A recent study found that heel contraction was more common in shod than in barefoot horses, but did not confirm that metal horseshoes were to blame.
Contracted heels have been defined by the ratio of frog length to frog width. The foot can be described as contracted when the frog’s width is less than 2/3 its length. The affected foot is less able to absorb concussion and may lead to lameness.
Magdalena Senderska-Płonowska, with colleagues at the Wrocław University of Environmental and Life Sciences, Wrocław, Poland, assessed the influence of shoeing and other risk factors, such as age, paddock access, and breed, on heel contraction.
The 114 horses included in the study were of various warmblood breeds, and were being used as riding-school horses, pleasure horses, and sport horses. They were considered to be sound by their owners or riders, were at least three years old, and came from yards across Poland.
One group had been kept barefoot all their lives; the others had been regularly shod with metal shoes for at least the previous year.
Senderska-Płonowska measured the width and length of the frog of all four feet of the horses in the study. She found that individual horse features, such as yard and breed, had the most significant impact on the width:length ratio of the frog.
There was a significant difference in the occurrence of heel contraction between yards. Breed was also an important factor. Silesian and Arabian horses had significantly greater frog width:length ratio compared with other breeds.
Being shod did not affect the frog width:length ratio.
A full report of the research has been published in the Journal of Equine Veterinary Science.
Senderska-Płonowska described heel contraction as “a multifactorial problem, mainly caused by breed and unknown features correlated with the individual. The results disputed the popular myth of metal shoes being main cause of contraction, an important factor for all hoof-care providers to be aware of“.
Because of the significant difference in the incidence of contraction between yards, she suggests the need for more research on larger groups of well-defined phenotypes of horses from yards with low and high incidence of heel contraction to identify the environmental factors responsible.
Do Metal Shoes Contract Heels? – A Retrospective Study on 114 Horses. Magdalena Senderska-Płonowska, Paulina Zielińska, Agnieszka Żak, Tadeusz Stefaniak. J Equine Vet Sci (2020) 95:103293.