What is Mulefoot?
In discussion of newborn piglets or perhaps a hunting trophy you may hear someone refer to an animal being "mulefoot". But what does this actually mean? Is this trait simply a curiosity, or a serious genetic defect?
"[O]f a cloven-hoofed animal : having a solid rather than a cleft hoof" [Merriam Webster]
"Mulefoot" is a term that refers to an animal of a species that usual has a cloven hoof with two toes, but this individual has single undivided hood like a horse or mule. This condition is formally referred to as syndactyly or Mulefoot Disease (MFD) and is caused by a genetic mutation.
What Species Can be Affected?
Mulefoot is recorded as occurring in pigs and cattle, and occasionally other cloven hoofed species, over many centuries,
In cattle either an undivided hood, or extra toes, are considered defects that usually negatively affect the health and gait of the calf.As they grow the hooves become bent or curled and the animal has trouble walking.
The inheritance if by a recessive gene carried on chromosome 15, so both bull and cow must be carriers to pass it to their offspring, and the front hooves are most commonly affected.
In the 1960s and 1970s mulefoot was quite common but careful breeding has almost eliminated it in most breeds of cattle. It occurs due to a single recessive gene and has been most commonly reported in Holstein and Angus cattle.
Because this mutation can occur spontaneously it continues to be found sporadically in many breeds including Holsteins and Korean native cattle.
The Mulefooted Hog: There is currently only one recognized pig breed with an undivided hoof: the mulefoot. The mulefoot pig comes from Spain but is now widely considered and American breed and sometimes said to originate from Oklahoma. This breed comes in many colors, most commonly black and red. The mulefooted hog was very popular early in the twentieth century because it was reputed to be immune to diseases such as cholera. This proved to be an unfounded superstition. the breed is currently listed as critically rare with less than 200 known pure-breed animals alive today.
Other breeds: In other breeds of pig, mulefoot in breeds like this is rare but considered a harmless trait that does not negatively affect the pig. In fact there is archeological evidence that mulefoot used to be quite common in pigs before the development of standardized commercial breeds that are all cloven hooved.
Mukefoot has also been observed in American feral hogs. The presence of this trait in free-roaming wild animals reinforces the idea that it is not a harmful trait in swine.
Rarely Occurring in:
Mulefoot may occur in any hooves animals but there are only very small numbers of reports for most species including goats and sheep. Syndactyly is often associated with other congenital abnormalities and generally considered a harmful trait.
In both species an animal may have mulefoot on only one or two feet, or on all four. When only two feet are effected they are invariably the front two feet.
The difference between a trait and a defect is that a defect has a negative effect on the animal. As such mulefoot should be considered a neutral trait in swine, but a defect in cattle and all other hoofed species.
- Barr, M. (1981). Syndactyly. Angus Journal, 34-35.
- Johnson, E. B., Steffen, D. J., Lynch, K. W., & Herz, J. (2006). Defective splicing of Megf7/Lrp4, a regulator of distal limb development, in autosomal recessive mulefoot disease. Genomics, 88(5), 600-609.
- Leipold, H. W., Schmidt, G. L., Steffen, D. J., Vestweber, J. G. E., & Huston, K. (1998). Hereditary syndactyly in Angus cattle. Journal of Veterinary Diagnostic Investigation, 10(3), 247-254.
- Madgwick, R., Forest, V., & Beglane, F. (2011). Syndactyly in Pigs: A Review of Previous Research and the Presentation of Eight Archaeological Specimens. International Journal of Osteoarchaeology.
- Spillman, W. J. (1908). Report of the Committee on Animal Hybridizing. Journal of Heredity, (1), 317-323.
- Spillman, W. J. (1910). History and peculiarities of the mule-foot hog. Journal of Heredity, 1(3), 178-182.
- Thompson, K. G., Piripi, S. A., & Dittmer, K. E. (2008). Inherited abnormalities of skeletal development in sheep. The Veterinary Journal, 177(3), 324-333.
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