Breeding soundness evaluation

Keywords: bull, bovine, BSE, ejaculation, EEJ, penis, semen, scrotal, tape, circumference

Several of these images appear in a video on breeding soundness evaluation in ruminants; the bull, ram and buck. In addition to other images, they are presented here for your use. As usual, right clicking on an image and selecting "save as" will allow one to see and save an image at full resolution.

One may choose to skip the accompanying text altogether. For some however, it will serve to put the images into context. 

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Bulls should be evaluated for breeding soundness before purchase and routinely, before each breeding season. A BSE is also performed if a bull is suspected of being infertile.

Although a bull may have normal genitalia and semen, he is useless if skeletal, muscular, foot or eye pathology prevent him from breeding. For this reason, a general physical examination is essential. This concept is illustrated below:

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Obvious predispositions to problems such as preputial prolapse (below) and undesirable scrotal shape should be pointed out to owners.

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Because of more efficient heat loss, a pendulous scrotum is preferred over a straight-sided or wedge-shaped  scrotum that holds the testes close to the body. Scrotal shape should be evaluated with the testes fully descended in the scrotum.

Defects such as scrotal shape and pendulous, prolapsing prepuces are generally not used in evaluations to fail bulls. Instead they justify which bulls are preferred over others as potential herd sires.

Routine tests for venereal diseases such as Campylobacteriosis, Trichomoniasis or even systemic problems such as persistent shedding of BVD, are generally not part of a routine BSE but may be where these diseases are of concern.

Before semen collection can commence, transrectal examination of the accessory glands and internal inguinal openings must be performed. This is shown below.

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The scrotum must be palpated thoroughly for normal tone and resilience as well as any evidence of orchitis, neoplasia, epididymitis and inguinal herniation. This is especially the case when the scrotum appears to be asymmetrical or when transrectal palpation suggests that an internal inguinal ring is enlarged and may contain omentum or a loop of bowel. Trans-scrotal ultrasonography can be used to confirm the diagnoses of all these conditions.

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Three factors are used to assess the breeding potential of a bull. These are: sperm motility and morphology and scrotal circumference. Even when it is evaluated by Computer Assisted Semen Analysis (CASA), motility only has a low correlation with the fertility of a bull. Nevertheless, this correlation is statistically significant and as such, remains part of routine bovine BSE. CASA is not typically used for bovine BSE.

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The scrotal circumference of a bull is measured using the specially-designed scrotal measuring tape shown above. The scrotum of this bull had a circumference of approximately 50 cm which is large for any breed and by any standard.

Scrotal circumference in bulls is positively correlated to sperm output and negatively correlated to the age of female offspring at the time of puberty. However, scrotal circumference is dependent on the age of the animal and on the breed as well. The table below shows the minimum acceptable scrotal circumference for a bull of a given breed at a specific age.

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The image below shows the scrotal measurement of a two year old Limousin bull; unacceptably low, even for that breed (see the table above).

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Severely hypoplastic testes in a one year old Angus bull. These testes are too small to even warrant consideration of the bull as a herd sire.

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When possible, libido and mating ability are assessed by the farmer and supplied as part of the history. When these data are absent, a major flaw in routine bovine BSE becomes evident.

Semen can be collected by electrical stimulation or through the use of an artificial vagina (AV). However, AVs are usually used for frozen semen production because a bull must be trained to serve an AV and this is usually not possible for a routine BSE. Transrectal massage of the intra-pelvic section of the penis may produce ejaculates on occasion but is generally unreliable.

Electroejaculation  (EEJ)is achieved by using a large intra-rectal, lubricated probe with several electrodes that run caudal-cranial on its ventral surface. The probe is placed in the rectum and increasing rhythmic electrical stimulations are applied until erection and ejaculation occur. Stimulations usually last for 1 to 2 seconds and discontinued for about ½ second. This is continued until ejaculation occurs. Modern systems are programmed for optimal stimulation,

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The voltage applied is very low. In fact, an intrarectal probe can easily be held in the hand while applying maximum stimulation. However, the ionic environment of the rectum and the proximity of the stimulus to the pelvic nerves are sufficient to cause erection and ejaculation.

EEJ causes muscular activity in the hind quarters, occasionally vocalization and probably a degree of discomfort as well. For that reason, it is considered to be inhumane and is prohibited in some countries. However, this author believes that EEJ can be humane when used properly. EEJ, its effects and alternatives are well reviewed in the selected references given below.

It is essential to support the bull with a chest band during EEJ (see the yellow arrow below) so that he does not collapse in the crush if excessive muscle contraction occurs. In the author's hands it has often been possible to obtain semen samples with minimal muscle contraction. If the bull vocalizes, the author usually ceases stimulation immediately. Occasionally it is not possible to obtain a sample via EEJ.

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During transrectal palpation and by massaging the intra-pelvic section of the penis, one can often induce pulsation and partial erection. Once the penis is extended, it can be grasped using a piece of gauze to avoid slippage (inset at upper right in the image above). This allows the operator to inspect the penis closely before proceeding with semen collection. If massage does not induce partial erection, slight stimulation with the electroejaculator may be used for that purpose. On occasion, the penis cannot be exposed or examined and ejaculation occurs within the preputial cavity.

Semen samples obtained by EEJ (inset at lower right in the image above) are of equal fertility to those obtained with an AV but the volume of the ejaculate is usually higher and the concentration lower, than samples obtained with an AV.

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The image above shows equipment used for routine BSE. The paperwork is necessary for documentation of  the BSE. The special scrotal circumference measuring tape is that shown in earlier images. The two short black tubes hold clear plastic cones, connected to test tubes for semen collection. Note that these devices have long handles on them so that one does not have to reach in under the bull during collection; avoiding possible injury by kicking. Two or more collection vessels should always be available in case the first vessel becomes contaminated with urine. If this occurs, one can switch collection immediately to the second vessel. 

A sleeve for rectal palpation is seen under the collection vessels. This is used to perform transrectal palpation.

The motility of the semen is evaluated subjectively immediately after collection. The sample must be kept at 35° to 37° C on a warming surface until it is examined. Any slides and cover slips must be warmed to the same temperature. 

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Microscopic examination of a drop of semen placed on a slide under low power will reveal wave motion if the motility is normal and sperm concentration is high.

In a normal sample one expects at least 60% of spermatozoa to exhibit progressive motility. Other spermatozoa are either immobile or exhibit bizarre motility such as oscillatory, vibrating or rotating motion. If the density of the semen is high, it can be diluted with 2.9% Na citrate or saline to observe the motility of individual spermatozoa. Several commercial semen extenders can also be used for this purpose. An alternative is to trap sperm within a bubble under a cover slip. This will also allow observation of the motility of individual spermatozoa. (video - pending insertion)

For critical evaluation of motility, phase contrast microscopy is useful. In addition, sperm smears should be stained with modified Blom's or a Diff-Quik stain and examined using regular microscopy. These smears should be stored as a part of the bull's permanent record. Good quality optics are essential and only high-power magnification (1000 to 1250 x) should be used to examine the morphology. At least 200-300 sperm cells should be examined in each sample.

Semen should be free of blood, inflammatory cells, foreign materials and cells from the germinal epithelium. These are referred to as Cells other than sperm  or COTS. Abnormalities are described on the BSE record. See inset at lower left in the image above.

In the ejaculate shown below, the sample was highly contaminated by COTS, due to an abrasion on the penis that hemorrhaged when the penis became erect.

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One should bear in mind that motility can easily be reduced by urine and blood contamination, cooling or improper handling procedures. Motility is also somewhat dependent upon morphology, because abnormalities of the tails of sperm cells will reduce their motility.

In some cases, sperm cell motility may improve with subsequent ejaculations, especially if the bull has not been used for some time.

Sperm deformities such as bent tails, midpiece droplets, expanded midpieces, loose acrosomes and misshapen heads are often encountered.  Abaxial attachments are considered normal in some species where they occur in large numbers in fertile males (boars for example) but their significance in bulls remains debatable. In low numbers, the significance of abnormal spermatozoa is questionable. In normal ejaculates, 60 to 70% of the spermatozoa show no abnormalities. In the image below, normal sperm are shown in the left inset image. In the right inset image, numerous sperm have abnormal morphology, their presence indicated by arrows.

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The image below shows the exquisite morphologic detail revealed by Nomarski, interference contrast. This tool is not use routinely for BSE but should be considered in cases of special interest.

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When potentially heritable defects such as this Dag-like defect (named for a renowned Danish Jersey bull) are seen, tools such as scanning electron microscopy can be employed to study the condition and report on its presence to a breed society. Even further transmission EM study may be needed to confirm the diagnosis of certain conditions. It should be emphasized that such investigations are not commonly performed.

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Bulls are usually classified as satisfactory, questionable or unsatisfactory potential breeders, or have their classifications deferred. Note the use of the word potential, i.e. a bull may appear normal in all respects but may still be infertile due to abnormalities of the spermatozoa that cannot be appreciated on routine examination. One can never guarantee the fertility of a bull. Also, it should also be borne in mind that the judgment of the breeding potential for any particular bull is valid only on the date of examination.

When indicated, bulls can be re-evaluated at a later date. The time required for spermatogenesis in bulls is about 60 days. Another 11 days should be allowed for sperm transport through the epididymis. These figures should be taken into account when one recommends re-evaluation.

BSE forms can be obtained from the Society for Theriogenology (SFT) and the Western Canadian Association of Bovine Practitioners (WCBP). They are similar in content. Both the SFT and WCBP offer software for recording and retrieving BSE results. These programs also allow one to print BSE results for clients and accumulate valuable data for research.

Selected references:

Palmer, C. 2005. Welfare aspects of theriogenology: Investigating alternatives to electroejaculation of bulls. Theriogenology. 64: 469–479

Whitlock, B.K. et al. 2012 Electroejaculation increased vocalization and plasma concentrations of cortisol and progesterone,  but not substance P, in beef bulls. Theriogenology. 78: 737–746

Hematoma penis

Keywords: bovine, penis, hematoma. infertility

Rupture of the tunica albuginea of the corpus cavernosum causes hematoma formation where the retractor penis muscles attach to the distal part of the sigmoid flexure. It is common in all beef breeds (most dairy breeds are used for A.I.) but anecdotal data suggests that it may be most common in Herefords.  Rupture occurs when the tunica albuginea of the corpus cavernosum is stretched beyond capacity. This is believed to happen if a cow goes down under a bull during service or if the bull lurches forward excessively during copulatory thrusts. 

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The image above shows a stylized, dissected penile hematoma superimposed on a view of a bull with hematoma penis. Alterations were made by the author to both images and they were then combined. Copyright in both cases is unknown. Please contact Dr Rob Lofstedt (lofstedt@upei.ca) to further identify copyright and permissions. 

The dorsal nerve of the penis bifurcates proximal to the sigmoid flexure and as shown below, forms left and right branches over the flexure. The red ring overlying the distal flexure in this image shows the most common site for rupture of the tunica albuginea.

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The tear in the tunica can be transverse or oblique. During erection, venous drainage of the corpus cavernosum is occluded and the ischiocavernosus muscles contract, raising the internal pressure in the penis far beyond that of systolic pressure. Using internal pressure transducers, estimates have ranged between about 30lbs/sq inch (~1560 mm Hg) to almost ten times that pressure. Therefore, when rupture occurs, it is not surprising that the dorsal nerves of the penis are often damaged as well. The dorsal nerves provide sensory input from the distal portion of the penis, including the glans penis. Therefore an inability to seek a cow's vulva and penetrate successfully is a common sequel to this injury.

After rupture of the tunica albuginea, large hematomas form in the retropreputial area, causing prolapse of the prepuce with its concomitant problems. Evidence of this can be seen in the top image of this entry. Also, hematomas may become infected, forming abscesses in this area. Therefore antibiotic treatment is essential in these cases. Generally speaking, rupture of the corpus cavernosum carries a guarded prognosis.

Although 30 to 50 percent of bulls may recover with conservative treatment, surgery may allow up to 75 percent to return to service and is recommended when warranted by the value of a bull. That level of success suggests that the dorsal nerves are not severely damaged in most cases or alternatively, they have a remarkable ability to regenerate. Importantly, surgery should be performed soon after injury before adhesions form.

References:

Ashdown, R.R. 2006. Functional, developmental and clinical anatomy of the bovine penis
and prepuce. CAB Reviews: Perspectives in Agriculture. Veterinary Science, Nutrition and Natural Resources 2006 1, No. 021 29pp.

Becket, S.D et al 1974. Corpus cavernosum penis pressure and penile muscle activity in the bull during coitus. Am. J. Vet. Research 35: 761-764

Gnemmi, G. and Lefebvre, R.C. 2009. Ultrasound Imaging of the Bull Reproductive Tract: An Important Field of Expertise for Veterinarians. Vet Clinics N.America: Food Animal Practice. 25:767-79

Hopper, R.M. and Wolfe, D.W. Online 2014 Restorative surgery of the Penis. Bovine Reproduction. Wiley online library.

Lewis, J.E. et al. 1968. Blood pressure within the corpus cavernosum penis of the bull. J.Reprod. Fert. 17:155-156

Roberts, S.J. 1986. Veterinary obstetrics and genital diseases. Infertility in male animals, pp 796-799. Published by the author, S.J. Roberts.

Spiral penile deviation

Keywords: penis, bovine, corkscrew, anatomy, infertility

This image shows severe spiral ("corkscrew") deviation of the penis of a three year Polled Limousin bull. As is typical, the bull had produced calves from his first breeding season but during his third year of life and second breeding season, the owner had observed spiral deviation during the bull's attempts to breed.

 

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The image was taken during stimulation with an electroejaculator. Pre-ejaculate accessory fluid can be seen dripping from the penis.

Notes:
Under certain conditions spiral deviation can be considered normal; about half of the bulls in one study (where a transparent artificial vagina was used) showed slight to pronounced spiral deviation during ejaculation. However, the problem arises when pronounced spiral deviation occurs before penetration, preventing penetration itself. The incidence of that situation varies considerably, but in a large study in New Zealand, just over 10% of the tested bulls showed this problem. It is interesting and potentially important to note that there have been at least two independent observation (one Australian and the other North American) where spiral deviation was more common in polled than horned bulls. This suggests that the condition has a heritable nature; something to bear in mind when considering corrective surgery.

One may ask why it is that even normal bovine penises have a tendency to spiral when fully erect. After reading Ashdown and Smith's paper, the author dissected the terminal portion of a bulls penis to assess its peculiar anatomy first-hand. The image below is the product of that dissection, some 31 years ago! It has been sharpened and annotated for clarification.  The anatomy of the bovine penis is not symmetrical. The apical ligament widens out distally from its origin, about 20 cm proximal from the glans. Strangely, it is attached firmly to the left side of the corpus cavernosum but on the right, its attachment could be described as "flimsy".  Ashdown had a more elegant description and also described an asymmetric arrangement of collagen fibers in the tunica albuginea of the corpus cavernosum itself.

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In the image of the author's dissection, the dotted green line (A) indicates the firm and thick attachment of the apical ligament to the tunica albuginea on its left side. The dashed black line (B) marks the approximate dorsal center line of the penis. The apical ligament itself (C) is shaded green. The thin and rather flimsy attachment of the apical ligament to the tunica albuginea on its right side is marked by the red dotted line (D).

During erection, the blood pressure in the corpus cavernosum penis increases to about 200 kPa  or (~30psi, close to the pressure in a car tire) or higher, expanding it distally. As the corpus cavernosum expands maximally, it pushes against the thin and loosely attached right side of the dorsal ligament. This allows the corpus cavernosum to "break away" and move sideways and distally from the sturdy, linear attachment of the ligament on the left side. That part of the ligament therefore provides an axis for a spiral deviation to form. This is further explained in  the diagram below.

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As mentioned, some degree of spiraling is normal but when the right-sided attachment between the corpus cavernosus and the dorsal ligament is stretched beyond its normal limits, the penis begins to spiral prematurely, preventing penetration.

Several surgical approaches have been described to treat excessive, premature spiraling. One of these (braiding of the dorsal ligament) aims to strengthen the attachment between the apical ligament and the dorsal section of the tunica albuginea through fibrous tissue formation. Autogenous transplants of fascia lata to this area have the same outcome but introduce additional tissue strength as well. Carbon fiber implants merely strengthen the dorsal and right side of the area of attachment between the apical ligament and the tunica albuginea.  Although success (return to breeding) has been reported with all methods, they have not been compared in controlled studies. Also, the rate of relapse has not been well documented.  Because the potentially heritable nature of spiral deviation (recessive, dominance or penetrance)  it is probably prudent to avoid surgery in these cases.

References:

Anderson, D.E. 2008. Surgery of the Prepuce and Penis. Vet. Clin. North America: Food Animal Practice. 24: 245-251

Ashdown, R.R. and Smith, J.A. 1969.The anatomy of the corpus cavernosum penis of the bull
and its relationship to spiral deviation of the penis. J. Anat. 104:153-159

Becket, S.D et al 1974. Corpus cavernosum penis pressure and penile muscle activity in the bull during coitus. Am. J. Vet. Research 35: 761-764

de Blockey, M.A.B. and Taylor, E.G. 1984. Observations on spiral deviation of the penis in beef bulls. Australian. Vet. J. 61:141-145

Lewis, J.E. et al. 1968. Blood pressure within the corpus cavernosum penis of the bull. J.Reprod. Fert. 17:155-156

McDiarmid, J.J. 1981 "Corkscrew penis" and other breeding abnormalities in beef bulls
 N. Zealand. Vet. J. 29:35-36

Mobini, S. 1982. An experimental evaluation of the response of the bull penis to carbon fiber implants Cornell Vet. 72:350-360

Pearson, H. 1974. Corkscrew penis: relapse in a bull after surgical correction, Corkscrew penis: relapse in a bull after surgical correction. Vet. Record. 94:225

Seidel, G.E. and Foote, R.H. 1969 Motion picture analysis of ejaculation in the bull. J. Reprod. Fert. 20: 313-317

Whitsell, D. 1969. Deviations of the bovine penis Iowa State University Veterinarian. 31. Article 5. 25-28.

A penile hair ring

Keywords: penis, infertility, hair, ring

A hair ring around the base of the glans penis in a young bull. The bull was presented for phimosis (an inability to extend the penis) and the presence of a purulent preputial discharge. The hair ring had caused abrasion, posthitis (inflammation of the preputial cavity) and adhesion formation.

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It is thought that hair rings form during attempts at breeding, as a result of the penis moving across the rump of females that are shedding their winter coats. This seems likely because it is during the breeding season that cattle shed their coats.  The loose hair from the female is carried into the sheath, rolling up on the penis as shown here. Therefore, the hair seen on the penis is not that of the bull, but the female he has attempted to breed. Also, anecdotal data (there is a paucity of published data on the condition) suggests that it is most common in young bulls. This is understandable because young bulls have higher mounts per service ratios than older bulls i.e. in a young bull, it is likely that his penis will travel across the rump of the female (seeking the vulva) more frequently than in older bulls, before copulation occurs.

Hair rings are also commonly seen in young bulls penned together e.g. during feeding trials (Dr Rocky Crisman, docroc@peak.org, personal communication). In such cases, bulls may mount one another to establish dominance within the group.

Hair rings can cause urethral constriction as well as posthitis and adhesions.  In small herds therefore it may be feasible to run females into chutes and occasionally brush their rumps during the breeding season.

References:

Gray et al. 2011. Hair coat shedding in Angus cows.  2011 Beef Improv. Fed. Conference. Bozeman, Montana.

Infectious balanoposthitis 

Keywords: IPV, IBR, Herpes, bovine, penis

These images show cases of infectious balanapothitis (IBP); one of many manifestations of infection by Bovine Herpes virus type 1. They include  infectious pustular vulvovaginitis (IPV) in females, infectious rhinotracheitis (IBR) and uncommonly, necrotizing meningoencephalitis (the latter is usually caused by Herpes type 5).

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At the outset it was stated that these were cases of IBP but it is not possible to say with certainty if that was so. No attempt was made to grow virus from the lesions and PCR was not performed in either case. This is a common situation because the disease is considered to be ubiquitous and self limiting. Nevertheless, the lesions seen here are typical of those described for the syndrome in bulls. These red vesicles usually become secondarily infected by bacteria, forming small pustules. This can cause reluctance to breed but the lesions are generally considered benign, healing without treatment. This is very similar to the situation in females, where the syndrome commonly manifests itself as infectious pustular vulvovaginitis (IPV). 

Infectious bovine rhinotracheitis (IBR) is far less benign than either IPV or IBP, characterized by embryonic death, abortions and weak calves. Perhaps obviously, a respiratory syndrome occurs as well.

Interestingly, many bulls that have no history of breeding may show signs of IBP. This is not too surprising in view of the fact that transmission can occur by a number of routes, including airborne infection, fomites, semen and vertical (placental) transmission. Equally interesting have been findings that show that animals with genital infections may shed the virus in nasal secretions without showing respiratory symptoms. Although strain differences do occur, it is intriguing to contemplate how this can occur because numerous studies have shown the virus to be the same in both genital and respiratory syndromes.

In the cases shown here, it is possible that the bulls could be sources of infection throughout their lives because the virus can become latent after the acute phase of the disease. Apparently herpes viruses tend to lie latent in the trigeminal ganglion with shedding occuring in times of stress. Although one could speculate that the virus may lie elsewhere in states of latency, reports cite only the trigeminal ganglion as area for latent virus to reside.

A pertinent question in a case such as this would be: "Can semen from bulls such as these be used to produce embryos that will not transmit IBR/IPV to E.T. recipients and their calves?" This is particularly important when bulls have excellent genetics and international export is contemplated because IBR has been eliminated from several European countries. Although the virus is highly damaging to embryos, those that survive are generally free of herpes virus, even if trypsin is not used in the washing process. However, a small proportion of embryos can still carry virus. Therefore the risk of transmission through ET is considered to be low but potential losses may be too high to contemplate. 

References:

• Engels, M. et al. 1981 Comparison of the genomes of Infectious Bovine Rhinotracheitis and Infectious Pustular Vulvovaginits virus strains by restriction endonuclease analysis. Archives of Virology 67:169-174
• Parsonson I.M, 1964 Infectious pustular vulvovaginits in dairy cattle in Victoris. Australian Veterinary Journal 40: 257–260
• Bielanski A. et al. 2014 Risk of transmission of Bovine Herpesvirus-1 (BHV-1) by infected semen to embryo recipients and offspring Reprod Domestic Anim 49:197–201
• Rissi D.R. and Barris C.S.L, 2013Necrotizing Meningoencephalitis in a Cow Vet Path 50: 926-929

Persistent bovine penile frenulum

Keywords: frenulum, penis, bovine

A persistent frenulum of the penis found during a breeding soundness examination of a bull.

This image was submitted by Dr P. Irons (P.Irons@murdoch.edu.au). Dr Irons was unable to determine the author and copyright holder for the image. If you are, or know the author of this image, please contact Dr Henry Annandale at henry.annandale@murdoch.edu.au.

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The penile frenulum develops as the genitalia are masculinized during fetal development. It is thought to break down under the effect of androgens with the approach of puberty. Understandably therefore, its persistence has been linked to androgen deficiency or the suppression of androgen stimulation. However literature searches reveal a lack of objective data in that regard.

In most cases, the frenulum does not persist beyond a year of age but occasionally frenulums are found during routine breeding soundness exams in yearling bulls. This is a source of concern for bovine practitioners, unsure as to how the problem should approached. Some of this uncertainly arises because frenulums may break down spontaneously after bulls have failed breeding soundness evaluations.  Also, the heritability of this condition is not known. A study on 1,200 yearling Angus bulls did not demonstrate that persistent frenulums were heritable. However, the authors acknowledged that the size of the study limited the value of that conclusion. In short, more research is required on this subject.

Perhaps obviously, bulls with persistent penile frenulums are unable to copulate normally.

In view of the value of some bulls and uncertainty surrounding the condition, some practitioners are inclined to transect the frenulum and dismiss it as an incidental finding.  

Selected references:

Ashdown R. R.  1960. The adherence between the free end of the bovine penis and its sheath J Anat. 94 198–204.

Christmas, R.A. et al 2001. Genetic relationships among breeding soundness traits in yearling bulls. Cattlemen's Day, Kansas State University, Manhattan, KS, March 2, 2001