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  • 1. y A r t i c l e #6 ( 1 . 5 c o n t a c t h o u r s ) Refereed Peer Review Effects of Musculoskeletal and neurologic Musculoskeletal and diseases, which are important causes of poor breeding performance in stallions, can Neurologic Diseases on be recognized and treated to prolong the stallion’ breeding career. s Breeding Performance in Stallions musculoskeletal and neurologic University of Pennsylvania systems as a common primary cause of poor breeding Benson B. Martin, Jr., VMD performance is crucial to Sue M. McDonnell, PhD successful evaluation and Charles C. Love, DVM, PhD therapy, p. 1160. 1 The most important steps in L ibido, mounting, thrusting, and ejaculatory dysfunctions represent ma- treating chronic back pain are to 1,2 jor causes of poor breeding performance in stallions. Musculoskeletal determine and treat the primary 2 and neurologic diseases account for up to 50% of these problems. The cause, p. 1162. stallion breeding soundness examination (BSE) does not routinely include a complete musculoskeletal and neurologic examination,3,4 and in our experience Ill The importance of weekly these systems are often overlooked when evaluating subfertile stallions. This ar- monitoring and the use of a ticle describes evaluation and therapy for stallions with poor breeding perfor- good farrier for stallions with mance and summarizes findings in 25 horses presented for routine BSEs or for chronic laminitis cannot be evaluation of specific libido or ejaculatory dysfunction for which musculoskele- overemphasized, p. 1163. tal or neurologic disease was found to be the primary cause or a significant as- sociated factor. u Poor performance in breeding stallions is typically multifactorial DIAGNOSTIC APPROACH and may involve the History musculoskeletal, neurologic, and A complete history includes signalment, performance career, duration and de- reproductive systems; behavior tails of breeding experience, presenting problem and associated details, medical can also be a factor, p. 1166. history, medication, and nutrition. Information about the environment (includ- ing housing and breeding facilities [e.g., flooring, phantom]) and breeding pro- tocol (semen collection technique, stallion handling) should also be collected. Breeding Soundness Examination The routine BSE includes general physical examination, examination of the
  • 2. internal and external genitalia, -I_ suggesting discomfort or evaluation of at least two ejac- FJ- distraction; failure to grasp ulates collected 1 hour apart, J - securely with the forelimbs; and evaluation of penile mi- .’ lateral instability; falling croflora. The procedure has during thrusting or dis- been outlined by the Society +I -. . . ‘ ) . mount; weak, thready, 4 of Theriogenology. or irregular ejaculatory pulses (often variable from Basic Lameness and :;-, - day to day); and fore- or Neurologic Examinations hindlimb lameness after 2 Lameness and neurologic ex- breeding. Other com- aminations are performed as mon manifestations of described in Complete Muscu- -I- musculoskeletal pain in- loskeletal and Neurologic Ex- Figure 1A clude reluctance to mount 5-7 amination. It is useful to ob- or dismount, early dis- serve the horse for lameness mount, squealing during and neurologic signs while it is dismount, or savaging the being teased and particularly mare or handler during or during mounting, thrusting, immediately after mount- and dismount. Specific find- ing (see Differential Diag- ings that are suggestive of a noses of Musculoskeletal musculoskeletal or neurologic Pain). problem include failure to couple squarely (Figure 1) and Additional thrust with a smooth, rhyth- Examinations mic pelvic action; asymmetric Based on the combined hindlimb weight bearing and, findings of the examina- thrusting; failure to properly Figure 1B tions described above, flex or use the neck and/or Figure 1-(A) Good and (B) poor coupling positions. additional tests may be _____________--_________________________------ back; abnormal tail posture; indicated. For example, anxious look in the eyes and/or atypical ear postures frame-by-frame analysis of videotaped breeding behav- Basic Lameness Examination Walking uphill and downhill Examination of front feet using hoof testers Placing examination (i.e., place one front or hind foot Flexion of front fetlocks and carpi at rest in front of the other and observe whether the horse Palpation of neck, back, and gluteal muscles re-places its foot normally) Hock flexion and hind fetlock flexion at rest Additional Diagnostic Tests Walk and trot in-hand Ultrasonographic evaluation of the pelvic genitalia Repeat flexion tests at a trot and aorta sic Neurologic Examination Hematology for creatinine phosphokinase (0 and 30 Overall muscular symmetry minutes postbreeding) Facial nerves Radiography Flexion and extension of neck Cerebrospinal fluid and serum evaluation for equine Circumduction while circling to left and right protozoal myeloencephalitis titers Walking a serpentine path Scintigraphy Tail-pull test to left and right Nerve blocking Backing and stopping Video analysis of breeding behavior NEUROLOGIC FINDINGS n MUSCULOSKELETAL PROBLEMS n COUPLING POSITIONS
  • 3. ior can often provide useful Medical Management insight into the specific area of Musculoskeletal of pain or discomfort and Disease can help to identify han- Sore front or hind feet, including foot abscesses Degenerative dling factors that enhance or Laminitis Joint Disease impair performance. Ultra- The most common drugs sonographic evaluation of Degenerative joint disease (fetlocks, carpi, stifles, used in the medical manage- the pelvic aorta is useful in hocks) ment of pain in horses are cases of hindlimb weakness Forelimb abrasions (carpal rub sores) nonsteroidal antiinflammato- 9 and pain. Aortoiliac throm- Sore shoulder ry drugs (NSAIDs; Table 1). bosis, which results in libi- Sore neck We recommend initial treat- do, erection, and/or cjacula- ment with oral phenylbuta- Cervical vertebral malformation tory dysfunction in breeding zone (tablet, paste, or granu- 8 stallions, manifests as de- Equine protozoal myeloencephalitis lar form; 1.5 to 2 g twice layed ejaculation (multiple Sore back daily for 4 to 5 days, then mounts and more than 12 Sore gluteals titrated to 1 g twice daily for thrusts); progressive hind- Aortoiliac thrombosis (hindlimb weakness, pain) an additional 5 to 7 days), limb weakness and/or pain Hindlimb weakness which should be accompa- during thrusting resulting in nied by a period of sexual Nerve root injury “camping under” the mare and general rest if possible. In or phantom; and difficulty Myopathy our experience this has been backing up to dismount. the most effective pain treat- Erection aberrations can in- ment, although improvement clude delayed or rapid tume- may not be immediate. If the scence or detumescence or treatrnent is helpful, the stal- loss of erection during thrust- lion can continue receiving ing. Dose a Route Frequency low doses of phenylbutazone without it having a measur- THERAPEUTIC Phenylbutazone 2.2 PO, IV BID able effect on sperm produc- STRATEGIES Flunixin meglumine 1.1 IV, IM BID 10 tion or testicular size. Treat- Our general approach in- ed horses should be monitored Ketoprofen 1.1 IV SID volves formulating a specific for signs of phenylbutazone Aspirin 15-100 PO SID toxicity, including colic, loss plan, including pharmaco- logic therapy, acupuncture, Isoxsuprine 1.2 PO BID of appetite, diarrhea, depen- corrective shoeing, changes Methocarbamol 40 PO BID dent edema and mucosal ul- 11 in breeding management, Sulfamethoxazole 12.5 PO BID ceration, or renal disease. specific behavior modifica- Sulfadiazine 12.5 PO BID On occasion, another type of tion, and other management Pyrimethamine 1 PO SID NSAID (e.g., ketoprofen) details such as exercise and Folate 0.5 PO SID may be helpful; flunixin nutrition. Our experience Vitamin E 5000 IU PO SID meglumine and ketoprofen indicates that therapy is Polysulfated Variable IM Variable are also commonly used for most likely to succeed when glycosaminoglycans initial treatment. Intraarticu- all options are considered lar medications such as corti- Hyaluronic acid Variable IA, IV Variable and implemented simulta- costeroids, polysulfated gly- Glucosamine and Variable PO’0 Variable neously rather than individ- cosaminoglycans (Adequan®, purified chondroitin Luitpold Pharmaceuticals), ually. Other factors that must be taken into account sulfate or hyaluronic acid (Hylartin- include the history, breeding aUnless specified, doses are in mg/kg. V®,‘, Luitpold Pharmaceuti- farm conditions, and avail- BID = twice daily; IA = intraarticular; IM = intramuscular; IV= cals) are useful in the man- ability of veterinary care. intravenous; PO = oral; SID = once daily. agement of degenerative joint We generally include spe- disease; polysulfated gly- cialists in the fields of sports medicine, reproduction, cosarninoglycans and hyaluronic acid (Legend®, Bayer) and behavior in the planning process. can also be administered intramuscularly and intra- AORTOILIAC THROMBOSIS n THERAPY PLAN n PHENYLBUTAZONE
  • 4. venously, respectively. In addition, an oral preparation of have poor lateral stability. A mount mare that does not glucosamine combined with purified chondroirin sulfate wiggle side-to-side is usually best for collecting semen (Cosequin®, Nutramax Laboratories) may be used. from such stallions. If the mare does move side-to-side, providing lateral support at the stallion’ hips can be s Chronic Back Pain helpful. A dummy mount may be better in these cases The most important steps in treating chronic back pain but typically elicits less vigorous thrusting than does a are to determine and treat the primary cause. Pain can be live mount mare. secondary to another musculoskeletal cause, a heavy breed- ing schedule, poor footing, poor shoeing, or some other Cervical Vertebral Malformation problem that can be remedied. Chronic back pain may be Treatment of cervical vertebral malformation in adult best treated using acupuncture once weekly for 8 weeks and horses can be challenging, and horses that undergo 12 5 then every 3 to 4 weeks or as needed. Acupuncture thera- surgery may not be usable for several months. Medical 12,13‘ py may be combined with NSAID administration. -’ treatment includes acupuncture and NSAIDs for allevi- ation of pain associated with breeding (Table 1). Proper Laminitis management is extremely important and includes good Although shoeing and trimming are important in the footing, proper shoeing, proper positioning of the mare treatment of chronic laminitis, medication (phenylbu- or phantom, ground cotlecrion of semen, and pharma- 1,3 tazone, flunixin meglumine, isoxsuprine, and aspirin) can cologic aids to ejaculation when necessary. 14 also be useful in managing its associated pain. In addi- tion to alleviating pain, aspirin may help prevent further Equine Protozoal Myeloencephalitis thrombus formation; its relatively short half-life in rhe The management of horses with equine protozoal horse is its only drawback.11 Treatment for chronic pain myeloencephutiris (EPM) is similar to that for cervical in horses has also included electroacupuncture, particular- vertebral malformation; however, medical management 15,16 ly in refractory cases. includes the use of pyrimethamine and sulfadiazine or sulfamethoxazole administered on a daily basis for at Myositis 18 least 60 to 90 days (Table 1). An occasional side effect 18 Myositis, evidenced by lameness, pain, sweating, firm associated with this therapy is anemia. Accordingly, muscles, and markedly increased serum creatinine ki- daily oral administration of a folate supplement and vi- 18 nase activities, can be the primary cause of poor breed- tamin E is advised. Recent work indicates this treat- 19 ing performance. For horses that have acute myositis ment does not significantly affect sperm production. accompanied by colic, anxious sweating, and very firm muscles in conjunction with increased serum muscle Management and Pharmacologic enzymes, it may be useful to 1) administer aceproma- Aids to Ejaculation zine (10 to 20 mg) intravenously to control anxiety; 2) In general, management goals are to enhance sexual administer balanced electrolyte solution (10 to 20 L) arousal, reduce any pain, accommodate musculoskeletal 1 intravenously; 3) keep the horse confined to a stall; and deficiencies, and maximize penile sensation (see Man- 4) monitor its progress until the crisis is over. Metho- agement and Pharmacologic Aids to Facilitate Ejacula- carbamol may also be helpful in selected cases (Table 1). tion). The management aids listed are simple, inexpen- For horses with chronic myositis, it may be better to al- sive, and easily implemented in most situations. They ter the diet to include low-quality hay and a reduced do require some client education in terms of develop- volume of high-carbohydrate feed; such horses should ing patience and good stallion handling skills. Pharma- be placed on a diet consisting primarily of hay and cologic aids are aimed at boosting sexual arousal and high-quality, low-protein, low-carbohydrate feed. - lowering the ejaculatory threshold at the level of the genital smooth muscle. Medical Management of Neurologic Disease Foot care is an important consideration in breeding Breeding management of stallions with neurologic stallions with musculoskeletal or neurologic problems. disease can be successful, but special precautions must Some stallions will benefit greatly from corrective trim- be taken during collection of semen or breeding to pro- ming and shoeing. It may be advisable to allow stallions tect the stallion, the mare, and the personnel working that are unstable during mounting and thrusting to be around the stallion. It is particularly important to have left unshod to minimize the risk of injury to the mare, adequate footing and to ensure that the mare or phan- stallion (stepping on his pasterns or heels), and person- tom is properly positioned to lessen the risk of the stal- nel. We recommend examining the feet at least every 4 lion falling. Stallions with neurologic disease typically to 6 weeks to ensure that they are in balance and shod PAIN MANAGEMENT H BREEDING MANAGEMENT n FOOT CARE
  • 5. havior is sometimes mistak- The most common medi- enly assumed to be the cause cal treatment was NSAIDs of poor breeding perfor- (88%), followed by acu- mance and is punished. Re- puncture (24%) and correc- suiting penile injury and/or tive shoeing (12%). Special psychologic inhibition of breeding management tech- erection may exacerbate niques (92%) and adminis- poor breeding performance. tration of drugs to induce ejaculation (32%) were the SUMMARY OF CASES most common management We recently reviewed the techniques employed and case histories of 25 breeding were necessary only during stallions that were presented the crisis or intermittently to the Widener Hospital, thereafter in most cases. Spe- University of Pennsylvania, cial management techniques School of Veterinary Medi- were continued indefinitely) cine, New Bolton Center in six horses (28%). between 1987 and 1998; Twenty-three (92%) of Figure 2A the horses were presented these stallions were success- for either routine BSEs or fully returned to breeding, for evaluation of specific and 21 of these were still libido or ejaculatory dys- breeding successfully 2 years function for which musculo- later. The remaining two loskeletal or neurologic dis- stallions were successfully ease was the primary cause completing the 1998 season or a significant associated when this article was written. factor. A variety of breeds As mentioned, three stal- and performance types were lions had laminitis. Stallions included; horses ranged in with this condition can typi- age from 3 to 19 years, and cally continue breeding but all but one were experienced require special attention to breeders. The duration of their weight, trimming, and poor hreeding performance shoeing. Their breeding per- ranged from less than 1 year formance can be expected to to more than 10 years. Ejac- wax and wane with the epi- ulatory dysfunction was the sodes of laminitis. primary problem in 24 of I Aortoiliac thrombosis was the stallions; the other horse’s primary problem was intermittent failing dur- Figure 2B two stallions. Both are Stan- ing breeding. Additional Figure 2-Stabilizing (A) the artificial vagina and (B) the hips dardbreds with full books of problems included falling to stop a stallion from advancing up the side of a dummy mares by artificial insemina- from the dummy during -----__-____^__________l________l__l____-----~ mount. tion. They continue to be dismount (three stallions), successfully managed (for reduced libido (nine stal- several years now) using a lions), and recurrent urospermia (two stallions). combination of controlled daily exercise to stimulate The most common musculoskeletal findings were collateral circulation, proper positioning of the mare, sore back (84%), lameness (64%), degenerative joint collection of semen under ideal conditions, a thrice- disease (40%), lameness after breeding (25%), myositis weekly breeding schedule, phenylbutazone to maintain (12%; creatinine kinase range, 1000 to 44,000 IU/L [± comfortable breeding, and use of pharmacologic aids to 17,000]), and laminitis (12%). Aortoiliac thrombosis, ejaculation (gonadotropin-releasing hormone, imip- 8,20 cervical vertebral malformation, and EPM were diag- ramine) when needed. nosed in 24%, 8%, and 4% of cases, respectively. Six stallions had cervical vertebral malformation, and EJACULATORY DYSFUNCTION R SORE BACK n LAMINITIS
  • 6. three of these had markedly greater difficulty breeding my by having an assistant put gentle pressure on the immediately after being exercised. They all experienced hips of the horse (Figure 2B). an apparent worsening of their condition with each Management changes that did not address the prima- subsequent breeding season and typically required pro- ry musculoskeletal or neurologic problem appeared to gressively greater assistance to continue breeding, de- complicate and worsen the problem in several other pending on the nature of rhe cause and the degree of cases. For example, extremely vigorous manipulation of recovery. the artificial vagina in an attempt to stimulate ejacula- One horse was diagnosed with EPM, which appeared tion in one stallion (whose primary problem was most to stabilize with complete or nearly complete allevia- likely a sore back) created the additional complicating tion of clinical signs. The subsequent breeding season problems of penile and stifle abrasions and scrotal ede- proceeded with normal breeding behavior, semen quali- ma. ty, and fertility. Several of the stallions were obese and unfit. Man- In several of these cases, a musculoskeletal problem agers typically further restricted exercise as breeding was judged to be primarily manmade. For example, the problems developed on the assumption that the horse first episode of falling during breeding for one stallion needed rest. was associated with a change in dummy cover and foot- An interesting observation in two Quarter Horse stal- ing around the dummy. Four stallions had sore backs as lions in this clinical population was the complicating a result of improper positioning on the dummy mount; factor of sore front and hind feet in association with in all cases the stallion was allowed to advance up the undersized shoes designed to fashion small feet. We rec- side of the dummy mount during breeding so that its ommended that these stallions be either shod full or back was markedly curved during thrusting. Also, in left unshod, which markedly improved breeding perfor- each of these cases an extra long dummy was made mance. specifically to accommodate this behavior. The habit was immediately and easily corrected by positioning the CONCLUSION artificial vagina against the dummy at the rear (Figure A reasonable percentage of cases of poor breeding 2A) and keeping the stallion squarely behind the dum- performance can be attributed to primary muscu- loskeletal or neurologic causes. Such stallions are often presented for or with additional signs of psychologic sexual behavior dysfunction. In our experience, these signs often confound the evaluation and diagnosis of primary physical causes of poor breeding performance. Sorting out other components, such as stallion inexpe- rience, footing, artificial vagina conditions, dummy mount, or mare factors, is often difficult. Most of the stallions diagnosed with and treated for musculoskeletal problems typically can maintain adequate performance for many years with well-designed management plans 1,2,10,17,21,26 and minimal medication. A team approach to the evaluation and therapy for these horses is successful and time- and cost-efficient. The professional fees for evaluation and therapy of this population of referral cases at our facility was typically less than $700, which is less than a single breeding fee for most of the stal- lions. Many of rhe musculoskeletal and neurologic prob- lems represented in this clinical population were not immediately evident on traditional lameness examina- tion alone. Therefore it is our opinion that examination during breeding is important when evaluating poor breeding performance in stallions. If the clinician is in- experienced or feels uncomfortable performing such an evaluation, the services of a breeding specialist (either through an on-farm consultation or evaluation of a IMPROPER MOUNTING POSITION @ UNDERSIZED SHOES
  • 7. videotape of the stallion during breeding) can be in- tis. Vet Clin North Am Equine Pract3(2):397-404, 1987. ‘lin valuable. Although a primary physical cause of poor 7. Blythe LL: Neurologic examination of the horse. Vet Clin breeding performance may be identified, it is important North Am Equine Pat 3(2):255-282, 1987. rc 8. McDonnell SM, Love CC, Martin BB, Reef VB: Ejaculatory to remember that successful therapy usually requires failure associated with aortic-iliac thrombosis in 2 stallions. treatment of the secondary psychologic component of JAVMA 200(7):954-957, 1992. the problem. 9. Robinson NE: Appendices, in Robinson NE (ed): Current Repeated examinations before and after breeding Therapy in Equine Medicine, ed 3. Philadelphia, WB Saun- and before and after a course of analgesics are often ders Co, 1992, pp 8 15-821. useful. Once a treatment is determined to be effec- 10. McDonnell SM, Love CC, Pozor MA, Diehl NK: Phenyl- tive, it is advisable to wean the medication to the butazone treatment in breeding stallions: Preliminary evi- least effective dose to minimize the risk of side ef- dence for no effect on semen or testicular size. Theriogenology fects. 37: 1225-1232, 1992. 11. Mitten LA, Hinchcliff KW: Nonsteroidal anti-inflammatory In summary, poor breeding performance in stallions drugs, in Robinson N (ed): Current Therapy in Equine often represents a combination of musculoskeletal, Medicine, ed 4. Philadelphia, WB Saunders Co, 1997, pp neurologic, behavioral, and management factors. A 724-727. common theme in the history of affected stallions is 12. Martin BB, Klide AM: Diagnosis and treatment of chronic treatment of selected factors with no or limited suc- back pain in horses. ProcAAEP43:310-312,1997. cess, often for a period of years. It is our opinion that 13. Martin BB, Klide AM: Acupuncture for treatment of chron- successful evaluation and treatment include simultane- ic back pain in horses. Veterinary Acupuncture: Ancient Art to ously recognizing and addressing all of these compo- Modern Medicine. Goleta, Ca, American Veterinary Publica- nents. tions, 1994, pp 533-542. 14. Goetz TM: Treatment of chronic laminitis in horses. Vet Clin North Am Equine Pract 5( 1):73-108, 1989. ACKNOWLEDGMENTS 15. Klide AM: Acupuncture for the treatment of chronic lamini- Drs. Regina Turner, Patricia Sertich, Margo tis in the horse, in Proc it Vet Acup Soc Corzg on Vet Acup nl Macpherson, Eric Twitchell, Nancy Diehl, Virginia 16/1-16/3, 1990. Reef, Malgorzata Pozor, and Sylvia Bedford participat- 16. Steiss JE, White NA, Bowen JM: Electroacupuncture in the ed in one or more of these cases. treatment of chronic lameness in horses and ponies. Can J Vet Res 53(2):239-243, 1989. 17. Beech J: Rhabdomyolysis (tying up) in Standardbred and About the Author Thoroughbred racehorses. Intl Equine Neuro Cony, 1997, pp Dr. Martin is affiliated with the Section of Sports Medicine 79-80. 18. Fengar CK: Equine protozoa1 myeloencephalitis. Compend and Imaging and Dr. McDonnell is with the Section of Re- Contin Educ Pract Vet 19(4):513-534, 1997. production and Medicine, School of Veterinary Medicine, 19. Bedford SJ, McDonnell SM: Semen, testicular volume, University of Pennsylvania, Kennett Square, Pennsylva- sperm production efficiency, and sexual behavior of stallions nia. Dr. Love is currently living in Webster Groves, Mis- with trimethoprim-sulfamethoxazole and pyrimethamine. souri; at the time the article was written, he was affiliated To be presented at the 44th Annual AAEP Convention, De- with the Section of Reproduction and Medicine, School of cember 1998. Veterinary Medicine, University of Pennsylvania, Kennett 20. McDonnell SM, Love CC: Xylazine induced ex copula ejac- Square, Pennsylvania. ulation in stallions. Theriogenology 36(1):73-76, 1991. 2 1. Oristaglio-Turner RM, Love CC, McDonnell SM, et al: Use of imiprimine hydrochloride for treatment of urospermia in a stallion with a dysfunctional bladder. JAVMA 207( 12): REFERENCES 1602-1606, 1995. 1. McDonnell SM: Normal and abnormal sexual behavior. Vet 22. McDonnell SM, Pozor MA, Beech J, Sweeney RW: Use of Clin North Am Equine Pract8(1):71-89, 1992. 2. McDonnell SM: Ejaculation physiology and dysfunction. manual stimulation for collection of semen from an atactic Vet Clin North Am Equine Pract 8(1):57-70, 1992. stallion unable to mount. JAVMA 199(6):753-754, 1991. 3. Love CL: Semen collection techniques. Vet Clin North Am 2.3. McDonnell SM, Oristaglio-Turner RM: Post-thaw motility Equine Pract 8(1):111-128 1992. and longevity of motility of imiprimine-induced ejaculates 4. Kenney RM : Clinical Fertility Evaluation of the Stallion of pony stallions. Theriogenology‘ 42:475-481, 1994. g Hastings, Nebraska, The Society for Theriogenology, 1983. 24. McDonnell SM, Love CC: Manual stimulation collection of 5. Wagner PC, Grant BD, Reed SN: Congenital vertehral mal- semen from stallions: Training time, sexual behavior, and se- formation. V e t Clin North Am Equine Pract 3(2)385-392, men. Theriogenology 33(6):1203-1210, 1990. 1987. 25. McDonnell SM, Garcia MC, Kennry RM: imipramine-in- 6. Madigan JE, Higgins RT: Equine protozoa1 myeloencephali- duced erection, masturbation, and ejaculation in male hors-
  • 8. es. Pharmacol Biochem Behav 27: 187-191, 1987. 26. Crump J, Crump J: Stallion ejaculation induced by manual stimulation of the penis. Theriogenology 3 1(2):341-346, 1989.

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