Contraception in the dog and cat

Investigating the influence of neuter status on paw preference in dogs and cats

Motor lateralization is commonly observed through preferential paw use in dogs and cats. Previous studies have uncovered sex-related differences in paw preference, hypothesizing that these differences may be related to sex hormones. The current study aimed to compare neutered and entire individuals to further investigate whether paw preference is influenced by sex hormones. Dog and cat owners were required to fill in a questionnaire with demographic information such as sex and neuter status of their pets. They then carried out two simple paw preference tasks within their homes: a "reaching for food" task and a "reaching for a toy" task. This study revealed an overall preference among the 272 dogs and 137 cats tested to use their right paw in both tasks. In cats, the degree of paw preference (i.e., regardless of the direction) was significantly influenced by an interaction between neuter status and life stage. Also in dogs, both life stage and an interaction between neuter status and life stage tended to influence the degree of paw preference. Post-hoc power analysis revealed a lack of statistical power, suggesting that future studies using a larger sample size are needed to further investigate potential effects of neuter status on paw preference.

Progestins to control feline reproduction

Relevance:

The high fertility rate of cats means that methods to control feline reproduction are a requirement for cat breeders and pet owners, as well as for those involved in the management of feral cat populations. Progestins continue to be used to prevent queens from cycling, and also as an adjunct or alternative to surgical sterilization within trap–neuter–return (TNR) programs.

Evidence base:

A considerable body of information exists on megestrol acetate (MA) and medroxyprogesterone acetate (MPA), thanks to the many studies and case reports published in the scientific literature over the past 50 years documenting their clinical use in cats. Comparatively less is known about the use in cats of more recent progestins such as levonorgestrel, proligestone, delmadinone, chlormadinone and altrenogest.

Dosing, safety and efficacy:

Based on a combination of dose, frequency and duration of treatment, MA can be categorized into low (0.625 mg/kg/week for up to 30 weeks), medium (0.625 mg/kg q24h for 1 week or q48h for up to 2 weeks) and high (0.625 mg/kg q24h or q48h for several weeks, or weekly for months or years) dosages. Studies suggest that low dosages can be used relatively safely in cats, while higher dosages increase the risk and severity of adverse reactions. Early work showing that an oral MPA dosage of 0.01 mg/kg administered q24h for 12 months suppresses oestrus in queens effectively and safely has not been considered, and much higher MPA dosages (>6.25 mg/kg q24h) have been used in cats over the past 40 years.

Recommendations:

Progestins should always be used with caution. Using the lowest possible dosages, MA and MPA may, however, continue to be used safely in pet queens as well as (in conjunction with TNR programs) for the control of feral cat colonies. More recent progestins appear to be effective and safe, albeit their efficacy and safety need to be further investigated.

Effects of ovariohysterectomy on reactivity in German Shepherd dogs

This study investigated the effects of ovariohysterectomy on reactivity of German Shepherd dogs. Fourteen healthy dogs ranging in age from 5 to 10 months were assigned to an ovariohysterectomy or a sexually intact group. Their behaviours were digitally video recorded 4-5 months after treatment and analysed for treatment effects on reactivity. Responses to the approach of an unfamiliar human leading an unknown dog were assigned the following reactivity scores: severe reactivity, 3; moderate reactivity, 2; defensive or mild reactivity, 1; attentive or no reactivity, 0. Median reactivity scores in response to the approach of an unfamiliar human walking with an unknown dog were calculated for each observation period. Dogs in the ovariohysterectomized group showed more reactivity, and median reactivity scores were higher in the ovariohysterectomy group compared with those of the sexually intact group. Ovariohysterectomy of 5-10 month old German Shepherd bitches specifically, and perhaps bitches of any breed generally, may induce an increase in reactivity. Practitioners may benefit from recognizing that a range of behavioural changes may occur post-ovariohysterectomy.

Non-surgical methods of contraception and sterilization

The Humane Society of the United States estimates that each year between 8 and 10 million dogs and cats enter shelters and 4-5 million of these animals are euthanized due to lack of homes. Many veterinarians within the United States recommend surgical sterilization for population control in dogs and cats. However, there are non-surgical methods to control reproduction. Pharmacologic methods of contraception and sterilization can be safe, reliable and reversible. Hormonal treatments using progestins, androgens, or gonadotropin releasing hormone (GnRH) analogs act to either directly block reproductive hormone receptor-mediated events, or indirectly block conception via negative feedback mechanisms. Immunocontraception, via vaccination against GnRH, the luteinizing hormone receptor or zona pellucida proteins, is also possible. Intratesticular or intraepididymal injections provide a method for non-surgical sterilization of the male dog and cat. Additional methods have been employed for mechanical disruption of fertility including intravaginal and intrauterine devices and ultrasound testicular ablation. Alternative approaches to surgical sterilization will be reviewed.

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.

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.

Diethylstilboestrol--clinical pharmacology and alternatives in small animal practice

Diethylstilboestrol is currently only available in Australia for oral use in dogs and cats. As an orally and systemically active non-steroidal oestrogen, DES has been widely used in small animal veterinary medicine for a variety of indications. A review of the literature reveals that many of the recommendations for use are founded on anecdotal or unreported clinical observations. While many of the uses may be valid, accurate determinations of optimum dosing regimens have not been defined. This is especially unfortunate in view of the potential toxicity of DES to small animals. Nevertheless, particularly in cases of low-dose intermittent administration, oral DES appears indicated at least until data on alternative safe and effective interventions become available.