Differences in Wound Healing
between Horses and Ponies

Jacintha M. Wilmink,

DVM

,

PhD

,

Diplomate

RNVA

Horses and Ponies: Same Species, Different
Healing Characteristics
Clinically Apparent Phases during Wound
Healing
Infl ammatory Phase
Formation of Granulation Tissue
Wound Contraction
Epithelialization
First Intention Healing (Primary Wound
Closure)

Second Intention Healing
Infl ammatory Phase
Formation of Granulation Tissue
Wound Contraction
Epithelialization
Clinical Implications
First Intention Healing
Second Intention Healing
Conclusion
References

Horses and Ponies: Same Species, Different Healing Characteristics

Over the course of millions of years the horse evolved from a small forest dweller to a large ungulate which

inhabited the vast open plains of the temperate zone. It became a so-called “fright and fl ight” animal whose
instinctive reaction to danger is to run.

1

Evolution took place as a response to various environmental and climatic

challenges while selection by mankind resulted in the development of special features. Both evolution and
selection led to the large variety of breeds known today.

The equine species can be roughly subdivided into horses and ponies; this is offi cially a matter of the height

at the withers of an adult (ponies are

<1.48 meters). Whether ponies are just small horses has been disputed for

decades. The discussion of this topic, with respect to wound healing, started in the 1980s, when Bertone, et al.
(1985)

2

found in a study on second-intention healing that ponies healed faster without the formation of exuber-

ant granulation tissue (EGT), in contrast to horses. However, other authors reported the development of EGT
in ponies,

3,4

and the faster healing of wounds in ponies could not be confi rmed.

4

Because a difference in wound

healing between horses and ponies might provide information about the basic biology of equine wound healing
and about the complications commonly associated with repair in this species, Wilmink, et al. performed a series
of experiments to investigate wound healing in both horses and ponies. They proved that ponies heal faster
and with fewer complications than do horses

5–7

and demonstrated that these differences were based on the

effi ciency and capacity of the leukocyte to produce several mediators.

8,9

The details of these studies will be dis-

cussed herein.

What remains to be elucidated is the cause of the observed differences in healing between horses and ponies.

It may well be that the longer period of domestication of the horse has precluded natural selection against poor
healing, since the wounded horse was/is tended to by man. Additionally, the artifi cial selection of features such
as height, athletic capacity, and appearance might have favored the development of some diseases and undesir-
able characteristics, possibly including the reduced effi ciency of leukocytes. Moreover, horses with poorly healed
wounds, which limit their athletic ability, are often used for breeding, which may perpetuate the cycle. In

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