Long-term risks and benefits of early-age gonadectomy in dogs

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.     

Long-term outcome of gonadectomy performed at an early age or traditional age in cats

OBJECTIVE: To determine long-term results and complications of gonadectomy performed at an early age (prepubertal) or at the traditional age in cats. DESIGN: Cohort study. ANIMALS: 263 cats from animal shelters. PROCEDURE: Cats that underwent gonadectomy were allotted to 2 groups on the basis of estimated age at surgery (traditional age, > or = 24 weeks old; prepubertal, < 24 weeks old). Adoptive owner information was obtained from shelter records, and telephone interviews were conducted with owners to determine physical or behavioral problems observed in the cats after adoption. Follow-up information was obtained from attending veterinarians for cats with complex problems or when owners were uncertain regarding the exact nature of their cat's problem. RESULTS: Compared with traditional-age gonadectomy, prepubertal gonadectomy did not result in an increased incidence of infectious disease, behavioral problems, or problems associated with any body system during a median follow-up period of 37 months. Additionally, the rate of retention in the original adoptive household was the same for cats that underwent prepubertal gonadectomy as those that underwent traditional-age gonadectomy. CONCLUSIONS AND CLINICAL RELEVANCE: Prepubertal gonadectomy may be performed safely in cats without concern for increased incidence of physical or behavioral problems for at least a 3-year period after gonadectomy.     

Pharmacokinetics of intravenous ketorolac in cats undergoing gonadectomy

AIM: To determine the pharmacokinetics of ketorolac tromethamine (0.5?mg/kg) when administered I/V to cats undergoing gonadectomy.

METHODS: Ketorolac was administered to nine female and three male shorthair domestic cats as an I/V bolus of 0.5?mg/kg after intubation, and 20 minutes prior to ovariectomy or orchiectomy. Intra-operative cardiorespiratory variables were monitored and blood samples were collected over 24 hours. Concentrations of ketorolac in serum were determined by high-performance liquid chromatography to establish pharmacokinetic parameters.

RESULTS: During surgery, mean end tidal isoflurane concentration was 1.63 (SD 0.24)% and normocapnia and spontaneous ventilation were maintained in all animals. The kinetics of ketorolac was described by a two-compartment model. The distribution and elimination half-lives were 0.09 (SD 0.06) and 4.14 (SD 1.18) hours, respectively. The body clearance was 56.8 (SD 33.1) mL/h/kg. The volume of distribution at steady-state and the mean residence time were 323.9 (SD 115.7) mL/kg and 6.47 (SD 2.86) hours, respectively.

CONCLUSION AND CLINICAL RELEVANCE: On the basis of the results, concentrations of ketorolac in serum in cats were above the human effective concentrations for 5–6 hours postoperatively. However, other studies including a control group are advocated to further investigate the ketorolac kinetics and the analgesic efficacy in this species.     

Spontaneous hormonal variations in male cats following gonadectomy

The increased prevalence of obesity after neutering in cats is problematic in veterinary practice. Although many factors seem to be involved, the role of prolactin (PRL) and insulin-like growth factor-I (IGF-I), both implicated in adipose tissue development and glucose intolerance, should be considered. Seven male cats were castrated when 11 months old. Body weight was then recorded for 56 weeks and PRL, IGF-I and leptin assayed for 44 weeks. Body weight increased steadily but only significantly after 36 weeks. It stabilised after 44 weeks, and the cats then gained about 20% of their initial body weight. IGF-I increased rapidly and was significantly higher by week 3. PRL and leptin increased with initial peaks during the eighth and eleventh weeks, respectively. This study confirms that castration rapidly modifies the hormonal balance, partly explaining the body weight increase, and that hormonal changes precede this body weight increase. Hyperleptinaemia is apparently a consequence of excess weight.     

Determining the optimal age for gonadectomy of dogs and cats

Elective gonadectomy of dogs and cats is one of the most common veterinary procedures in the United States. Increasingly, dog owners and members of the veterinary profession throughout the world have questioned the optimal age for performance of these procedures and whether these procedure should even be performed as elective surgeries.     

Oestradiol and genistein reduce food intake in male and female overweight cats after gonadectomy

AIM: To determine if exogenous oestradiol or the phyto-oestrogen genistein could reduce food intake in male and female cats fed ad libitum that had been allowed to accrue excessive bodyfat following neutering. METHODS: Sixteen adult (eight female, eight male) cats were neutered and allowed to increase their bodyweight (BW) through feeding ad libitum of a complete and balanced dry diet. Oestradiol was injected subcutaneously for 5-day periods in incremental doses (0.25-4 microg per cat), then food intake was recorded, and vaginal cytological changes were observed in females. Similarly, genistein was administered orally for 5-day periods in incremental doses (5-100 mg/kg). RESULTS: In males and females, both oestradiol (p<0.001) and genistein (p=0.037) significantly reduced food intake during treatment, and the minimum daily doses that produced a significant effect were 0.5 mug and 100 mg/kg, respectively. The minimum daily dose of oestradiol that produced a significant effect on food intake was not associated with changes in vaginal cytology over the 5-day treatment period. CONCLUSIONS AND CLINICAL RELEVANCE: Gonadal oestradiol appeared to be a key modulator of food intake in both male and female cats, and replacement of oestrogen to neutered cats via oestradiol or an oestrogen surrogate such as genistein has potential for reducing the prevalence of obesity in neutered cats.     

Effects of dietary fat and energy on body weight and composition after gonadectomy in cats

OBJECTIVE: To evaluate the effect of dietary fat and energy density on body weight gain, body composition, and total energy expenditure (TEE) in neutered and sexually intact cats. ANIMALS: 12 male and 12 female cats PROCEDURE: Male cats were castrated (castrated male [CM]) or underwent no surgical procedure (sexually intact male [IM]). Female cats underwent ovariectomy (spayed female [SF]) or laparotomy and ligation of both uterine tubes without ovary removal (sexually intact female [IF]). Cats were fed either the low-fat (LF) or high-fat (HF) diet for 26 weeks, with the final allocation consisting of 8 groups: IF-LF IF-HE SF-LF, SF-HF IM-LF, IM-HF, CM-LF, and CM-HF. Mean food intake for each group was recorded daily, and body weight was monitored weekly throughout the study. Body composition and TEE were measured before surgery in week 0 and at the end of the study (week 26) by isotope dilution (double-labelled water). RESULTS: N eutered cats gained significantly more body fat and body weight (53.80+/-5.79%) than sexually intact cats (27.11+/-5.79%) during the study. Body weight gain of neutered cats fed the HF diet was greater than those fed the LF diet. Following correction for body composition, TEE was similar in all groups and no pattern towards increased food intake was evident. CONCLUSIONS AND CLINICAL RELEVANCE: Weight gain in neutered cats was decreased by feeding an LF, low energy-dense diet. To prevent weight gain in cats after neutering, a suitable LF diet should be fed in carefully controlled meals rather than ad libitum.     

Elevation of plasma cholecystokinin concentration following a meal is increased by gonadectomy in male cats

An overweight or obese body condition commonly develops after gonadectomy (GX) in domestic cats. The cause appears to be a rapid, quantal (approximately 12%), increase in food intake that is sustained and probably mediated by withdrawal of gonadal hormone. Recently, an interaction of gonadal hormone and cholecystokinin (CCK) effectiveness has been suggested. A reduction in the satiating potency of intestinal CCK was presently hypothesized to contribute to the disturbance of food intake control caused by GX in domestic cats. Pre- and post-prandial intestinal CCK secretion as indicated by plasma CCK concentrations were determined in 16 adult male cats (5.1 +/- 0.1 kg) 8 weeks before and 57 weeks after eight of the cats were gonadectomized. During ad libitum intake of a commercial dry, expanded diet, body weight increased from 22% to 28% in gonadectomized cats and was unchanged in intact cats. Baseline CCK concentrations were not different between gonadectomized and intact cats. Amounts of diet ingested during CCK determinations were 15-19% of daily metabolizable energy requirement and were not different between gonadectomized and intact cats. The post-prandial area under the curve (AUC; 0-400 min) CCK concentration increased linearly with meal size (p < 0.01) and was not correlated with body weight. Area under the curve CCK concentration, when normalized for meal size, was 34% greater (p < 0.01) in gonadectomized cats than that in intact cats. The findings indicate GX increases meal-induced intestinal CCK secretion and therefore, do not support the study hypothesis. The findings indicate GX may slow digestion and absorption and attenuate inhibition of food intake by CCK.     

Comparative vaccine-specific and other injectable-specific risks of injection-site sarcomas in cats

Objective-To compare associations between vaccine types and other injectable drugs with development of injection-site sarcomas in cats. Design-Case-control study. Animals-181 cats with soft tissue sarcomas (cases), 96 cats with tumors at non-vaccine regions (control group I), and 159 cats with basal cell tumors (control group II). Procedures-Subjects were prospectively obtained from a large pathology database. Demographic, sarcoma location, basal cell tumor, and vaccine and other injectable history data were documented by use of a questionnaire and used to define case, control, and exposure status. Three control groups were included: cats with sarcomas at non-vaccine sites, cats with basal cell tumors, and a combined group of cats with sarcomas at non-vaccine sites and cats with basal cell tumors. χ(2) tests, marginal homogeneity tests, and exact logistic regression were performed. Results-In the broad interscapular region, the frequency of administration of long-acting corticosteroid injections (dexamethasone, methylprednisolone, and triamcinolone) was significantly higher in cases than in controls. In the broad rear limb region, case cats were significantly less likely to have received recombinant vaccines than inactivated vaccines; ORs from logistic regression analyses equaled 0.1, with 95% confidence intervals ranging from 0 to 0.4 and 0 to 0.7, depending on control group and time period of exposure used. Conclusions and Clinical Relevance-This case-control study measuring temporal and spatial exposures efficiently detected associations between administrations of various types of vaccines (recombinant vs inactivated rabies) and other injectable products (ie, long-acting corticosteroids) with sarcoma development without the need to directly measure incidence. These findings nevertheless also indicated that no vaccines were risk free. The study is informative in allowing practitioners to weigh the relative merits and risks of commonly used pharmaceutical products.     

Long-term outcome of gonadectomy performed at an early age or traditional age in dogs

OBJECTIVE: To determine long-term results and complications of gonadectomy performed at an early age (prepubertal) or at the traditional age in dogs. DESIGN: Cohort study. ANIMALS: 269 dogs from animal shelters. PROCEDURE: Dogs that underwent gonadectomy were allotted to 2 groups on the basis of estimated age at surgery (traditional age, > or =24 weeks old; prepubertal, < 24 weeks old). Adoptive owner information was obtained from shelter records, and telephone interviews were conducted with owners to determine physical or behavioral problems observed in the dogs since adoption. Follow-up information was obtained from attending veterinarians for dogs with complex problems or when owners were uncertain regarding the exact nature of their dog's problem. RESULTS: Prepubertal gonadectomy did not result in an increased incidence of behavioral problems or problems associated with any body system, compared with traditional-age gonadectomy, during a median follow-up period of 48 months after gonadectomy. Rate of retention in the original adoptive household was the same for dogs that underwent prepubertal gonadectomy as those that underwent traditional-age gonadectomy. Infectious diseases, however, were more common in dogs that underwent prepubertal gonadectomy. CONCLUSIONS AND CLINICAL IMPLICATIONS: With the exception of infectious diseases, prepubertal gonadectomy may be safely performed in dogs without concern for increased incidence of physical or behavioral problems during at least a 4-year period after gonadectomy.     

Possible therapeutic benefits of adenosine-potentiating drugs in reducing age-related degenerative disease in dogs and cats

Adenosine is a ubiquitous, biologically important molecule that is a precursor of other biologically active molecules. It also is a component of some co-factors and has distinct physiological actions in its own right. Levels are maintained by synthesis from dietary precursors and re-cycling. The daily turnover of adenosine is very high. Adenosine can act either as a hormone by binding to adenosine receptors, four adenosine receptor subtypes have been identified, and as an intracellular modulator, after transport into the cell by membrane transporter proteins. One of the principal intracellular actions of adenosine is inhibition of the enzyme phosphodiesterase. Extracellular adenosine also has specific neuromodulatory actions on dopamine and glutamate. Selective and nonselective agonists and antagonists of adenosine are available. The tasks of developing, evaluating and exploiting the therapeutic potential of these compounds is still in its infancy. Adenosine has actions in the central nervous system (CNS), heart and vascular system, skeletal muscle and the immune system and the presence of receptors suggests potential actions in the gonads and other organs. Adenosine agonists improve tissue perfusion through actions on vascular smooth muscle and erythrocyte fluidity and they can be used to improve the quality of life in aged dogs. This article reviews the therapeutic potential of adenosine-potentiating drugs in the treatment of age-related conditions in companion animals, some of which may be exacerbated by castration or spaying at an early age.     

Long-term survival following embolectomy in two cats with aortic embolism

Two cats suffering from aortic embolism were subjected to embolectomy, preceded in one case by the administration of the 5-hydroxytryptamine antagonist, cyproheptadine, and followed in both by the administration of heparin and acetylsalicylic acid. Both animals made a good functional recovery and are in good health 2 years after surgery. The rationale underlying the medical therapy is discussed.     

Veterinary attitudes towards pre-pubertal gonadectomy of cats: a comparison of samples from New Zealand,Australia and the United Kingdom

AIM: To compare the attitudes and practices of a sample of veterinarians in New Zealand, Australia and the United Kingdom (UK) towards pre-pubertal gonadectomy of cats.

METHODS: Respondents' demographics were gathered using an electronic questionnaire distributed via professional veterinary associations in the target countries, as were minimum age at gonadectomy and typical age of puberty. Desirability of prepubertal gonadectomy was gauged using three response categories (‘yes’, ‘no’ or ‘sometimes’), respondents were then able to justify the response given. Two-way Analyses of Variance (ANOVA) followed by post hoc Tukey HSD tests were used to test whether there were differences in minimum ages for gonadectomy within and between countries and between providers and non-providers of services to pounds (or animal welfare centres). Views on the desirability of prepubertal gonadectomy relative to demographics were explored using a Likelihood Ratio Test.

RESULTS: The survey received 717 responses. Most respondents believed pre-pubertal gonadectomy was either entirely or ‘sometimes’ desirable (556/621), few thought it was undesirable (65/621). Minimum age at gonadectomy was significantly affected by country surveyed and provision or non-provision of services for pounds. Post hoc Tukey HSD analysis indicated the mean age of both spaying and castration (4.3 months) in the UK was significantly different from both Australia (spaying: 3.4 months, castration: 3.2 months) and New Zealand (spaying: 3.4 months, castration: 3.2 months) (all p<0.001). Mean ages at spaying and castration were also significantly different (p= 0.008; p= 0.019, respectively) for non-providers (spaying: 3.9 months, castration: 3.8 months) of services to pounds when compared to providers (spaying and castration: both 3.6 months).

Likelihood Ratio Tests indicated significant effects amongst countries and between genders relative to the desirability of pre- pubertal gonadectomy. Respondents from the UK were more likely to answer ‘no’ (p = 0.004) or ‘sometimes’ (p = 0.050) as compared to those from New Zealand or Australia. Females were more likely to respond with ‘sometimes’ as opposed to ‘yes’ than males. Reasons for considering pre-pubertal gonadectomy desirable or sometimes desirable focussed on reducing unwanted pregnancies and improving population control, as well as improving rates of adoption, owner compliance and cat behaviour and health.

CONCLUSIONS AND CLINICAL RELEVANCE: In general, pre-pubertal gonadectomy is considered a desirable procedure by those practitioners that responded to the survey. However age at which any such procedure occurs differs depending upon a number of factors. Differences among countries may relate to the specific veterinary association's guidelines or possibly differences in social discourse which affect perception of cats. There is substantial overlap between the reported minimum age of gonadectomy and the age at which cats can enter early puberty, allowing a window for unintentional pregnancy when pre-pubertal gonadectomy does not occur.