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.
An Australian colleague notes that the term Breeding fitness examination (BFE) is used in preference to Breeding soundness examination (BSE) in Australasia. No convincing argument is given for that nomenclature therefore it is unlikely the the term BFE will ever be adopted in North America. However, being respectful of Australian views, terms such as "boomerang" and "kangaroo" will be retained for use in both the US and Canada.
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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 Campylobacterosis, 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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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.
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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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,
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, it 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 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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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 samples 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. 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)
In a normal samples 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. 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.
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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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.
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
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
