Veterinary Abstracts
Health Considerations
PRESENTATION SUMMARY & POWERPOINT
Risks and Benefits of Neutering
and Early-Age Neutering in
Dogs and Cats: Effects on Development,
Obesity, and Select
Orthopedic and Neoplastic Conditions
C. Victor Spain, Philadelphia, Pennsylvania
Neutering of dogs and cats confers a mix of
benefits and adverse risks. The objective of
this presentation is to highlight recent research
findings on the associations between neutering
(whether early-age or at a traditional age)
and select medical conditions. In this abstract,
the term neutering is used in the broadest
sense to include both castration of male dogs
and cats or ovariohysterectomy (or ovariectomy)
of female dogs and cats. The
data on early-age neutering is from a retrospective
cohort study of 1,579 cats and 1,659 dogs adopted
from a large animal shelter between 1989 and
1998 (Spain, 2004). Obesity.
Several studies have indicated an increased
prevalence of obesity in neutered dogs and
cats. Energy
consumption appears to decrease after neutering
in dogs and cats, although the degree and timing
varied between studies. Some researchers attribute
neutering-related obesity in cats to increased
food consumption and not to altered metabolic
rate, suggesting that the weight gain can be
prevented with a lower fat diet (German, 2006,
Nguyen, 2004, Kanchuck, 2002). Obesity does
not appear to be affected
by age of neutering in cats, but among
dogs, early-age neutering is associated with
a lower incidence of obesity than neutering
after 6 months of age (Spain, 2004). Canine
Hip Dysplasia (CHD) and Cranial Cruciate Ligament
(CCL) Injury. One study found an increased
incidence of CHD after neutering in boxers
(van Hagen, 2005), and among dogs seen in an
orthopedic surgical clinic, the prevalence
of CCL injury among neutered dogs (4.7%) was
more than twice that of intact dogs (2.3%)
(Slauterbeck, 2004). These findings regarding
CCL injury incidence are consistent with findings
that the level of sex hormones affects the
incidence of anterior cruciate ligament (ACL)
rupture in humans. Hip dysplasia is increased
among early-neutered dogs compared to those
neutered after 6 months of age (Spain, 2004). Mammary
Cancer and Prostatic Cancer. Spaying
before 1 year of age reduces the risk of mammary
carcinoma approximately 90% in cats, and spaying
before second estrus in dogs similarly reduces
the risk by about 90% (Overley, 2005). The
incidence of mammary cancers does not vary
between ovariohysterectomy (traditional spay
with removal of the uterus and ovaries) and
ovarioectomy (removal of just the ovaries)
(van Goethem, 2006). Traditional
thought is that neutering reduces the risk
of prostatic cancer
among male dogs. Recent research suggests that
after neutering, however, changes in endothelin,
a cell protein involved in cell growth, may
eventually reverse the benefits of neutering
on prostatic cancer risk (Padley, 2002) and
the incidence of prostatic cancer may actually
be higher in castrated dogs than intact dogs
(Teske, 2002).
Select References
Early-age neutering
CV Spain, JM Scarlett, KA Houpt, 2004.
Long-term risks and benefits of pediatric
gonadectomy in cats. Journal of the American
Veterinary Medical Association. 224(3):372-379.
CV Spain, JM Scarlett, KA Houpt, 2004.
Long-term risks and benefits of pediatric
gonadectomy in dogs. Journal of the American
Veterinary Medical Association . 224(3):380-387.
CV Spain, JM Scarlett, SM Cully, 2002.
When to neuter dogs and cats: a survey
of New York state veterinarians’ practices
and beliefs. Journal of the American
Animal Hospital Association, 38(4): 482-488.
Physical development and obesity
M Hoenig, DC Ferguson, 2002. Effects of neutering
on hormonal concentrations and energy requirements
in male and female cats. American Journal of
Veterinary Research. 63(5): 634-639. AJ German.
2006. The growing problem of obesity in dogs
and cats. Journal of Nutrition.136: 1940S-1946S.
PG Nguyen, HJ Dumon, BS Siliart, et al. 2004.
Effects of dietary fat and energy on body weight
and composition after gonadectomy in cats.
American Journal of Veterinary Research. 65(12):1708-1713.
ML Kanchuck, RC Backus, CC Calvert, et al.,
2002. Neutering induces changes in food intake,
body weight, plasma insulin and leptin concentrations
in normal and lipoprotein lipase-deficient
male cats. Journal of Nutrition. 132:1730S-1732S.
PD McGreevy, PC Thompson, C Pride, et al.,
2005. Prevalence of obesity in dogs examined
by Australian veterinary practices and the
risk factors involved. The Veterinary Record.
156:695-702.
Orthopedic disorders
JR Slaughterbeck, K Pankratz, KT Xu, et al.
2004. Canine ovariohysterectomy and orchiectomy
increases the prevalence of ACL injury. Clinical
Orthopedics and Related Research. 429: 301-305.
MAE van Hagen, BJ Ducro, J van den Broek, et
al., 2005. Incidence, risk factors, and heritability
estimates of hind limb lameness caused by hip
dysplasia in a birth cohort of Boxers. American
Journal of Veterinary Research. 66(2):307-312.
Mammary and prostate cancer
RJ Padley, DB Dixon, JR Wu-Wong, 2002. Effects
of castration on endothelin receptors. Clinical
Science. 103(suppl. 48):442S-445S. B Overley,
FS Shofer, MH Goldschmidt, et al., 2005. Association
between
ovariohysterectomy and feline mammary cancer.
Journal of Veterinary Internal
Medicine. 19:560-563. B van Goethem, A Schaefers-Okkens,
J Kirpensteijn, 2006. Making a rational choice
between ovariectomy and overiohysterectomy
in the dog: A discussion of the benefits of
either technique. Veterinary Surgery. 35:136-143.
E Teske, EC Naan, EM van Dijk, et al., 2002.
Canine prostate carcinoma: epidemiologic evidence
of an increased risk in castrated dogs. Molecular
and Cellular Endocrinology.197:251-255
Journal of the American Veterinary
Medical Association 224(3):
380-387. ISSN:
0003-1488. Spain, C., J. Scarlett, and K. Houpt
(2004).
Long-term risks and benefits of early-age
gonadectomy in dogs.
NAL Call Number: 41.8
Am3
OBJECTIVE: To evaluate the long-term risks and benefits
of
early-age gonadectomy, compared with traditional-age
gonadectomy,
among dogs adopted from a large animal shelter. DESIGN:
Retrospective
cohort study. ANIMALS: 1,842 dogs.
PROCEDURE: Dogs
underwent
gonadectomy and were adopted from an animal
shelter before 1 year of
age; follow-up was available for as long as
11 years after surgery.
Adopters completed a questionnaire about their
dogs' behavior and
medical history. When possible, the dogs' veterinary
records were
reviewed. Associations between the occurrence
of 56 medical and
behavioral conditions and dogs' age at gonadectomy
were evaluated.
RESULTS: Among
female dogs, early-age gonadectomy was associated
with increased rate of cystitis and decreasing
age at gonadectomy was associated with increased
rate of urinary incontinence. Among male and
female dogs with early-age gonadectomy, hip
dysplasia, noise phobias, and sexual behaviors
were increased, whereas
obesity, separation anxiety, escaping behaviors,
inappropriate elimination when frightened,
and relinquishment for any reason were decreased.
CONCLUSIONS AND CLINICAL
RELEVANCE: Because early-age gonadectomy
appears to offer more benefits than risks for
male dogs, animal shelters can safely gonadectomize
male dogs at a young age and veterinary practitioners
should consider recommending routine gonadectomy
for client-owned male dogs before the traditional
age of 6 to 8 months. For female dogs, however,
increased urinary incontinence suggests that
delaying gonadectomy until at least 3 months
of age may be beneficial.
J
Anim Physiol Anim Nutr (Berl). 2001 Aug;85(7-8):195-9.
Leptin, body fat content and energy
expenditure in intact and gonadectomized adult
cats: a preliminary study.
Martin
L, Siliart
B, Dumon
H, Backus
R, Biourge
V, Nguyen
P. Laboratory of Nutrition
and Endocrinology, National Veterinary School
of Nantes, Nantes France.
The present study was conducted to assess the body composition, leptin, and energy expenditure changes following gonadectomy in cats. Twenty-one females (12 intact and nine spayed) and 21 males (11 intact and 10 castrated) were used. Body weight was recorded. Serum plasma leptin was measured by radioimmunoassay and body composition and energy expenditure were assessed after injection of doubly labelled water. These results confirmed the gain in body weight and body fat following neutering and demonstrated a strong linear relationship between body fat and serum level of leptin. Energy expenditure decreased in castrated cats in comparison with intact ones. This study underlined the effect of gonadectomy as a major factor of obesity in cats and showed that the increase in circulating leptin reflected the amount of body fat. The present results provide further evidence that the regimen of gonadectomized cats should be carefully controlled to avoid excessive weight gain.
PMID: 11686788 [PubMed - indexed for MEDLINE]
Am
J Vet Res. 1996 Mar;57(3):371-4.
Effect of prepuberal and postpuberal
gonadectomy on heat production measured
by indirect calorimetry in male and female
domestic cats.
Root
MV, Johnston
SD, Olson
PN. Department of Small Animal
Clinical Sciences, College of Veterinary
Medicine, University of Minnesota, St Paul
55108, USA.
OBJECTIVE: To use indirect calorimetry to compare heat production between gonadectomized and sexually intact male and female cats. DESIGN--Male (n = 6) and female (n = 6) kittens were gonadectomized at 7 weeks or 7 months of age, or left sexually intact. Body heat production was measured by indirect calorimetry in all cats at 12, 18, and 24 months of age.
ANIMALS: 18 male and 18 female clinically normal domestic shorthair cats.
PROCEDURE: Heat production was measured, using an open-circuit, respiratory, indirect calorimeter. All cats underwent calorimetry at 12, 18, and 24 months of age. The heat coefficient, a measure of resting metabolic rate, was calculated for each cat at each test; heat coefficient is defined as logarithm of heat (kcal/h) divided by logarithm of body weight (kg).
RESULTS: Heat production did not vary with age in male or female cats. Heat coefficient was higher in sexually intact male and female cats than in gonadectomized male and female cats at 12, 18, and 24 months of age (12 months, females, P < 0.01, males, P = 0.04; 18 months, females, P < 0.01, males, P = 0.02; and 24 months, females and males, P < 0.01). CONCLUSIONS: These data suggest that resting metabolic rate in cats decreases after gonadectomy.
CLINICAL RELEVANCE: A decrease in metabolic rate is synonymous with a decrease in caloric requirements. Gonadectomized animals fed in a manner similar to sexually intact animals may be predisposed to obesity and its sequelae.
PMID: 8669771 [PubMed - indexed for MEDLINE]