Quantitative Study of Hoof Growth and Wear Patterns in a Semi-feral Herd of Ponies

Laura Florence,
Sue McDonnell, and Elkanah Grogan

University of Pennsylvania
School of Veterinary Medicine


            Newly emerging schools of hoof trimming are based on what is purported to be the “natural” wear pattern of the feral horse.  The assumption of the “natural” model is that it promotes and maintains superior hoof health. This is based on relatively consistent observations that wild and feral equids are conspicuously free of foot problems that are common to domestic horses.  In spite of rapid acceptance, the “natural” model is based on descriptive reports of a small sample of free-ranging horses in essentially one region of North America at a single point in time.  To our knowledge, there has been no systematic longitudinal study of hoof health, shape, or growth and wear patterns of horses living under natural environmental and social conditions.  One important controversy concerns the assumption that natural hoof conformation is static.  Since 1994, we have maintained a herd of approximately 65 Shetland-sized ponies, for the principal purpose of studying natural social organization and behavior of equids.  Like other self-maintaining wild and feral horses, this herd has been essentially free of foot problems or clinical laminitis.  Daily observations of this herd and other semi-feral and wild horse populations at various times of the year, suggest cycles of natural hoof growth and wear, resulting in widely varying length and shape.  The growth and natural trimming cycles appear to be influenced by environmental factors, such as nutrition, terrain, weather as it affects the substrate, and annual seasonal changes in locomotor patterns associated reproductive and social behavior.  These factors appear to interact with genetic hoof characteristics.

            The goal of this project is to systematically describe equine hoof conformation, health, and growth and wear patterns of the New Bolton Center semi-feral pony herd, as one example of a self-maintaining population living under natural social and environmental conditions.  Our primary objective is to describe shape, natural wear patterns, as well as hoof health characteristics and morphologic details of a representative sample (40 animals) of this herd at 4-month intervals over a two year period.  Additional objectives include describing variation in

patterns of hoof conformation within and between families, sex, social categories and their associated locomotor patterns (harem stallion, bachelor stallion, mare, juvenile male, juvenile female) and ages.

Hoof measures, both directly from the animal and from clay impressions, as well as visual inspection data are being obtained.  For each hoof, 25 specific physical measures and characteristics are obtained and a clay impression is made from which 14 specific measures and characteristics are subsequently obtained.  Beginning with the third examination (June 2005), to facilitate measure of hoof growth and wear for the second year of examinations, a 1mm wide x 5mm long mark running parallel to and 1 cm distal to the coronary band of each front and hind left hoof was made.  Each hoof is also examined for any signs of disease and injury (laminitis, sole bruising, abscess, sole puncture or crack, fungal infection, white line disease, pododermatitis).


Interim results

            One complete year of measures has been obtained and analysis is in progress.  At this point we can conclude that in fact over that first year, significant variation has been measured.  For example, several measures clearly demonstrate seasonal transition from “normal” short toes and wide heels in the fall to longer toes and narrowed heels (contracted heels) in winter, and then back to a shorter toe and wider heels in early summer.  This example not only demonstrates wide variation in healthy self-maintaining hooves but suggests that a condition considered pathologic in domestic horses may in fact be a normal seasonal phase of hoof growth and wear of the natural hoof.

            Also available for this interim report are data from a recent sub-study in which we measured hoof growth and wear over a 3-week period of observed active trimming coincident with dry summer conditions in which the substrate is hard.  Mean estimated hoof growth over that 3-week period was 7.3 mm (sem 0.5) in the front and 7.0 mm (sem 0.4) in the hind.  Mean estimated hoof wear over the 3-week period was 11.2 mm (sem 0.9) for the front and 7.3 mm (sem 0.5) for the hind.  Natural trimming over that period ranged from 3 to 33% (mean = 16%) of June toe length for the front and 2 to 21% (mean = 11%) for the hind.

This work is expected to contribute considerable new knowledge on hoof conformation, growth and wear under natural social and environmental conditions, and will likely stimulate interest in further systematic study of natural hoof characteristics in additional populations.


This is a Dorothy Russell Havemeyer Foundation Project.