Evaluation of possible methods to reduce pain associated with ...

Evaluation of possible methods to reduce pain associated with electroejaculation in bulls Wendy L. Mosure, Rory A. Meyer, Jon Gudmundson, Albert D. Barth Abstract Heart rate changes were recorded in attempt to objectively measure pain associated with 6 methods of semen collection, including transrectal massage, conventional electroejaculation, and electroejaculation after either intrarectal lidocaine, epidural lidocaine, epidural xylazine, or intravenous xylazine. Epidural anesthesia with lidocaine or xylazine tended to result in smaller heart rate changes.

Evaluation de differents methodes pour reduire la douleur associee 'a l'elecResume troetjaculation chez le taureau. Des modifications de la frequence cardiaque ont ete enregistrees dans le but de mesurer objectivement la douleur associee 'a 6 methodes de recolte de la semence, dont le massage transrectal, l' electroejaculation classique et l'delectroejaculation apres administration soit de lidocaine intrarectale, de lidocaine epidurale, de xylazine epidurale ou de xylazine intraveineuse. L'anesthesie epidurale 'a la lidocaine ou 'a la xylazine tendait 'a etre associee 'a des modifications plus faibles de la frequence cardiaque. (Traduit par docteur Andre' Blouin) Can Vet J 1998; 39: 504-506

Electroejaculation is widely used for semen collection during breeding soundness evaluation in bulls; however, there is some concern about the humane aspect of this procedure (1). Some bulls vocalize during electroejaculation when the highest settings of electrical stimulation are used. Electroejaculation without anesthesia in humans is painful (2) and, therefore, it may be assumed that electroejaculation is painful to animals as well. However, aversion tests indicated that electroejaculation in rams was not more aversive than partshearing (1). Similarly, goats (3) and bulls (4) did not show aversion to handlers or the restraint facilities when electroejaculation was carried out frequently. However, electroejaculation of unanesthetized animals was banned in several European countries in the belief that it is inhumane, and from 1991 to 1995, the European Union prohibited importation of frozen semen that had been collected by electroejaculation (personal communication, R. McRonald, Semex Canada). Studies to find methods to reduce pain caused by electroejaculation may be compromised by the difficulty in objectively assessing pain. Stress or pain, caused by transrectal palpation, IM injection, or venipuncture, was sufficient to result in elevation of blood cortisol in cattle (5). Tail docking, castration, and mulesing in lambs caused significant increases in cortisol and B-endorphin within 15 min (6-8). Blood cortisol and B-endorphin levels have been used to measure response to acute pain due to dehorning in calves (9) and elecDepartment of Herd Medicine and Theriogenology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B4. Address correspondence to Dr. Albert Barth. Reprints will not be available from the authors. The authors thank the Interprovincial Student Summer Research Fund for supporting this project. 504

troejaculation in bulls (10). However, B-endorphin was not released in significant quantities after dehorning in calves, and, although plasma cortisol rose significantly in response to dehorning in calves and electroejaculation in bulls, maximal levels of these hormones were seen in response to restraint alone or rectal palpation alone. At this time, it appears that no reliable endocrine indicators are available to quantify stress or pain experienced by cattle or sheep in response to veterinary and husbandry procedures. Amongst human males, the majority of patients subjected to electroejaculation have spinal cord injuries and do not need analgesics or anesthetics. Those with normal sensation in the perirectal area are given a general or an epidural anesthetic before electroejaculation (1). Therefore, epidural anesthesia may be useful to reduce or eliminate pain due to electroejaculation in animals. The purpose of this study was to evaluate possible methods of reducing pain due to electroejaculation, by using heart rate change as an objective measure of pain. Electroejaculation causes strong contractions of the skeletal muscles of the hindquarters, so elevation in heart rate during electroejaculation might be due to both pain and muscle exertion. However, it was postulated that reduction of pain would result in a smaller increase in heart rate, which would be due mainly to muscle exertion. Intrarectal topical lidocaine, epidural lidocaine, epidural xylazine, and IV xylazine might reduce the pain caused by rectal smooth muscle spasm or intrapelvic nerve stimulation. A secondary objective was to determine whether the methods used would interfere with penile protrusion and semen emission. A 3-year-old Horned Hereford bull, a 2-year-old Simmental bull, and a 2-year-old South Devon bull that were habituated to the handling facilities and had been electroejaculated, were used in 2 replicates of the experiment. During restraint, the bulls were prevented Can Vet J Volume 39, August 1998

from moving back and forth, but their heads were not caught. Six treatments were applied: 1. transrectal massage of the vesicular glands and the ampullary-prostate-urethral region for 3 min; 2. conventional electroejaculation; 3. intrarectal topical application of lidocaine followed by electroejaculation S min later; 4. epidural lidocaine anesthesia followed by electroejaculation 5 min later; 5. epidural xylazine anesthesia followed by electroejaculation 25 min later; and 6. light sedation with IV xylazine followed by electroejaculation S min later. A minimum of 48 h of sexual rest was allowed between treatments. Prior to all treatments, the rectum was evacuated of feces. The application of intrarectal topical lidocaine consisted of the introduction of 30 mL of lidocaine (2% Lidocaine HCI, 20 mg/mL, with epinephrine, 0.01 mg/mL, MTC Pharmaceuticals, Cambridge, Ontario) into the lumen of the rectum and its manual dispersal around the rectum. Epidural lidocaine anesthesia was achieved by injecting 6 mL of lidocaine into the epidural space at the 1st intercoccygeal space. Xylazine (Rompun, 20 mg/mL, Bayvet Division, Chemagro, Etobicoke, Ontario) was administered at 0.07 mg/kg body weight (BW) diluted in saline to a constant volume of 7 mL for epidural anesthesia or 0.033 mg/kg BW, IV, for sedation. The urethralis muscle, the ampulla of the ductus deferens, the prostate, and the vesicular glands were massaged transrectally for 3 min prior to the insertion of a 60-mm diameter probe with 3 ventrally oriented electrodes (Lane Manufacturing, Denver, Colorado, USA). The bulls were stimulated in an identical manner by using an electronic ejaculator (PRO-JAC IE Electronic Ejaculator, Protronics Professional Electronics, Falkland, British Columbia). Stimulation consisted of automatic pre-programmed 4-second-duration cycles (2 sec of stimulation followed by 2 sec of rest). Three stimulations were administered at each voltage increment. Voltage was manually advanced over 10 increments to a predetermined maximum voltage, which was known to cause ejaculation in most bulls. Each bull received the same maximum stimulation, regardless of whether or not ejaculation occurred. Baseline heart rate was determined prior to all treatments, immediately after treatment, and at 2-minute intervals after treatment for 10 min. A heart rate telemetry system (PARAGON 420 Cardiac Monitoring System, Quinton Instrument, Seattle, Washington, USA) was used for the remote recording of heart rate, to minimize disturbance of the animals during monitoring. Remote radio transmitters (TM8 Patient Transmitter, Quinton Instrument) were attached to the backs of the bulls by 8-cm long strips of Velcro, glued along the spine just caudal to the withers. One electrode of the transmitter was attached by an alligator clip to a surgical staple inserted into the skin on the left side, 8 to 10 cm caudal to the olecranon. The other electrode was attached in the same manner to a surgical staple inserted high up on the right side of the animal, at the caudal edge of the scapula. The staples were inserted 1 wk before the beginning of the experiment. The effect of treatments on rectal smooth muscle tone and the response to transrectal massage were determined by rectal palpation and visual observation. The Can Vet J Volume 39, August 1998

Table 1. Mean change in heart rate (beats per minute) immediately after treatment vs. pre-treatment. Heart rates are expressed at an average of 2 replicates of treatments administered to 3 bulls Treatment

Transrectal massageb Conventional

Pre-treatment Post-treatmenta Change in heart rate heart rate heart rate

63.9 61.6

79.8 83.1

15.9 21.5

66.0 71.3 52.9 55.5

87.8 85.7 62.1 69.1

21.8 14.4 9.2 13.6

electroejaculation Intrarectal lidocainec Epidural lidocaine Epidural xylazine Intravenous xylazine

aHeart rate immediately after treatment b'Transrectal massage of the vesicular glands and the ampullary-prostate-urethral region for 3 min c intrarectal topical application of lidocaine

strength and frequency of rectal peristalsis, pulsation of urethralis muscle, and the drawing of the testicles toward the abdomen were subjectively scored from 0 to 3 as 0 = no response, 1 = weak response, 2 = moderate/ diminished response, and 3 = strong/normal response. The effect of treatments on penile protrusion was scored by estimating the percentage of protrusion. The effect of treatments on seminal emission was scored as + or -. The treatments were done in random order, but each treatment was administered to all 3 bulls at the same time to prevent a day effect error. Measurements from the 2 replicates were averaged for each bull before analysis. The mean heart rates for each treatment are given in Table 1. Heart rate returned to baseline and remained at baseline in all bulls, for all treatments, within 2 min after treatment. Therefore, baseline heart rate and heart rate immediately after treatments were compared using a paired t-test of p(y - x). A Kruskal-Wallis one-way nonparametric ANOVA was used to compare the changes in heart rate in the various treatments against each other. The rapid return of heart rates to baseline after electroejaculation and the complete lack of aversion to entering the handling facilities after repeated electroejaculation may indicate that the pain due to electroejaculation in bulls is not severe. This is supported by these data in which there were no significant differences in heart rate change for any of the treatments (P > 0.05). However, there was a tendency for heart rates to be less elevated after some of the treatments. Heart rates immediately after treatment tended to be greater for conventional electroejaculation and electroejaculation with topical intrarectal lidocaine than for transrectal massage or electroejaculation with epidural lidocaine (P = 0.08). This may indicate that epidural lidocaine reduced pain due to electroejaculation. This would concur with the human experience in which epidural anesthesia is used to prevent pain during electroejaculation. However, caudal epidural anesthesia in animals may not be as effective in preventing pain as lumbosacral epidural anesthesia in humans. Furthermore, hindquarter muscle exertion appeared moderately diminished in bulls with epidural anesthesia and this alone may account for the reduced heart rate. Epidural or IV xylazine consistently resulted in copious salivation, transient bellowing, groaning, and laborious breathing within minutes of injection. Xylazinetreated bulls often laid down in the chute before or 505

after electrojacutCLll tioll .and displayed moderate to severe ataxia. Hindquarter- muscle exertion appeared moderately diminlished duLingLI electroejaculation in bulls aiven IV xylazine anid realtly diminished in those eiYven epidural xNlaine whell Compared with conventional electroejaIculation. Less Imuscle exertion anid the lower pretrei-atmiient heairt Lates caused by a pharmacological effect ot' xvlazine. as \well as reduced pain. inay account for the sma1.1ller incrcases, in healrat rate with xvlazine treatments comiipar-ed with coniventional electr-oejaculation. Hear-t rate changes afteCr electl-oejaculation tended to be lower for the epidul-rLl xIltaZine treatmnent thani for the IV xylazine or the epidLur-al lidocaine treatmenits. Thereftore. epidural Xvlaziine 11n11V be m1orec effective in preventing pain than either IV xvlazine or epidural lidocaine (Table 1) In addition. it appears unlikely that IV xvlazine is alny mole eeffective in preventing pain than is epidural licocaillne. EpidUral lidocailne and xylazine and IV xylazine resulted in (e.eatlv r-educed rectal smooth muscle contractions. Intrarectal lidocaine resulted in a moderate eCdLuCtiOnl in thle nulmliber and streneth of rectal smoaoth muLIscle Contractions land may ha-ve reduced rectal sensation. However, heaLr-t rate elevation for the intrarectal lidocaine treatmient was similar to that of conventional electroejaculation. indicating that pain during electroe,jaculation likel\ is not due to rectal smooth muscle spasm. Rather. it may be speculalted that pain from electroej.aculation'is due to strone nerve stimulation. Response to transrectal massaTe. as evidenced by the drawing up ol' the testicles. was not affected by the lidocaine treatmenlts: howvever. this response was diminished bv both xvliazine treatments. Urethralis muscle pulsations were greatly diiminished bv the epidural lidocaine treatmllent and by both xvlazine treatments. Tra n sr-ectal mnassaLe alone caused only partial penile protl-Lsion in all1 bullls aind did not cIuse semen emnission in anx' ot' the buLlls. Full penile protrusion and semnen emllissionI occUrred in all bulls with all of the other

tr-eaLtmlienlts. AlthougLL muscle exertion was not scored. hindquarterl- mLuscle exer-tioin during electroejaculation appeared

* Gravel impaction in a two-year-old Morgan gelding ( .i ro v ,Jc( BarborC ila 6 inc Bcllain v

* Effects of Tritrichomonas foetus and nutritional status on the fertility of cows on a community pasture in Saskatchewan. Raccl/l 1.1 Si cait Jo/lll R. Camipbell. Eii-enc 1). Lj(I1i'cil. la/In Ah1 Kinnon

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to be moderately diminished by epidural lidocaine and IV xvlazine. and greatly diminished by epidural xylazine. when compared wvith conventional electroejaculation. The data of this experiment are inadequate to draw any firm conclusions: however, it is our impression that caudal epidural anesthesia with lidocaine shows promise as a practical means to reduce pain during electroejaculation and more investication in this area may be warranted. Xylazine may not be practical for routine use in range bulls because of undesirable side effects. Since heart rate can be affected by muscle exertion as well as pain, it is not an ideal method for objectively measuring pain response. However, at this time, no other methods, including the use of hormonal assays. have been identified that can reliably differentiate between mild or (CV severe stress or pain.

References 1. Stflttor-d KJ. ElectrocjaLCulaltionl: at Welfare issue? Surveillance 1995: ": 15-17. 2. Ohl DA-\. ElectrocjacUlatioll. U-rol Cliii of North Am 1993: 2): 181-188. 3. Catrter PD. Hamiltoni PA. DLIff\ JH. ElectroejaZCulaZtion in gLoats. AuLst Vet J19: 367:91-93. 4. Barth AD. Bowman PA. Thc sequential appearance of sperm ahnormall ties aifter sci-otail iIsLIlatioli or dexamiiethasonie treatmiienit in buLlls. Canl Vet J: 1994: 35: 93-12P 5 Alamn NIGS. Dobso H. Ettect of various veterinarv procedures on plasmiia conicenitrationis ot cortisol. .uteinizing hormone and prostagLlandin F2cY metaibolite in the cow. Vet Rec 1986: 118: 7-10. f. Mellor DJ. Nlurrav L. Ettects of tail dockin- and castration oi behav ior atnd plasmaz cor-tisol concenitrations in VouLng l.ambs. Res Vet Sci 1989: 46: 387-391. 7. Shutt DA. Fell LR. Conniell R. Bell AK. Wallalce CA. Smith Al. Stress-iniduced changes in plasmia concentr-ations of imrnunoreactive betai-enidorphin aiid col-tisol in response to routille surgical procedulres in lamiibs. Aust J Biol Sci 1987: 41): 97-103. 8. Shutt DA. Fell LR. Conllell R. Bell AK. Stress responises in lambs docked and castraited surgically or by the aipplication of -uLbber- rinns AsIt Vet J 1988: 65: 5-7. 9. Cooper C. EvaIns ACO. Cook S. Rawlings NC. Cortisol. pro-esteronie and 13-endorphin responise to stress in calves. Can J Anim Sci 1995 95: 197-201. 10. Welsh TH Jr.. Johnison BH. Stress-induced ailteraitionis in secretion of corticosteroids. progesterone. luteinizing hormone. and testoster-onie in bulls. Endocri noloes 1 98 1: 109: 85-19(1.

* A redefined type of elbow dysplasia in the dog -2 cases Tainara M. at'olker-

* Osteochondritis dessicans and subchondral cystic lesions in draft horses: A retrospective study Christophler B. Rilev IV. Micth1ael Stott, Jo/llz P. Calronl, Pete- B. Fi-tziL Jcve-e2la V. Balev. S.M. Barzber

Can Vet J Volume 39, August 1998