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• Early Spay-Neuter Considerations for the Canine Athlete
One Veterinarian's Opinion, © 2005 Chris Zink DVM, PhD, DACVP

Those of us with responsibility for the health of canine athletes need to continually read and evaluate new scientific studies to ensure that we are taking the most appropriate care of our performance dogs. This article provides evidence through a number of recent studies to suggest that veterinarians and owners working with canine athletes should revisit the standard protocol in which all dogs that are not intended for breeding are spayed and neutered at or before 6 months of age.
Orthopedic Considerations
A study by Salmeri et al in 1991 found that bitches spayed at 7 weeks grew significantly taller than those spayed at 7 months, who were taller than those not spayed (or presumably spayed after the growth plates had closed).(1) A study of 1444 Golden Retrievers performed in 1998 and 1999 also found bitches and dogs spayed and neutered at less than a year of age were significantly taller than those spayed or neutered at more than a year of age.(2) The sex hormones, by communicating with a number of other growth-related hormones, promote the closure of the growth plates at puberty (3), so the bones of dogs or bitches neutered or spayed before puberty continue to grow. Dogs that have been spayed or neutered well before puberty can frequently be identified by their longer limbs, lighter bone structure, narrow chests and narrow skulls. This abnormal growth frequently results in significant alterations in body proportions and particularly the lengths (and therefore weights) of certain bones relative to others. For example, if the femur has achieved its genetically determined normal length at 8 months when a dog gets spayed or neutered, but the tibia, which normally stops growing at 12 to 14 months of age continues to grow, then an abnormal angle may develop at the stifle. In addition, with the extra growth, the lower leg below the stifle likely becomes heavier (because it is longer), and may cause increased stresses on the cranial cruciate ligament. In addition, sex hormones are critical for achieving peak bone density.(4) These structural and physiological alterations may be the reason why at least one recent study showed that spayed and neutered dogs had a higher incidence of CCL rupture.(5) Another recent study showed that dogs spayed or neutered before 5 1/2 months had a significantly higher incidence of hip dysplasia than those spayed or neutered after 5 1/2 months of age, although it should be noted that in this study there were no standard criteria for the diagnosis of hip dysplasia.(6) Nonetheless, breeders of purebred dogs should be cognizant of these studies and should consider whether or not pups they bred were spayed or neutered when considering breeding decisions.
Cancer Considerations
A retrospective study of cardiac tumors in dogs showed that there was a 5 times greater risk of hemangiosarcoma, one of the three most common cancers in dogs, in spayed bitches than intact bitches and a 2.4 times greater risk of hemangiosarcoma in neutered dogs as compared to intact males.(7) A study of 3218 dogs demonstrated that dogs that were neutered before a year of age had a significantly increased chance of developing bone cancer.(8) A separate study showed that neutered dogs had a two-fold higher risk of developing bone cancer.(9) Despite the common belief that neutering dogs helps prevent prostate cancer, at least one study suggests that neutering provides no benefit.(10) There certainly is evidence of a slightly increased risk of mammary cancer in female dogs after one heat cycle, and for increased risk with each subsequent heat. While about 30 % of mammary cancers are malignant, as in humans, when caught and surgically removed early the prognosis is very good.(12) Luckily, canine athletes are handled frequently and generally receive prompt veterinary care.
Behavioral Considerations
The study that identified a higher incidence of cranial cruciate ligament rupture in spayed or neutered dogs also identified an increased incidence of sexual behaviors in males and females that were neutered early.(5) Further, the study that identified a higher incidence of hip dysplasia in dogs neutered or spayed before 5 1/2 months also showed that early age gonadectomy was associated with an increased incidence of noise phobias and undesirable sexual behaviors.(6) A recent report of the American Kennel Club Canine Health Foundation reported significantly more behavioral problems in spayed and neutered bitches and dogs. The most commonly observed behavioral problem in spayed females was fearful behavior and the most common problem in males was aggression.(12)
Other Health Considerations
A number of studies have shown that there is an increase in the incidence of female urinary incontinence in dogs spayed early (13), although this finding has not been universal. Certainly there is evidence that ovarian hormones are critical for maintenance of genital tissue structure and contractility.(14, 15) Neutering also has been associated with an increased likelihood of urethral sphincter incontinence in males.(16) This problem is an inconvenience, and not usually life-threatening, but nonetheless one that requires the dog to be medicated for life. A health survey of several thousand Golden Retrievers showed that spayed or neutered dogs were more likely to develop hypothyroidism.(2) This study is consistent with the results of another study in which neutering and spaying was determined to be the most significant gender-associated risk factor for development of hypothyroidism.(17) Infectious diseases were more common in dogs that were spayed or neutered at 24 weeks or less as opposed to those undergoing gonadectomy at more than 24 weeks.(18) Finally, the AKC-CHF report demonstrated a higher incidence of adverse reactions to vaccines in neutered dogs as compared to intact.(12)

I have gathered these studies to show that our practice of routinely spaying or neutering every dog at or before the age of 6 months is not a black-and-white issue. Clearly more studies need to be done to evaluate the effects of prepubertal spaying and neutering, particularly in canine athletes.
Currently, I have significant concerns with spaying or neutering canine athletes before puberty. But of course, there is the pet overpopulation problem. How can we prevent the production of unwanted dogs while still leaving the gonads to produce the hormones that are so important to canine growth and development? One answer would be to perform vasectomies in males and tubal ligation in females, to be followed after maturity by ovariohysterectomy in females to prevent mammary cancer and pyometra. One possible disadvantage is that vasectomy does not prevent some unwanted behaviors associated with males such as marking and humping. On the other hand, females and neutered males frequently participate in these behaviors too. Really, training is the best solution for these issues. Another possible disadvantage is finding a veterinarian who is experienced in performing these procedures. Nonetheless, some do, and if the procedures were in greater demand, more veterinarians would learn them.
I believe it is important that we assess each situation individually. For canine athletes, I currently recommend that dogs and bitches be spayed or neutered after 14 months of age.
References:
1. Salmeri KR, Bloomberg MS, Scruggs SL, Shille V.. Gonadectomy in immature dogs: effects on skeletal, physical, and behavioral development. JAVMA 1991;198:1193-1203
2. http://www.grca.org/healthsurvey.pdf
3. Grumbach MM. Estrogen, bone, growth and sex: a sea change in conventional wisdom. J Pediatr Endocrinol Metab. 2000;13 Suppl 6:1439-55.
4. Gilsanz V, Roe TF, Gibbens DT, Schulz EE, Carlson ME, Gonzalez O, Boechat MI. Effect of sex steroids on peak bone density of growing rabbits. Am J Physiol. 1988 Oct;255(4 Pt 1):E416-21.
5. Slauterbeck JR, Pankratz K, Xu KT, Bozeman SC, Hardy DM. Canine ovariohysterectomy and orchiectomy increases the prevalence of ACL injury. Clin Orthop Relat Res. 2004 Dec;(429):301-5.
6. Spain CV, Scarlett JM, Houpt KA. Long-term risks and benefits of early-age gonadectomy in dogs. JAVMA 2004;224:380-387.
7. Ware WA, Hopper DL. Cardiac tumors in dogs: 1982-1995. J Vet Intern Med 1999 Mar-Apr;13(2):95-103
8. Cooley DM, Beranek BC, Schlittler DL, Glickman NW, Glickman LT, Waters D, Cancer Epidemiol Biomarkers Prev. 2002 Nov;11(11):1434-40
9. Ru G, Terracini B, Glickman LT. Host related risk factors for canine osteosarcoma. Vet J. 1998 Jul;156(1):31-9.
10. Obradovich J, Walshaw R, Goullaud E. The influence of castration on the development of prostatic carcinoma in the dog. 43 cases (1978-1985). J Vet Intern Med 1987 Oct-Dec;1(4):183-7
11. http://www.akcchf.org/pdfs/whitepapers/Biennial_National_Parent_Club_Canine_Health_Conference.pdf
12. Meuten DJ. Tumors in Domestic Animals. 4th Edn. Iowa State Press, Blackwell Publishing Company, Ames, Iowa, p. 575
13. Stocklin-Gautschi NM, Hassig M, Reichler IM, Hubler M, Arnold S. The relationship of urinary incontinence to early spaying in bitches. J. Reprod. Fertil. Suppl. 57:233-6, 2001
14. Pessina MA, Hoyt RF Jr, Goldstein I, Traish AM. Differential effects of estradiol, progesterone, and testosterone on vaginal structural integrity. Endocrinology. 2006 Jan;147(1):61-9.
15. Kim NN, Min K, Pessina MA, Munarriz R, Goldstein I, Traish AM. Effects of ovariectomy and steroid hormones on vaginal smooth muscle contractility. Int J Impot Res. 2004 Feb;16(1):43-50.
16. Aaron A, Eggleton K, Power C, Holt PE. Urethral sphincter mechanism incompetence in male dogs: a retrospective analysis of 54 cases. Vet Rec. 139:542-6, 1996
17. Panciera DL. Hypothyroidism in dogs: 66 cases (1987-1992). J. Am. Vet. Med. Assoc., 204:761-7 1994
18. Howe LM, Slater MR, Boothe HW, Hobson HP, Holcom JL, Spann AC. Long-term outcome of gonadectomy performed at an early age or traditional age in dogs. J Am Vet Med Assoc. 2001 Jan 15;218(2):217-21.
This article is available for download in Adobe Acrobat PDF format Early Spay Considerations (pdf)

• DEW CLAWS, With A Flick of the Wrist by Chris Zink, DVM, PhD (as seen in Dogs In Canada – September 2003)
In the hundreds of agility trials I have attended over the years, only rarely have I seen a dog suffer an acute, serious injury. An exception happened in early May this year. I was relaxing at ringside, enjoying one of the rare rain free moments this spring offered, watching a bi-black Sheltie named 'Shadow' negotiate the Open Jumpers course with smooth abandon. Suddenly the dog took a misstep, completely misjudged where he should take off, and crashed into the jump. As he fell, his front legs landed on the fallen jump bars, and he immediately let out an agonized scream. He was still crying as he was carried out of the ring. I ran over to help and examined the dog in a shady area some distance from the ring.
Shadow's left front leg was extremely painful and he held it stiffly away from his body. In a few minutes he had relaxed enough for me to determine that there were no major bone breaks. In fact, the main problem appeared to be a severe sprain of the carpus (wrist). Later X-rays not only confirmed my finding, but interestingly showed that the dog had preexisting arthritic changes in the carpal joints of both front legs. Thus, although this dog did have an acute agility injury, he had chronic problems, too. In fact, it is possible that the arthritis contributed to his lack of coordination in approaching the jump.
Once Shadow was on the mend, his human teammate had many questions for me. How common is carpal arthritis in performance dogs? How painful is carpal arthritis and what can be done to relieve the pain? Will Shadow still be able to play agility, obedience and other fun doggie games? Since carpal arthritis is quite common, I thought I would share the answers in this column.
In the last several years, while doing sports-medicine consultations for performance dogs across Canada and the United States, I have seen many canine athletes with carpal arthritis. Interestingly, this condition is much more common in dogs that have had their front dewclaws removed. To understand why, it is helpful to understand the structure of the carpus. This joint consists of seven bones that fit together like fieldstones that are used to build the walls of a house
The carpus joins to the radia and ulnar bones (equivalent to our lower arm), and to the metacarpal bones (equivalent to our hand). Each bone of the carpus has a convex or concave side that matches a curve on the adjacent bone. Unlike the bones of the elbow, for example.
The elbow bones have ridges that slide into interlocking grooves the bones of the carpus do not have ridges that slide into interlocking grooves on the adjacent bone. The relatively loose fit of the carpal bones is supported by ligaments that join each of the carpal bones to the adjacent bones.
With so many carpal bones that don't tightly interlock with the adjacent bones, the ligaments of this joint can be easily stretched and even torn when torque (twisting) is applied to the leg. The dewclaws have the important function of reducing the torque that is applied to the front legs, especially when dogs are turning at a canter (the main gait used in agility).
In the canter, there is a moment during each stride when the dog's accessory carpal pad (on the back of the carpus) of the lead front leg touches the ground and the rear legs and other front leg swing forward to prepare for the next stride. At this point, the dewclaw is in contact with the ground and if the dog turns, the dewclaw can dig in for extra traction to prevent unnecessary torque on the front leg. Without the gripping action of the dog's 'thumbs’ there is more stress on the ligaments of the carpus. This may cause the ligaments to stretch and tear over time, resulting in joint laxity and ultimately, arthritis.
There are many more options for treating dogs with arthritis today than there were just a few years ago. Here are some of them.
1) Weight reduction. The more weight your dog carries around, the more stress there will be on the joints. This is a particular problem in dogs with carpal arthritis, because the front legs bear 65 per cent of the dog's weight.
2) Massage. This is an excellent way to prevent excess scar tissue from forming and to keep your dog's joints flexible. Make an appointment with a canine massage therapist and learn how to do massage that is targeted to your dog's carpi. You can do the massage while you watch television in the evenings.
Afterward, gently flex and extend your dog's front legs two to three times to help promote flexibility.
3) Acupuncture. Acupuncture is often very helpful in relieving joint pain and slowing the progression of arthritis.
4) Chiropractic adjustments. Many dogs with painful joints will benefit from regular chiropractic adjustments because they are using their muscles unevenly to avoid pain on one side or the other.
5) Joint-protective nutraceuticals. There are many products on the market, and all are not created equal, so be sure to buy a product from a reputable company. For best results use a combination of glucosamine, chondroitin, methylsulfonylmethane (MSM) and cetylmyristolate (CM).
6) Antioxidant and anti-inflammatory food and supplements. Feed your dog natural antioxidant foods such as fresh vegetables and fruits that contain vitamin C. Supplement his diet with vitamins E and
B and an appropriate combination of omega-6 and omega-3 fatty acids.
7) Anti-inflammatory drugs. Talk to your veterinarian about whether' your dog should be taking antiinflammatory drugs and if so, whether he should take them only when he is in pain or on a regular basis. Because of common side effects such as gastric ulcers, I usually suggest that anti-inflammatory drugs be used only intermittently when the dog is having a painful bout. There may come a-time however, when regular doses of anti-inflammatory drugs may be necessary to give your dog the quality of life he deserves.
8) Moderate ongoing exercise. Dogs with arthritis need enough exercise to keep their muscles strong so that they support the joints, but not so much that it causes excessive wear and tear on the joints and the ligaments that support them.
Moderation is the key. Dogs should get a moderate amount of balanced exercise each day, and avoid being weekend warriors. Avoid high-impact exercise as much as possible. For example, don't use stairs as a way to exercise your dog because of the impact on descending, and don't let him run over rough, uneven ground.
Have your dog jump full height only about 10 per cent of the time during training, and only on surfaces that are smooth and appropriately cushioning, such as thick grass or properly prepared dirt (arena) surfaces. Swimming is a great exercise for arthritic dogs.
Even if your dog doesn't currently suffer from arthritis, keep this article for later. If you should be lucky enough to have your canine companion in his senior years, these tips may make it possible for him to keep running and playing like a youngster.
Those of us with responsibility for the health of canine athletes need to continually read and evaluate new scientific studies to ensure that we are taking the most appropriate care of our performance dogs. This article provides evidence through a number of recent studies to suggest that veterinarians and owners working with canine athletes should revisit the standard protocol in which all dogs that are not intended for breeding are spayed and neutered at or before 6 months of age.

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