Selective Breeding

Chapter 7
Selective Breeding


Co-author: Brenda Bonnett BSc, DVM, PhD, Consulting Epidemiologist


B Bonnett Consulting, Wiarton, Ontario, Canada



  1. 7.1 Introduction
  2. 7.2 Selective Breeding of Dogs and Cats
  3. 7.3 Effects of Pedigree Breeding and Breed Standards on Welfare
  4. 7.4 Ethical Perspectives on Breeding
  5. 7.5 Possible Practical Solutions to Breeding of Healthier Cats and Dogs

7.1 Introduction


In August 2008, the British television channel BBC1 aired ‘Pedigree Dogs Exposed’, a documentary on the breeding of pedigree, purebred dogs. This documentary alleged that selective breeding of pedigree dogs in the United Kingdom was highly detrimental to their health and welfare. The Kennel Club, a leading British organisation in charge of dog shows, which maintains a registry for pedigree dogs (see Chapter 1), was the chief target of the criticism. The documentary gave many examples of the negative effects of current breeding practices on a wide variety of dog breeds. One of many troubling examples was a Cavalier King Charles Spaniel that showed behaviour suggestive of severe pain, due to a condition known as syringomyelia, which occurs when the skull is too small for the brain, a likely consequence of pursuing a specific flat skull shape as a breeding goal (see Figure 2.2b).


For the general public, this BBC documentary came as a shock. However, experts within the field recognised that a number of valid issues were raised: a growing body of literature had already documented the negative effects of genetic selection on the health of dogs and cats (see, e.g. CAWC, 2006; McGreevy & Nicholas, 1999).


The selective breeding of dogs and cats, of course, also has a positive side. Selective breeding maintains a diversity of breeds. In the case of dogs, the wide variation across breeds in appearance, temperament, function and utility is a factor in human–dog interactions. At least anecdotally, it is clear that people show intense and often lasting affinity for specific breeds. Through selective breeding, breeds and individual dogs have been created with remarkable abilities and characteristics (assistance dogs, tracking and rescue dogs, hunting dogs, etc.), and selective breeding has been used to eliminate specific diseases or reduce their prevalence (e.g. Canine Leukocyte Adhesion Deficiency (CLAD), a fatal immunodeficiency disease in Irish Setters).


However, these benefits do not eliminate the ethical issues raised by the selective breeding of purebred dogs and cats, on which we will focus in this chapter. We will begin by describing how the selective breeding of purebred dogs and cats is organised. After that, we will present what is known about the effects of breeding on animal welfare, with a focus on the negative effects on the health of purebred dogs and cats. We will then consider the issue from different ethical perspectives; finally, we will look at possible practical solutions to the problems.


7.2 Selective Breeding of Dogs and Cats


Domestication of dogs and cats goes back many thousands of years, although the precise nature and timing of the domestication of the two species is contested. Selection of dogs for specific purposes and the existence of dog ‘breeds’ also have a long history. However, the establishment of purebred dogs and cats based on pedigrees – that is, where breed ancestry is recorded – is relatively recent. Most of the common dog and cat ‘pure breeds’ have been established within the last 200 years, as has the system based on organisations that keep breeding records and organise dog and cat shows, as we saw in Chapter 1. Most modern dog and cat breeds have been established from a limited number of individuals, and only descendants of these individuals can count as belonging to a given breed – with a few exceptions, no new genes have been deliberately added after a breed has been established.


The dog population in the Western world can be divided into four groups: purebred pedigree dogs; dogs that are purebred and belong to a specific breed but that lack a pedigree; so-called designer breeds that are selectively bred crosses between one or more breeds; and random or accidental crosses between breeds. In the United States, approximately half the dogs are purebred (AVMA, 2012), whereas in European countries such as Germany and Denmark over three-quarters are reported to be purebred (Proschowsky, Rugbjerg & Ersbøll, 2003; Switzer & Nolte, 2007). Although statistics vary by country, only a minority of purebred dogs have a registered pedigree, and the proportion is falling. Designer breeds are a recent phenomenon, and anecdotal reports in both North America and Europe indicate that the numbers are rising rapidly, with many being sold for prices equal to or surpassing those of pedigree dogs.


It is generally accepted that dogs of specific breeds are relatively predictable in terms of temperament and behaviour (although because environmental factors are important too, the predictability may in specific cases be limited). Other factors, such as the level of grooming needed, are also breed specific. So, when people buy a dog or cat of a certain breed they can, to some degree, predict what kind of animal they will get, provided that they do their homework (although, unfortunately, many people do not). However, the natures of crossbred dogs and especially randomly bred dogs are less predictable, and this may have implications for the relation between the animal and the owner. There is some evidence, for instance, that crossbred dogs are more often euthanased for behavioural reasons than purebreds (Mikkelsen & Lund, 2000), although of course many other factors could be involved (e.g. the cost of the purebred dog).


In some developing countries, there are also large populations of street dogs that, although not commercially bred, share certain phenotypic, ‘breed-like’, characteristics. This resembles the situation of the majority of companion cats in developed countries, which are not purebred but share certain ‘breed-like’ phenotypic characteristics, generally being termed domestic shorthairs (‘moggies’ or ‘country cats’). However, there are of course also pedigree purebred cats, and we discuss these in the following sections.


7.3 Effects of Pedigree Breeding and Breed Standards on Welfare


In the Western world, the breeding of pedigree show dogs and cats follows breed standards, defined and to variable degrees controlled by breed clubs. Breed clubs are often organised nationally – famous examples are the UK Kennel Club and the American Kennel Club – and may belong to larger international organisations.


Breed standards, with some local variations, currently exist for around 400 dog breeds and 40 cat breeds. Show dogs and cats are assessed by judges, appointed by the various mentioned organisations and clubs, who in turn decide how well the animals meet breed standards. Highly ranked dogs and cats will typically be used for breeding, so the opinions of show judges will have a significant effect on pedigree purebred animals, which may then trickle down to non-pedigree purebred animals.


The clubs may also set up restrictions on breeding, for example, requiring a certain outcome of a specific health test to allow an animal to be used for breeding, or making recommendations regarding norms of good breeding. However, there is often significant controversy and disagreement between breeders on the need for, and content of, breeding restrictions and recommendations.


Large numbers of apparently purebred dogs without pedigrees (recognised as specific breeds based on conformation) are also selectively bred by commercial breeders who are minimally influenced by the opinion of show judges or registry bodies. Instead, market forces drive these activities; and market forces in turn are heavily influenced by the media. An example of this is the partly celebrity-driven popularity of extra-small varieties of dog breeds such as Chihuahuas, so-called teacup or handbag dogs.


Breed standards are normally fixed, but over time their interpretation nonetheless shifts, as shown by the following three pictures of typical male German shepherds (Alsatians) spanning the period from 1910 until today. The phenotype of the ‘ideal’ German shepherd dog has changed gradually – but with dramatic effect – for example, in terms of a more sloping croup (hindquarters) (Figure 7.1)

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Figure 7.1 Male German Shepherds (Alsatians) at different times. (a) Tell von der Kriminalpolizei SZ 8770, who became a German winner in 1910. (Rasmussen & Bertelsen, 1980.) (b) Quax vom Aegidiendamm, a highly successful Danish show dog from the early 1970s.


(Reproduced with permission from O.B.C. Christensen.) (c) A typical modern male show dog. (Nikolai Tsvetkov/Shutterstock.com.)


Such changes in conformation (influenced by breed standards, and interpreted by show judges and breeders in the light of fashion) can have significant impacts on the welfare of the animals concerned. German Shepherds, for instance, are predisposed to hip dysplasia; and they have a higher risk of dying (or being euthanased) for conditions affecting locomotion compared to all other breeds, combined (Vilson et al., 2013). These effects on the health of the dogs may to a large extent be due to the heavily sloping croup (though the evidence here is not conclusive) (Wahl et al., 2008).


Selective breeding of dogs and cats based on their performance in dog or cat shows is an engaging hobby for many people, and in this sense, contributes to human welfare. Those involved in the world of pedigrees may be intensely committed to their breed, and perceive the protection and propagation of the breed as essentially preserving a valuable cultural heritage (see more on this below).


On the other hand, producing pedigree, purebred dogs and cats also has a number of negative consequences, both on the welfare of the animals, and on the well-being, quality of life, and finances of their owners. These problems can be aggravated when purebred dogs are produced not by hobby or show breeders, but by high volume commercial or incompetent backyard breeders (see more on this in Chapter 6).


The potential negative effects of breeding of purebred dogs and cats fall into three groups: breeding extreme phenotypes, which, as a direct consequence, create health and welfare problems; increased prevalence of diseases not directly linked to the phenotypes being selected; and increased prevalence of behavioural problems.


First, then: extreme phenotypes. We have already noted that Cavalier King Charles Spaniels can suffer from syringomyelia, on account of being bred for a flat skull: a 2011 study (Parker et al., 2011) found that by the age of 72 months, 70% of Cavalier King Charles Spaniels have asymptomatic syringomyelia (though it is a matter of debate to what extent the number of ‘asymptomatic’ carriers of a condition can serve as a predictor of the prevalence of the condition). Equally, it is suspected that the sloping croup of the German Shepherd breed will, as mentioned, predispose it to various problems. Another group of common phenotypes linked to severe health and welfare problems are the brachycephalic breeds of cats and dogs. ‘Brachycephalic’ means having a relatively broad, short skull, as seen in breeds such as Bulldogs, Pekingese, Pugs and Persian cats, which have been selected by humans, directly and indirectly, for their short faces and flat heads.


One prominent example of a brachycephalic breed is the English Bulldog. At the beginning of the nineteenth century, the bulldog was a working dog, used in the now universally illegal blood sport of bull baiting. When the sport was banned in the United Kingdom in 1835, bulldogs began to be bred in ways that radically changed both their character and appearance to enhance their desirability as companions. One of the most dramatic effects was a significant change in the dog’s facial structure: the upper jaw and skull were reduced in length, whereas the lower jaw remained relatively unchanged (Thomson, 1996). Unfortunately, the soft tissues of the face and mouth did not shrink sufficiently to adapt to the reduced space. As a result, the redundant soft tissues can cause partial obstruction of the nose and upper airways, making it difficult for the dogs to breathe: a condition known as brachycephalic obstructive airway syndrome (BOAS).


A recent study by Packer et al. (2013) showed that dogs with shorter muzzles are at higher risk of suffering BOAS – so selecting for a short nose is directly linked to increased levels of this disorder. Purebred cats with short noses also suffer from much higher levels of BOAS. Dogs with BOAS may be short of breath, snore, wheeze, gag, regurgitate and vomit (Packer, Hendricks & Burn, 2012), and the symptoms may become so severe that some dogs require surgical treatment. These difficulties are not only confined to English Bulldogs. A recent Danish study (Sandøe et al., 2013) reports that 6.2 % of Pugs, 5% of French Bulldogs, and 3% of English Bulldogs among non-referred patients at the University of Copenhagen Small Animal Veterinary Hospital in 2012 had undergone surgery for BOAS. Based on Packer, Hendricks & Burn (2012), there is reason to think that this is only the tip of the iceberg. The latter study documents that 58% of owners of dogs diagnosed with BOAS by vets claimed that their dog did not have, or had not had, breathing problems. The authors of the study infer from this that owners of the dogs in question view breathing problems as normal for the breed. This is also in line with the fact that snoring or grunting sounds are often mentioned as characteristic traits of Bulldogs, Pugs and similar breeds.

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Feb 16, 2017 | Posted by in GENERAL | Comments Off on Selective Breeding
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