Responsible ownership and care of domestic cats in Scotland: report

5. Measures that can protect domestic cat welfare

What are the welfare benefits/harms of compulsory microchipping of domestic cats?

The main benefits of microchipping are to ensure that lost, straying, injured or stolen animals can be reunited with their owners. As described above, the welfare of stray animals can be very poor, they may experience fear and distress from not being able to return home, and they are at high risk of injury, RTAs, poor nutrition, and entrapment. Animals without a microchip are significantly harder to return to their owners and may spend prolonged times in rescue shelters. Time spent in shelters is routinely associated with physiological or behavioural indicators of stress in research studies^{[88 ]}and hence poorer welfare, which indicates improved welfare in microchipped cats that are more quickly reunited with their owners. Scanning of cats that have been found dead can also help to provide certainty for owners of the fate of their pet. Rapid identification of the owner can also ensure timely veterinary treatment for injured cats. Compulsory microchipping may serve to reduce the rates of deliberate cat abandonment, if owners can be traced.

In order to achieve these welfare benefits, it is essential that there are well-run databases, which owners can use to provide up-to-date information, ideally a central database or a single point of search between databases to allow owners and cats to be reunited. It is essential that these are kept up to date if the benefits of microchipping in reuniting owners and pets are to be achieved. As such, to be fully effective, measures are necessary to ensure owners get their cat chipped and keep the database details up to date, e.g. use of fixed penalty notices. A secondary benefit of such as resource could also be to allow research and data collection to improve cat welfare. Similar projects have been proposed for equine welfare in the UK (e.g., Horse Life Project making use of information in the Central Equine Database, in which all equids must be registered) and for companion animals in New Zealand.

A small number of case studies have reported formation of fibrosarcoma at the site of the microchip in cats^[89], or the need to recover a microchip from the spinal cord of a cat^[90]. These incidents appear to be very rare, and are often associated with secondary issues, such as incorrect placement of the microchip. A higher frequency of welfare issues has been reported with the use of collars in cats as a means of identification, principally entrapment in the collar or strangulation. Although not the greatest risk faced by free-roaming cats, 79% of veterinarians interviewed in one study had seen at least one collar-related injury and an estimate of 0.34% of cases involved collar injuries^[92]. These data suggest that the welfare costs to the cat of being implanted with a microchip are very small, are less than those of wearing a collar as the main means of identification, and microchips have significant welfare benefits in ensuring keepership can be demonstrated and cats can be reunited with owners/keepers.

An additional benefit in making microchipping mandatory comes from the management of feral and stray cats in TNVR programmes. If teams working to neuter stray and feral cats can identify owned animals in the population the neuter and vaccination status of these animals may be known and they can be returned to their owners. Animals without microchips can be assumed to be feral and treated accordingly (neutered, vaccinated, rehomed or returned to the site of capture). This would also greatly assist conservation efforts for the wildcat in order save resources in associated TNVR schemes.

What are the welfare benefits/harms of vaccination/prophylactic treatment of domestic cats?

Vaccination is the mainstay of companion animal population health and, through preventing common or endemic diseases of cats, reduces morbidity and mortality and the poor welfare that can come from experiencing disease. As described above, use of a set of ‘core’ vaccines protects cats from the most common infectious diseases they are likely to encounter, tailored to the individual risk of each cat. Vaccination ensures that when the cat meets a field infection, it can produce a stronger and more rapid immune response than cats which are unvaccinated. Any symptoms of the disease may be eliminated or limited, and the animal generally recovers more quickly. As infectious disease can have a very negative impact on cat welfare, the benefits of vaccination are significant.

Vaccination does not prevent infection, only the impacts on the clinical expression of the disease, and vaccinated animals may still carry and excrete the pathogen, which can impact on the risks to other animals in the population or other species. However, if sufficient animals are vaccinated, this risk is small, and the level of excretion by a vaccinated cat is generally reduced compared to an unvaccinated cat. Vaccine reactions may occur, and a low-grade malaise is commonly seen for up to 24 hours after vaccination. It is estimated that around 3% of vaccinations result in a more significant vaccine response, although the welfare impacts on the cat are likely to be short-lived in the majority of cases. Vaccination in cats has been linked to the development of vaccine-associated sarcomas at the site of vaccination in 0.01% of vaccinations^[92]. However, these are small risks compared to the protection against disease afforded by vaccination.

Parasitic disease can cause significant morbidity and mortality in companion animals, and can be associated with abdominal discomfort, malaise, diarrhoea, and weight loss, as well as skin irritation, scratching, and secondary infections through broken skin and hair loss. Therefore, failure to adequately control parasitic infections can be a very significant cause of welfare harm. Concerns about increasing resistance to parasiticides of common parasites are relevant, although there is evidence that most cat owners do not comply fully with scheduled treatments, which can be a risk factor for increasing resistance^[93].

What are the welfare risks and benefits of neutering of domestic cats?

It is not possible to precisely predict the outcome of neutering for any individual. However, existing research does allow some generalisation about the magnitude and clinical importance of specific risks and benefits. The data quoted below relate to surgical neutering, unless otherwise stated. There are also ethical issues around the management of reproductive lives of companion animals, which will be discussed below.

Surgery: The process of conducting neutering surgery may have some short-term welfare impacts associated with the stress of being contained in an unfamiliar environment, procedures where pain management may not be optimal (pain assessment in cats is typically considered to be more challenging, and many veterinarians rate pain in cats as less than for dogs for an equivalent procedure), and anaesthetic or surgical complications. It has been suggested that up to 9% of neutering cases may involve one or more abnormalities^[18].

Longevity: Neutered cats live longer than unneutered cats^[94]. This increased life expectancy may be due to the preventive health benefits, and/or reduced risk-associated behaviour (such as straying and fights). Increased life expectancy may also reflect the enhanced care of neutered animals by their owners^[95,96].

Tumour incidence: The magnitude of sparing effects on the development of tumours depends on the timing of neutering. Female cats neutered prior to six months of age had a 91% reduction in the risk of malignant tumour development as compared to intact cats. Those spayed prior to one year of age had an 86% reduction in risk, while those spayed between 12 and 24 months of age had an 11% risk reduction, but after 24 months of age there was no benefit^[97]. Similar health benefits in males are not found, androgen-dependent disease being significantly less prevalent.

Obesity and neutering: Several studies indicate that neutering is a risk factor for obesity in cats, with neutered cats being 3.4 times more likely to become obese than sexually intact cats^[20,98-100]. Obesity is not a direct consequence of neutering, but it is important to control body weight in neutered animals, because of its association with increased risk of other medical problems^[101] and reduced life expectancy^[96].

Metabolic rate has been shown to decrease in cats after neutering^[98] and neutered cats were found to have a higher body mass and body condition score, and increased falciform fat in comparison with intact cats^[98,102]. Predisposition to obesity is multifactorial and other uncontrolled variables, such as diet, exercise and genetics, make it difficult to determine solely the effects of neutering on obesity^[20]. Long-term studies found no correlation between age at neutering and obesity^[103] .

Diabetes mellitus (DM): Neutered cats are not only at a higher risk of becoming obese, but also have a two- to ninefold increased risk of developing DM than sexually intact cats^[103-106]. The increased probability that cats will develop obesity and DM after neutering may be due to decreased insulin sensitivity^[99,107]. No correlation between timing of neutering and risk of developing DM has been identified, and other risk factors include breed, sex and increasing age^[20].

Behaviour: Short- and long-term studies have found some behavioural problems following neutering in cats^[102,103].

Hart and Barrett (1973)^[108] note that both spraying urine, and straying are significantly reduced in neutered males.

Among male cats that underwent early-age neutering (< 5.5 months of age), the occurrence of aggression toward veterinarians, sexual behaviours, and urine spraying was decreased, whereas hiding was increased, compared with cats that underwent gonadectomy at an older age^[103]. Among male and female cats that underwent early-age gonadectomy, shyness was increased^[103].

Within an urban unowned free-roaming cat population, TNR did not produce adverse effects on behaviours relating to social structure. Further, cats became less active, and urine spraying reduced significantly^[109]. Reduced aggression has been noted in free-roaming neutered, compared to sexually intact, males^[110].

Overall: Taken together there is no overwhelming case to neuter cats to improve their own welfare. The health benefits or disbenefits are rather evenly matched. Lower mortality rates are evident in neutered cats (which may be secondary to behavioural changes associated with less straying, fighting and risky behaviours) and some reduction in incidence of pyometra and mammary tumours in female cats. However, neutering also increases the risk of obesity and associated diseases, and surgical complications at the time of neutering. The main welfare benefit is to avoid over-population of cats and the welfare costs to the kittens and other cats, particularly in the unowned population.