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dogs and cats. No decrease in urethral diameter (and therefore no increased risk of lower urinary tract disease) has been observed in neutered male cats (regardless of age at neutering) compared to the intact population, with no difference in urethral closure pressure in neutered vs intact female cats, while there was a significant decrease in the diameter of the pre-pelvic urethras in queens neutered at 7 weeks13. Glucose metabolism (glucose half life, peak serum insulin concentrations, peak insulin response following intravenous glucose administration) was not altered in neutered (regardless of age at neutering) compared to intact cats when evaluated at 6, 12, 18 months of age, while at 24 months of age neutered male cats had a significantly later peak serum insulin response when compared to intact cats 13.
Behavioral changes
Effects of prepuberal gonadectomy on behaviour
vary depending on species and sex and have
not been completely investigated yet. In general, excitability and degree of activity are increased in males and females gonadectomised at 7 weeks or 7 months15,16,17. However, inappropriate behaviors as reasons for relinquishment have not been reported in dogs neutered at an early age wen compared to those neutered as adults, and in Labrador/Golden Retriever crosses raised as guide dogs for the blind, neutering at 7 weeks or 7 months does not affect the degree of training success. No effect of early age neutering on playfulness, excitement or frequency of vocalization has been reported in cats. In cats castrated prior to
5 months of age there is a decrease in activity and
an increase of shyness towards strangers 15,16. In
adult bitches castration may exhacerbate dominance regardless of their attitude prior to surgery. A significant increase in the degree of reactivity has been observed in German sheperd bitches 5 months following OVX18. Owners should realize the importance of evaluating the behaviour of their bitches prior to deciding whether to castrate them as castration may not be the appropriate treatment for behavioural problems17.
Obesity - Obesity is reported as a common side effect of neutering7. No difference in food intake, weight gain or back-fat depth was reported for the first 15 months following neutering when a total of 32 neutered and intact dogs were compared. However, food intake increases significantly in bitches during the first 90
days following OVX/OVH with respect to bitches receiving a sham-laparotomy. Larger studies indicate that, irrespective of age at surgery, spayed female dogs are about twice as likely to become obese as intact animals. The risk for obesity does not change in animals gonadectomized prepuberally. It is unknown whether there is a predisposition to obesity, but if this is the
case gonadectomy seems to have the same stimulus regardless of age. Obesity is also a side effect of
neutering in cats, as intact animals have a lower weight and a lower fat thickness than cats neutered at 7 weeks or 7 months. The resting metabolic rate is lower and body condition scores are higher in gonadectomised (irrespective of age at neutering) compared to intact cats. Appetite increases significantly in gonadectomized cats 3 days after surgery. In castrated tomcats, a significant increase in body weight 35 weeks post-castration
was preceded by significant increases in serum concentrations of Insulin Growth Factor I, prolactin and leptin in castrate toms 1, 7 and 11 weeks following surgery, respectively19.
Urinary Incontinence - A decreased capacity of the external urethral sphincter is observed following gonadectomy in bitches but not in queens. Average urethral closure pressure in intact bitches is 18.6+10.5
cm H20, 12 months following gonadectomy is 10.3+6.7 cm H20 in continent bitches, and may fall to 4.6+2.3 cm H20 in incontinent animals. Urinary incontinence (UI) is
a common sequel of spaying in bitches, with the interval between spaying and diagnosis of incontinence varying from days to months or even years. Incidence of UI in the normal canine population varies from 0.3 to 2.0%, while
it increases to 5-10% in the spayed bitches population.
In a long-term study on risks and benefits of early age neutering in dogs, the incidence of UI was reported to increase in bitches neutered prior to 3 months of age when compared to that of bitches neutered after 3 months, therefore the age of 3 months was indicated as a threshold afer which female puppies could be safely neutered15. However, many authors think that going through puberty may have a beneficial effect as it allows the reproductive system to reach its final stage of growth thereby perhaps limiting the incidence of side effects such as UI as well as those due to insufficient growth of external genitalia.
Osteoporosis – Osteoporosis (loss of trabecular bone) is the most important complication of menopause in women and is thought to be due to a lack of estrogen stimulation causing reduced secretion of calcitonin.
Loss of trabecular bone has been observed in Beagle bitches 11 months following OVH 20, although at present it is unclear whether this bears any clinical significance presumably because of the short life-span of most of the dogs used as companion animals.
Surgical complications - Generic surgical risk may be significant in females due to the laparotomy access
and of little if any significance in males. Side effects
of gonadectomy in bitches and queens have been reported11, 21-25 and include haemorrage/granuloma of the ovarian or (more commonly) uterine pedicle, suture dehiscence/infection/abscess/edema, peritonitis, evisceration, formation of suture fistulas, retention
of a cotton gauze, ureteral ligation with secondary hydronephrosis, formation of vesicovaginal fistula with
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