Persistent penile frenulum in boars

Keywords: porcine, boar, penis, boar

This 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

Resecting the preputial diverticulae in boars

Keywords: balling, diverticulum. penis, prepuce, porcine, boar

Each preputial diverticulum lies dorso-lateral to the preputial cavity, just caudal to its opening. The diverticulae are poorly developed in castrated males but in mature boars, they are important sources of scent for territorial marking (together with metacarpal, preorbital, and tusk glands).

The preputial diverticulae are a potent source of objectionable odor to humans and harbor Actinobaculum suis (Corynebacterium suis) and other bacteria associated with cystitis. The diverticulae can also be involved in a syndrome known as  "balling up" where the penis enters one of the diverticulae during attempted copulation. The boar mounts the sow but ejaculates within the diverticulum; a cause of infertility. Finally as seen at the bottom of this entry, a rather old but unique photograph shows that the preputial diverticulae may occasionally prolapse through the preputial opening.

In commercial swine production, boars with abnormalities are usually culled from the herd but in Swine A.I. units, these diverticulae may be resected to improve hygiene. In pet Pot-bellied pigs, it is common to remove the diverticulae at the time of castration.

At upper left, this diagram shows the location of the diverticulae and how the penis enters one of the diverticulae. At lower right, the basic approach to surgical removal of the diverticulae is shown.

Image size 1375 x 966 px

Image size 788 x 589 px  Holder of copyright of image is 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.

General anesthesia is induced. After flushing the diverticulae with a dilute iodine solution to cleanse the area and decrease odor, the diverticulae are filled with the same solution to facilitate identification of the extent of the diverticulae (This fluid can be seen within the left diverticulum in the image). A shallow incision is made through the skin, over the bulge of one diverticulum on the lateral aspect of the prepuce. Using blunt dissection, the diverticulae are separated from the surrounding fascia (usually not a difficult process). The diverticulae are then everted through the preputial opening and from within the operative site, a purse string suture is placed around the base of the diverticulae and closed securely. Finally, the diverticulae are resected at the preputial opening and the operative site is closed in a conventional manner.

This image shows prolapsed preputial diverticulae in a boar.

Image size 588 x 402 px  Holder of copyright of image is 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.

Also see: Breeding soundness examination of the boar

Spermatogenesis in a mature boar

Keywords: boar, pig, porcine, spermatogenesis, seminiferous, semen, sperm

A good illustration are spermatogenesis in a mature boar. Sertoli cells are easy to identify in this specimen. Spermatids in the tubule seen at lower left are in the Golgi phase, early in the formation of acrosomes. At lower right, spermatids are in a more advanced stage of development, the so-called "cap phase" where the acrosomes are almost completely formed. At this time the excess cytoplasm from the spermatids is being shed in the form of droplets. Usually mature spermatozoa do not have cytoplasmic droplets but is not uncommon to see cytoplasmic droplets on spermatozoa when there are slight disruptions in spermatogenesis. The very dark and condensed nuclei of spermatogonia can be used to identify their occasional presence along the basement membrane; there are seldom many spermatogonia visible in any section of seminiferous epithelium. At the top of the image, the spermatozoa are in the most advanced stage of any of those in the section, as shown by the somewhat linear and highly condensed chromatin of the spermatids, just before spermiation.

Porcine hemosemen or hemospermia

Keywords: blood, semen, porcine, pig, boar

Injuries to the penis from bite wound and abrasion of the glands during breeding are not uncommon in boars. These can cause transient hemospermia as seen here. Other causes probably abound but a viral cause that has been identified is Porcine Rubula virus (PoRV). Although this fact sheet does not emphasize that fact, it does provide a quick source of information on PoRV, also known by the name of the area in Mexico where it was first discovered i.e. La Piedad Michoacan paramyxovirus (LPMV)

Image size: 1105 x 1781px

Incidentally, it is the view of this author that the finding of blood in an ejaculate should be referred to as hemosemen rather than hemospermia because blood is found in the semen, not the spermatazoa.

Spermatogenesis in pigs; neonate to puberty.

Keywords: pig, spermatogenesis, porcine, testicle

A series of four cross sections of testicles from young boars: a neonate and at three, four and five months of age. In the neonate, spermatogenesis is totally absent and the predominant cell types are Leydig cells (Lc) and spermatogonia (Sg). At three months of age it can be seen that the onset of puberty has begun and primary spermatogonia (Ps) are seen for the first time in this series of images.

Notice that primary spermatogonia have many different appearances, some with tightly packed DNA and others with loose granular DNA and light nuclei. These differences are noticeable between the images but are also obvious between individual seminiferous tubules in the same image. For example, notice the difference in appearance of the primary spermatogonia between one tubule and another in the cross-section from a four months old boar. To understand why this is the case, one must first appreciate that primary spermatogonia are the "showcase" cells for demonstrating most of the stages of meiosis (leptotene, zygotene, pachytene, diplotene, diakinesis); each stage having a distinctly different appearance in these images.

Before  meiosis begins there is an "interphase"(a phase between the normal multiplication of spermatogonia and the onset of reduction division of spermatozocytes). During that time, the amount of DNA in the spermatogonia doubles so that this lengthly process is not required in the later stages of sperm formation when secondary (haploid) spermatozocytes are formed. This is important to remember because it explains why secondary spermatozocytes are so seldom visible in cross sections of seminiferous tubules i.e. immediately after secondary spermatozocytes have been formed, they divide into spermatids which are also haploid but have half the amount of DNA present in secondary spermatozocytes. In these cross sections one can see spermatids such as those in the Golgi phase (G) of spermiogenesis, but no secondary spermatozocytes are visible anywhere.

Understanding the difference in appearance of primary spermatocytes as they pass through the stages of the prophase of meiosis (leptotene, zygotene, pachytene, diplotene, diakinesis) one can appreciate that a sections of tubules adjacent to one another will look different if they are in different stages of meiosis. For example, one cross-section may contain primary spermatozocytes that are in leptotene while an adjacent tubule may contain primary spermatozocytes in pachytene, the cells having a very different appearance to those in leptotene.

Within a particular tubule, meiosis starts at one point in the tubule and adjacent to it, other cells are triggered to start meiosis as well. The biochemical signal that stimulates this is not understood but it is akin to a domino effect with one set of basal cells stimulating those adjacent to it. This progresses along the tubule so that all the stages of meiosis and spermiogenesis (the later stages of sperm formation) could be seen adjacent to one another if one was able to traveled along the "line of dominos" in the tubule. Every "domino" is different and is akin to a set of different cell relationships from basement membrane as meiosis progresses. These cell relationships are called the stages of spermatogenesis. Typically there would be a dozen stages; some more, some less depending on the species In an animal with 12 stages, this would be akin to 12 dominos. Once the set of 12 dominos have all been knocked down, the next set, further along the tube begins to be knocked over. By analogy, spermatogenesis occurs in waves along the seminiferous tubules and there are many waves of spermatogenesis along the entire length of any given tubule. With this physiology in mind, one can then understand why one tubule in a cross-section can appear so different to its neighbor; they are in different stages of spermatogenesis.

The other cells that are visible here are Sertoli cells (Sc). They occur along the basement membrane of the seminiferous tubules and are the only somatic cells to be found in the tubules. They are essentially the interface between the chromosomal variation in the tubules and the rest of the body; the blood;testis barrier. They support the growth and division of spermatogonia, spermatozocytes and spermatids in the process of becoming spermatozoa. This supporting role is both anatomical and physiological, providing FSH and androgens to cells that will become spermatozoa. They are also responsible for production of inhibin and anti-müllerian hormone (AMH), both of which suppresses the development of the female reproductive tract in male animals. Sertoli cells also have numerous other functions Among these are the formation of androgen binding protein to make androgens available for spermatogenesis and remarkably, aromatization of androgens to estrogens so that testicles produce substantial amounts of estrogen. In fact, in stallions (where mole for mole, more estrogens are produced than androgens) estrone sulphate is often used in stallions to diagnose cryptorchidism.

The stain used in these preparation was Periodic Acid Schiff (PAS) a particularly useful method of demonstrating acrosomes and basement membranes in seminiferous tubules.

The entire process of spermatogenesis usually takes between 45 and 60 days depending on the species. In pigs, it is close to 45 days.