Persistent penile frenulum in boars
Keywords: porcine, boar, penis, boarThis image shows a persistent frenulum in a boar. The thin penis shows that this is a juvenile animal. The frenulum is usually present on the ventral surface of the penis, therefore this penis has been rotated in the direction of the arrow.
Image size: 832 x 629px
Author and holder of copyright: Dr Sherrie Clark, Associate Professor. VA-MD Regional College of Veterinary Medicine Blacksburg, VA 24061. sherrie@vt.edu
It is commonly suggested that a deficiency of androgenic activity (production or binding) is complicit in failure of the frenulum to break down with the approach of puberty. Castrated boars, dogs and male cattle may have persistent penile frenulums, substantiating that statement. However, in many or most males (the literature is unclear in this regard) the frenulum will break down, even in castrated animals. For example, in a sample of over 400 boars of which approximately 80 percent were castrated, the incidence of persistent frenulum was less than 5%. It is also common to find dogs castrated before puberty that do not have persistent frenulums.
A perusal of the literature suggests that the mechanical effects of attempted erection may play a role in frenulum breakdown as well as the direct effect of androgens. Therefore an absence of mechanical effects may contribute to persistence of a frenulum as well. Erection is largely, but not completely controlled by androgens therefore the relative importance of androgens and mechanical effects on frenulum breakdown is not known.
In the swine industry, persistence of a frenulum is easily detected when hand mating is practiced. It can also be seen during breeding soundness evaluation. In these cases, leniency is seldom exercised and affected boars are almost always culled from herds.
In newsletters and breed reports it has been suggested the condition is probably heritable and that surgical correction should be used only in commercial herds. In essence however, the heritability of the condition is not known and to the author's knowledge the effect of severe culling practices on the incidence of persistent frenulums (an indication of heritability) in the swine industry has not been examined.
The image below is a composite of the common appearance of persistent frenulums in boars. In these animals, the thin membrane connecting the penis to the parietal surface of the prepuce has disappeared. Only a band of tissue remains. Compare this to the image at the top of this entry.
Image size: 1095 x 795px Holder of copyright of both images is probably Dr Lawrence Evans, retired. Permission for use granted by the Department of Theriogenology. College of Veterinary Medicine · Iowa State University · Ames, Iowa 50011. Dr Swanand R Sathe. BVSc, MVSc, MS, DACT. ssathe@iastate.
References:
R Singh, R., Parihar N.R., 1998. Congenital anomalies in swine male genitalia. 68: 324-327
Shipley C.F. 1993 Breeding soundness examination of the boar. Swine Health Prod.7: 117–120
Althouse G.C. 2014. Applied andrology of Swine. Chapter 15 in Animal Andrology: Theories and Applications. Eds. Chenoweth P.J. and Lorton, S.P. ISBN 13:978 1 78064 316 8
