When we assess the conformation of foals, we must remember that they are not miniature, fully formed horses, but developing horses.
The horse is remarkable in many respects and unique in one. He stands almost immediately after birth, so that he can follow his mother and the herd. This is not unusual in many large herbivores, which need to escape predators, but what is unique to the horse — and indeed to all equids, including the donkey and three species of zebra — is that he stands upon the tip of his only toe.
This extraordinary anatomical feature has led to the horse’s pre-eminence as an athlete among domesticated animals. It is also, clearly, a weakness. With just one column of bones and one toe within each limb to rely upon, these structures need to be well aligned to function efficiently.
When I studied foals’ hooves for my recent PhD project, I was struck by how little we know about this critical time of conformational development.
Foals double their bodyweight in their first month and treble it by two months of age. As a foal stands up within minutes of birth, his hooves are subjected to immediate loading. At two months, those same little newborn feet are supporting three times their birthweight.
Dynamic growth
Hoof renewal is the term used to describe how quickly a horse grows a completely new hoof.
It has been known for many years that a mature horse takes about a year to replace a hoof. The length of this process in foals was unknown until I measured it for my PhD project.
From birth, foals take only four to five months to renew their hooves. A foal is also growing hoof far quicker than his dam: 15mm per month, compared to her rate of 6mm per month.
As a foal has a foot that is half the size of his mother’s, then proportionally his hoof is growing at four times her rate. It is probably growing so fast because, in nature, a small, thin hoof would not have the same ability to resist wear as the rest of the herd. Another reason for the rapid hoof renewal may be that this is how the hoof capsule copes with the extraordinary increase in bodyweight and thickening of bone. Unlike any other animal, the horse’s hoof surrounds his digit: the equivalent fingernail in a human baby only wraps around about 25% of his finger and so is never going to impede bone expansion.
The drawback with such dynamic growth is that the hoof of a foal distorts easily. It is thinner and more flexible than an adult horse’s hoof and deformation occurs due to uneven pressures from the limb above.
Tensions within the foot also affect hoof shape. An example is a flexural deformity, where the tendon is under tension, pulling and rotating the coffin bone and ultimately causing a club foot.
The hoof angle of a foal is much steeper than that of an older horse and this should not be confused with a club foot. Foal hooves are at their steepest at one month old. The hoof angle then descends, probably throughout the horse’s life, but the most rapid period of descent is from birth until weaning — it will drop from around 60° to under 55° by the time the foal is 10 months old. These figures vary from breed to breed, but the rapidity of descent will be similar.
Uneven hoof wear is another cause of hoof distortion, which is invariably associated with mediolateral (side to side) conformational faults. Most foals begin life with a base-wide, toe-out stance and walk, which helps them to maintain stability while their body strengthens. This places more loading on the medial (inward facing) portion of the hoof wall and pushes the lateral (outside facing) aspect of the hoof wall outwards.
In small amounts, this is a normal, healthy part of hoof development, as mature hooves have a slightly shallower angle on the lateral side. Foals that are “toe-in” are usually of more concern, as limbs tend to straighten during development. Being toe-in at an early stage can worsen to an unacceptable point as an adult.
Regular farriery is essential in the development of strong, symmetrical hooves. The farrier’s role is twofold: to remove excess hoof growth and to improve hoof shape, reducing uneven compression in both the hoof and the limb. This has a beneficial effect upon the growth plates of the limb, helping them to correct limb deviation.
Early diagnosis
Whether you have bred a single foal or breed commercially, it is attention to detail and close examination that will allow you to spot problems early.
You can then deal with these at a time of life when it is still possible to treat them. In other words, expecting there to be some farriery or veterinary treatment for a club foot or an angled fetlock when the horse is a year old will be frustratingly impossible and financially damaging for the breeder. For the horse, it means a lifetime with conformational faults and the inevitable unsoundness issues that always accompany them.
To find faults in time to treat them, breeders and farriers must assess foals early and regularly.
Most foals are born with a slightly flaccid myotendinous (muscle and tendon) structure. This is not surprising, since they have spent 11 months under development, without exercise, in the mare’s uterus. You can therefore expect a foal to lean back on his heels. His natural exercise patterns should bring his toes to the ground by one month of age.
If his hooves are still rocking back at this stage, seek specialist farriery care.
We know that young foals have steep hooves, but a club foot is where the hoof wall is at a considerably greater angle than the opposing hoof.
Club feet are not usually seen until three months of age or more — no horse is born with one. Tight tendons, a condition that can occur between one and four months, will cause club foot if left untreated. This is a flexural deformity, where the muscle or tendon unit is so tense that it lifts the heels of one or both front feet from the ground. It is easily recognised on a level, hard surface, but often missed in a paddock.
So, if you have a foal due in the New Year, view his limb structure from when he is one day old and as often as possible after that. When he is one month old, look again with your farrier, who should trim the hooves.
Trimming should take place every 28 days thereafter, to remove excess hoof and reduce hoof distortion.
Ref Horse & Hound; 16 November 2017