a thin lateral cartilage (0.22 inches thick versus 0.4-0.8 inches thick in healthy hooves) and a fatty, elastic digital cushion. In the younger horse (less than four or five years of age), this part of the foot has not fully developed yet; as far as we know, the digital cushion is still composed mainly of fat and elastic tissue.
"We believe that given the correct stimuli, i.e., exercise, the lateral cartilage and digital cushion will respond," Bowker says.
Environment is a very important contributor to the formation and composition of the internal structures of the equine foot. Bowker's findings suggest that the lateral cartilages and digital cushion respond to various stimuli within the environment--i.e., if the foot is used (and stimulated by the ground), the internal structures will respond to support the weight and function of the foot and horse. Conversely, if the horse becomes a "couch potato," remaining in the stall for much of the day or not being given sufficient foot stimulation, the internal foot does not respond or develop into a good foot. In feral horses the lateral cartilages are much larger and thicker than in these "couch potatoes," and the digital cushion is composed mainly of fibrocartilage.
This means that it is important for horses to be allowed access to turnout, preferably over varied terrain on a regular basis. The stimulus of free contact with the environment at least three to five times a week, in addition to regular work, is what generates more resilient tissues inside the hoof. The gradual nature of the change requires a consistent regimen of activity.
"We believe that the more exercise the better, much as with our own health!" says Bowker.
Bowker's findings are confirmed by Ovnicek's work with feral horses. The most striking difference between the feral horses and domestic horses was visible in the feet of feral yearlings, which exhibited enormous frogs. These horses have no option but to be moving at speed on a variety of terrain within an hour of birth. The ensuing size of the frog and apparent health of the foot indicate the beneficial effect: Most farriers know that foals which are turned out will not have as many foot problems as those foals that remain in the "comfortable" setting of the stall on thick bedding.
"It's similar to humans taking our shoes off and walking over a rocky road," Bowker says. "The first time we do it, it hurts our feet, but if we did it all summer we could do it with ease and not even notice it! The horse isn't much different."
Although shoes are quite necessary for some horses to do what humans ask them to, many don't need them and indeed are better off without them. Also, shod horses have been shown to benefit from a period of turnout without shoes. If your horse is constantly shod, you should work with your farrier (and possibly your veterinarian) to decide if some barefoot time should be part of your horse's future. Even without shoes, the hoof should still be trimmed professionally on a regular basis (i.e., at five- to six- week intervals).
FURTHER READING
Bowker, et al. Sensory receptors in the equine foot. American Journal of Veterinary Research, 54, 1840-1844, 1993.
Bowker et al. Functional anatomy of the cartilage of the distal phalanx and digital cushion in the equine foot and a hemodynamic flow hypothesis of energy dissipation. American Journal of Veterinary Research. 59, 961-968, 1998.
Bowker et al. Effect of contact stress in bones of the distal interphalangeal joint on microscopic changes in articular cartilage and ligaments. American Journal of Veterinary Research. 62, 414-424, 2001.
Rooney, James R. The Lame Horse: Causes, Symptoms, and Treatment. Millwood: Breakthrough Publications, 1974.
Stashak, Ted S. Adams' Lameness in Horses, 4th edition. Philadelphia: Lea & Febiger, 1987.