Shipley CF. 1999;3:117-120 Breeding soundness examination of the

	May and June, 1999

Breeding soundness examination of the boar

Clifford F. Shipley, DVM, Dipl ACT

Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign,1008 West Hazelwood Drive, Urbana, Illinois 61802

Shipley CF. Breeding soundness examination of the boar.Swine Health Prod. 1999;7(3):117-120.

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Summary

This article describes the procedure for conducting a breedingsoundness examination in the boar, including collection of a history,examination of the genitalia, semen collection and evaluation,and suggestions for culling criteria.

Received:February 27, 1997
Accepted:January 10, 1999

rtificial insemination (AI) has becomean increasingly common practice in the swine industry, and thevalue of boars for both AI and natural mating has also increased.It is therefore important to promote routine breeding soundnessexaminations (BSEs) on boars, which can help to identify pooror questionable breeders before they affect herd fertility and/ordestroy an AI stud’s reputation. It will also protect the buyerif a prepurchase BSE is performed or is part of the purchase agreement.Reputable sellers generally welcome a BSE because it establishescredability and reduces the number of boars that have to be replacedfor lack of breeding performance/infertility.

Many of today’s boars go through extensive serologic testingand isolation procedures for disease control. Matching healthprofiles between herds is crucial. For some boar studs and theircustomers, it may be disastrous to introduce boars of unknownor questionable disease status into the herd. An epidemic diseasemay affect all the boars and their subsequent fertility, or maybe transmitted via their semen to other swine herds.

If the boar performs poorly on a prepurchase BSE, much time,energy, and money could be saved. A prepurchase BSE can identifyboars with penile hypoplasia, persistent frenulum, poor or nolibido, penile lacerations/scarring, poor/no sperm motility, inadequatesperm numbers, poor sperm morphology, and musculoskeletal problemsthat prevent mating or mounting a collection dummy, and boarsthat are "bleeders." A BSE can also identify cases ofmasturbation/"balling up" of the penis into the preputialdiverticulum, a condition that is surgically correctable.¹

A BSE should be used as a screening test, not as a predictorof fecundity. Fecundity can only be assessed through 50 test matings,which are the ultimate "bottom line" that measures aboar’s value to a breeding herd. ABSE, however, can identify boarsthat should be immediately culled.The swine industry wouldgreatly benefit if unacceptable boars could be identified beforetime and money is invested in them.

History

The first step in a BSE is to take a thorough animal history.The age (accurate–not an estimate) of young boars is especiallyimportant because their spermiogram will change during puberty.The record should include boar name or identification (number,tag, earnotch, tattoo) and breed and should note previous sexualexperience, type of housing, rearing conditions, show record,body condition, production records, history of any previous exams,libido, mating ability, type of mating system (e.g., AI, hand,pen), farrowing rates, litter size, herd of origin, disease status,results of any testing (i.e., disease[s] and porcine stress syndrome),the frequency of past collection/breeding, past injuries, illness,treatments, and the preventive medicine program of the boar’sherd.

The boar’s fertility may also be affected by temperature extremes,so it is important to ask whether the boar has ever been febrileor has been exposed to high ambient temperatures.^1-3Fertility may also be affected by exposure to extreme cold (-18degrees C) for more than a day. In this extreme weather, testesare held close to the body, increasing the temperature to whichthey are exposed.³

Clinical exam

All boars should be evaluated for locomotion defects priorto purchase. Most producers can make an adequate examination ofthis function, but many boars are now delivered sight unseen andwhen they are found to be unsound, trauma during shipping or transportis blamed. However, many lame boars may have degenerative jointdisease (DJD) or osteochondrosis (OC).^4,5 Nearly 100%of commercial animals are affected with one or both of these conditionsif one examines the ulna, femur, and humerus.⁵ Theseconditions are heritable.⁶If the boar is clinicallylame he may still be evaluated, but you should consider how thelameness may affect his ability to mount.

In addition to locomotion defects, boars should be examinedfor signs of atrophic rhinitis and internal and external parasites,and should be serologically tested for selected diseases suchas pseudorabies virus (PRV, Aujeszky’s disease virus),Brucellasuis, porcine reproductive and respiratory syndrome virus(PRRSV), swine influenza virus (SIV), transmissible gastroenteritisvirus (TGEV),Actinobacillus pleuropneumoniae,Mycoplasmahyosynoviae, leptospirosis (six strains), and porcine stresssyndrome (if the status is not known).

Examining the genitalia

Palpate and measure the testes (Table1). They should be symmetrical, firm, and slightly resilient.Some studies have observed the left testis to be slightly largerthan the right, although if this difference is not found to bestatistically different,² it is not a concern. Accuratetestes size can be measured using real-time ultrasound.⁷

The epididymides should be palpated. They should be symmetricalfrom left to right; bilateral abnormalities are rare. The headsare usually very firm and the tails are usually tense and quitelarge (4-5 cm in adult boars).

The prepuce and preputial diverticulum should be examined forsigns of irritation or infection, and evidence of preputial diverticulitisshould be investigated. Some boars collect large amounts of urinein the preputial diverticula or masturbate in them. Evidence ofblood, excessive urine, semen, or gel may warrant further investigationand treatment or surgery.⁸

The penis is best evaluated during the semen collection phaseof the BSE. Fully extend the penis to examine it for persistentfrenulum, lacerations, ulcers, scars and evidence of hair or beddingmaterial irritation/infection/damage. Penile development and erectionalso should be evaluated. Incomplete erection¹ canbe evaluated during natural or hand collection while penile hypoplasiais probably best evaluated under anesthesia.

Examine the teats, noting the number, spacing, quality, andevidence of "pin" or inverted nipples. These factorsappear to be heritable, so if you note defects, the sons or daughtersshould not be retained for use as breeding animals.⁷

The scrotum should be free of scarring, abscesses, thickening,irritation, or evidence of mange. The testes should be freelymovable within the scrotum and no excess fluid should be palpable.Some fluid may be present, especially in older boars, but itssignificance relative to semen quality is not known.⁷I have found ultrasonography to be most beneficial in furtherdiagnosis of scrotal problems.

Semen collection

Three methods of semen collection have been used for the boar:

• artificial vagina,
• gloved hand, and
• electroejaculation.

Artificial vagina

The artificial vagina was the first method used,²but has fallen out of favor because it is so easy to collect semenby hand.

Gloved hand technique

The gloved hand technique has been described by various authors.^1,7,9An accurate spermiogram is best obtained if the boar has had 2-4days of sexual rest before semen is collected. It is importantto use a vinyl rather than a latex glove because some latex glovesare spermicidal.¹⁰ As the boar mounts either a dummyor receptive female, form a cone with the collecting hand, lettingthe boar thrust into the coned hand. As the penis enters the hand,grasp it by the glans penis, applying pressure only to the distalcoiled portion of the penis. If pressure is applied to the shaftof the penis, the boar may lose his erection and dismount. Ifthe grip is firm enough, the boar will extend his penis fully,stabilize his stance, and start to ejaculate. With extremely shyboars, it may be necessary to allow the boar to enter a sow andthen retract the penis smoothly and quickly by hand to allow collectionto continue in the gloved hand. Some boars may have handler andpressure preferences.

Collect the semen in a prewarmed 37 degrees -38 degrees C containerwith a 300-500 mL capacity, with gauze or a filter loosely stretchedacross the opening to separate out the gel fraction. I use twocollection containers so that I can collect the sperm-rich andsperm-poor fractions separately. Ejaculation usually takes 3-5minutes, with some boars going through two or more ejaculationcycles, which can extend the collection period up to 20 minutes.Boars should be allowed to go through a complete cycle and dismounton their own to keep bad habits from forming or making them reluctantto collect in the future.

The presperm fraction, about 5-15 mL in volume, is usuallyclear and should not be collected. This is followed by a gel fractionwhich will be separated out by the gauze. The creamy sperm-richfraction follows the gel fraction, but can be interrupted by clearvesicular gland fluid as well as more gel. This variation is normal.Normal ejaculate volume will range from 100-300 mL in young boarsto 100-500+ mL in mature boars. Volume will vary based on age,response to collection and frequency of collection; as such, semenvolume is only important when calculating total numbers of spermatozoa.

Electroejaculation

Electroejaculation (EE) is also an option and is particularlyuseful for collecting difficult/dangerous-to-handle boars. Semencollected using EE is comparable to semen collected using thegloved hand technique.¹¹

Anesthesia is necessary for EE and presents some risks as wellas added costs. Porcine stress syndrome-positive animals are atextreme risk, and this information should be obtained in the historyor ascertained by testing prior to EE. Porcine stress syndromerisk is reduced if acepromazine (0.5 mg per kg bodyweight) isgiven prior to anesthesia. The owner should be appraised of therisk of anesthesia whenever electroejaculation is performed. Inmost cases, 5-10 minutes of light general anesthesia is all thatis required for sample collection. Anesthesia also allows a muchbetter chance to observe and palpate the penis, testes, and epididymidesfor abnormalities.

It is usually easy to gain access to the medial or marginalear vein. We prefer to restrain the boar with a snare. Apply atourniquet to the base of the ear, and introduce a 21/23 gaugebutterfly catheter into the marginal ear vein, and then give theanesthetic agent(s) by bolus. Intravenous (IV) administrationreduces the cost of anesthesia compared to available intramuscular(IM) anesthetics, but requires more skill and materials.

Although no anesthetics are approved for use in the pig inthe United States, several different anesthetics/combinationsof anesthetics are available and work well.^1,2,8 Theveterinary-client-patient relationship guidelines are necessaryfor this procedure, and proper withdrawals prior to market shouldbe followed. Anesthetics that work well include:

• sodium thiamylal 1 g IV bolus (10 cc total volume);⁹
• thiopental sodium 6-18 mg per kg IV;¹²
• tiletamine and zolazepam (Telazol^(R)) 2.0 mg per kg IV or 4.4-6 mg per kg IM;
• Telazol^(R) reconstituted using 250 mg (2.5 mL 100 mg per mL) xylazine + 250 mg (2.5 mL 100 mg per mL) ketamine administered at 1 mL per 75 kg bodyweight IV;¹³ or
• 4.4 mg per kg bodyweight Telazol^(R), 2.2 mg per kg xylazine and 2.2 mg per kg ketamine given IM.¹³

No preanaesthetic will usually be necessary. The latter dosageIM will give good surgical anesthesia for short procedures suchas preputial diverticulectomy, detusking, vasectomy, etc. Allthe above anesthetics have a fairly wide margin of safety andmore can be given, usually at 1/4 to1/2the original dose for longer procedures. We have had good successgiving additional dosage necessary after induction via the anteriormammary vein or abdominal vein. This vein is usually found subcutaneouslyjust lateral to the teats.

Once the boar has been anesthetized, place him in lateral recumbencyand clean the rectum of feces and lubricate it. Exteriorize thepenis either by manual manipulation or by inserting a closed Bozemanatraumatic uterine forcep into the prepuce, rotating and openingthe instrument to allow the penis to enter the jaws, closing theforceps and then gently extracting the penis. Once extracted,the penis is grasped with a piece of gauze to prevent occlusionof the urethra. If done properly, this procedure causes no damageto the penis and may be the only way that a hypoplastic penisor a persistent frenulum can be identified. Insert a boar probe,which is approximately 35 cm long and 3.75 cm in diameter withsix annular electrodes fixed at a 5-cm length from the end ofthe probe, into the rectum.^9,14 Any of the adjustablemodels for bull EE are adequate. Begin stimulation at low levelsand repeat it at 4-5 second intervals with a period (5-10 seconds)of rest between stimulations. Most boars will ejaculate within4-5 stimulations and many will continue to ejaculate during theresting phase, especially if the probe is gently moved in andout of the rectum a few centimeters during this time. One maytry to collect the whole ejaculate at this time or simply collectenough of the sperm-rich fraction for evaluation.

Semen evaluation

When evaluating semen, you should assess:

• concentration,
• motility,
• morphology, and
• total sperm numbers.

Concentration

Concentration is the number of sperm per mL of semen. It canbe estimated crudely by color:

• in a watery to opalescent sample, sperm cell concentration will range from 0-200 x 10⁶ per mL,
• in a milky sample, sperm cell concentration will range from 200-500 x 10⁶ per mL, and
• in a creamy sample, sperm cell concentration will range from 500-1000 x 10⁶ per mL (Evans.Proc 7th Ann SC Large Animal Medicine Shortcourse, 1993:45-51)_.^1,5,9

Concentration can also be calculated using a hemacytometeror by photometric means. Photometric measurement uses light transmissionabsorbance as the means to calculate concentration. Because ofdifferences in seminal plasma and sperm density, the machine mustbe calibrated for the proper species (i.e., bull and stallionsettings will not give proper readings for boars). Accuracy ofthe sperm count using photometry will also vary, but it is a fastand a fairly reliable way to estimate sperm concentration.

Motility

Sperm motility should be evaluated as soon as possible aftercollection. Temperature changes, exposure to sunlight, disinfectants,water, etc., will all affect sperm cells detrimentally.⁵Examine a drop of undiluted semen on a prewarmed glass slide andobserve for wave motion. Then, cover the drop of semen with acoverslip and attempt to estimate progressive motility. If thesample is too concentrated, dilute it with an isotonic medium(0.9% saline) and observed under a coverslip again for progressivemotility. When in the field, you can trap a small air bubble underthe coverslip and observe motility around the edges of the airbubble as well as morphology of the trapped sperm in the thinlayer of the air bubble. A normal boar ejaculate should have >70% progressively motile sperm.^3,6

Morphology

Morphology should be evaluated at 1000x magnification. Stainingis not necessary if using phase contrast or differential interferencemicroscopy (DIC), but is necessary if using light microscopy.Diluting the semen sample by placing a drop or two of the semeninto 1-3 mL of formal buffered saline will make it easier to directlyobserve the sperm with phase contrast, DIC, or light microscopy.Morphology stain (eosin-nigrin) is easily obtained from the forTheriogenology (Hastings, Nebraska). Normal semen should not containany blood, pus, or other foreign materials. If it does, a furtherdiagnostic workup may be warranted; or the boar can be culledimmediately, or a reexamination can be performed at a later time.

Examine at least 100 cells and then classify the cells as eithernormal or abnormal. The age of the boar must be taken into accountwhen doing this, because young boars (6-7 months of age) willhave a higher percent of abnormalities (e.g., cytoplasmic droplets,abnormal heads) than older boars.³ Some boars may alsoreach puberty at a later stage or have suffered an injury or infectionthat delays spermatogenesis. Defects that should be noted in themorphology classification include proximal droplets, abnormalheads, coiled tails, midpiece defects, head defects (include acrosomes),bent tails, and detached heads (Table2).^2,15 Total abnormal morphology of sperm cellsshould not exceed 25% in natural service or 20% in boars usedfor AI. This total includes both proximal and distal cytoplasmicdroplets.¹⁴ Distal droplets are not related to a decreasein fertility except when a concurrent increase in proximal dropletsis seen.^5,14 Abaxial tail attachments are normal inthe boar.⁵

Boars with anormal spermiogram (i.e., fewer than 20%-25%abnormal sperm cells per ejaculate) but that have a history oflow litter size may warrant further investigation for a chromosomalabnormality. Up to 50% of hypoprolific boars may exhibit a chromosomaltranslocation. A blood sample for cytogenetic evaluation may besent to the veterinary diagnostic labs at the University of Minnesota,the University of California-Davis, or the University of Saskatchewanin Canada.⁵

The culling decision

After carefully evaluating all parts of the BSE, the evaluatormust predict the breeding future of the boar and classify himas satisfactory, questionable, or unsatisfactory. A single exammay not adequately predict breeding soundness and further examsmay be warranted.

Breeding soundness examinations of boars can be a valuabletool in selecting and culling boars for natural mating or AI.While not the ultimate test of fertility, it is the only practicalmethod we have to predict breeding potential without expendingmore time, effort, and money on test matings and comparing farrowingrates and litter sizes. Boars with a high percentage of motileand morphologically normal spermatozoa are usually very fertile.(Evans.Proc 7th Ann SC Large Animal Medicine Shortcourse,1993:45-51). Those not meeting these criteria should either beculled or reevaluated at 30-60 day intervals. Boars being routinelycollected for AI, especially from boar studs, should be examinedat least once a month and after any illness or injury. Likewiseboars being used in a natural mating system should be examinedroutinely (quarterly). Many commercial operations routinely useheterospermic matings or pooled semen to compensate or cover forthe subfertile boar (Evans.Proc 7th Ann SC Large Animal MedicineShortcourse, 1993:45-51). If we can identify subfertile/nonfertileboars, the savings to the swine industry would be significant.

References

1. Gibson CD. Clinical evaluation of the boar for breedingsoundness: Physical examination and semen morphology.CompCont Educ. 1983;5(5):5244-5249.

2. Holst SJ. Sterility in boars.Nord Vet Med. 1949;1:87-120.

3. Crabo BG. Reproductive examination and evaluation of theboar. In: Youngquist, RS, ed.Current Therapy in Large AnimalTheriogenology. Philadelphia, PA: W.B. Saunders, Co.; 1997:664-670.

4. Hill MA. Skeletal system and feet. In: Leman AD, Straw BE,Mengeling WL, D’Allaire S, Taylor DJ, eds.Diseases of Swine.7th ed. Ames, Iowa: Iowa State University Press;1992:163-195.

5. Hilley HD. Skeletal abnormalities in the pig. In: Biehl,L.G., ed.The Veterinary Clinics of North America, Large AnimalPractice, Diagnosis and Treatment of Swine Diseases. Philadelphia,Pennsylvania:W.B. Saunders Co.; 1982;4(2):225-258.

6. Reiland, S. Osteochondrosis in the pig. PhD Dissertation,Royal Veterinary College, Stockholm, 1975.

7. Hurtgen JP.Reproductive Examination of the Boar.Manual for the Society for Theriogenology; 1984.

8. D’Allaire S, Leman AD, Drolet R. Optimizing longevity insows and boars. In: Tubbs RC, Leman AD, eds.The VeterinaryClinics of North America, Food Animal Practice, Philadelphia,Pennsylvania: W.B. Saunders Co. 1992;8(3):545-558.

9. Morrow DA. Semen collection from the boar. In: Larsen RE,ed.Current Therapy in Theriogenology 2. Philadelphia,Pennsylvania: W.B. Saunders;1986:969-972.

10. Ko JCH, Evans LE, Althouse GC. Toxicity effects of latexgloves on boar spermatozoa.Theriogenology. 1989;31:1159-1164.

11. Basurto-Kuba VM, Evans LE. Comparison of sperm-rich fractionsof boar semen collected by electroejaculation and the gloved-handtechnique.JAVMA. 1981;178(9):985-986.

12. Bolin SR, Runnels LJ, Bane DP.. Chemical restraint andanesthesia. In: Leman AD, Straw BE, Mengeling WL, D’Allaire S,Taylor DJ, eds.Diseases of Swine. 7th ed. Ames, Iowa:Iowa State University Press; 1992:933-942.

13. Wertz EM, Wagner AE. Anesthesia in pot bellied pigs.CompCont Educ. 1995;17(3):369-380.

14. Evans LE. Electroejaculation of the boar. In: Morrow DA,ed. Current Therapy in Theriogenology. 1st ed. Philadelphia,Pennsylvania: W.B. Saunders, Co.; 1980:1037-1040.

15. Althouse GC. Evaluating porcine semen for artificial insemination.Part 1. Standard Tests.Comp Fd Anim Med Mngmnt. January1997:S30-S35.

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