A Contribution to the Discussion About Causes of Decreasing Fertility in Pugs

By Dr. Milan Raba, the President of the Mops Klub CR.

Recently we are increasingly becoming aware of the existence of a quite disturbing phenomenon which is the decreasing ability of bitches in our breed to become pregnant and carry pups for the full period of pregnancy, with the average number of pups in a litter also becoming rather small. The causes as discussed on the pages of Zpravodaj and on the Internet include, for example, bad timing for mating or bad health condition of either bitches or dogs, and so on. In my view, however, main cause of this disturbing situation had not as yet been discussed. The main cause, to my mind, is an overall lower vitality of the breed caused by increased inbreeding, with the long-established breeding practice of family and lineage selection resulting in the so-called 'inbreeding depression'. Although, fortunately, pure inbreeding (that is, for example, mating parents with their offsprings, or mating full sibs) is not the practice in this breed, the family/lineage selection, that is, the selection of offspring from both (male and female) lines with the same single ancestor, is in this country quite common. Anyone consulting pedigree of his/her pug will find that, to a great degree of probability, this is actually the case. What then are the dangers of the family/lineage selection which is certainly a well-tested method to strengthen certain desirable traits in breeds and which had been applied in dog and livestock breeding since the 19th century? According to the basic genetics it is well-known that all traits, and not necessarily only the obvious trait such as the colour of coat, but also the traits not apparent at the first sight such as metabolic processes or temperament tendencies, are dependent on genes which consist of pairs of allelomorphs. These allelomorphs are paired in either the dominant or recessive relation. For a recessive allelomorph to manifest its presence it must be present in duplicate (the homozygous state). This means that both allelomorphs must be recessive in order to display a trait or traits that are specifically coded by this arrangement of allelomorphs. (For further information see, for example, Smrckova-Raba, The Pugs, and the other authors, e.g. Dostal). As the family/lineage selection can serve to strengthen certain desirable traits in breeds, it may also result in manifestation of undesirable traits such as decreased ability of bitches to conceive or to lose their pups in the early stages of pregnancy with subsequent resorption of embryos (and so far we do not exactly know the cause of this). The danger of this happening is greater, the longer the family/lineage selection is practised. In terms of reproductive aspects of genetics, all animal species have a certain number of different allelomorphs that in natural environment can be freely combined as a result of mating. In this situation the combination of allelomorphs can be infinite while mutation may occur only very rarely. (Mutation = changing of genetic information as a result of, e.g. UV rays, etc.). In breeding pedigree dogs using family/lineage selection, we, however, tend to prefer individual offsprings with desirable external traits, i.e. desirable for showing purposes, with the intention being to concentrate or reduce the number of desirable allelomorphs available in order to affect positively the fixation of desirable external traits. The price to be paid for achieving this is that by suppressing or losing other desirable dominant allelomorphs we make it possible for 'genetic drift' to occur, i.e. we provide an opportunity for undesirable recessive allelomorphs (until then kept in check by the dominant allelomorphs) to manifest themselves. Undesirable recessive allelomorphs are especially those resulting in hereditary anatomic or health disorders (e.g. heart or kidney disorders) as well as metabolic disorders such as the sugars or albumin processing disorders. The other types of hereditary defects may also include deafness, blindness, albinism, and other defects. Many of the writers on the subjects agree that a loss of genetic variability is precisely what causes decreased vitality of a breed, which may be manifested not only by decreased fertility but also by impotency of dogs, defective maternal behaviour in bitches or lower average life-expectancy of the breed. The majority of breeders are familiar with beneficial effect of introducing 'fresh blood', i.e. introducing, for example, a completely unrelated breeding dog, to increase the vitality of the breed. This is known by a professional term as heterosis, meaning basically an introduction of 'new' allelomorphs within the population of the breed. In terms of reproductive aspects of genetics, it is the genetically effective, i.e. sexually active, part of the breed population that is important for the transmission of genetic information; i.e. that part of breed population producing offsprings and thereby passing on genetic information regardless of the actual size of the breed population as defined by the number of pedigrees issued. In theoretical case, a genetically effective part of a breed population consisting of two dogs and two bitches sexually active and producing 100 offsprings does not become 104 but, actually, only four of the sexually active animals, which means that allelomorphs of only those four are present in the population of this hypothetical breed X. Here, obviously, we must deal with the objection pointing out that a majority of pedigree breeds did come into existence as a result of relatively narrow family/lineage selection that would make the size of genetically effective population eventually as small as that of the hypothetical breed X above. Closing of registers of pedigree breeds, however, did not take place until early in the 20th century, which some of the more radical opposers of family/lineage selection refer to as 'shutting in a genetic ghetto'. Until that time dogs typical of the breed but without a pedigree were accepted for breeding and, similarly, crossbreeding with other breeds or crossing of two breeds were a common practice; this was, for example, the case of the Czech terrier which was produced relatively recently. These practices significantly extended the genetic pool or, in other words, increased the number of allelomorphs available for breeding program, and for most of the breeds this pool remained sufficient enough until very recently. At present, however, this genetic pool seems to be nearly empty. Despite nearly 1,000 years of existence as a breed, pugs remained relatively resistant to the effects of decreasing genetic variability. This is also a view of H. Wachtel, the eminent opposer of family/lineage selection, expressed in his book Dog Breeding in 2000. Their resistance is attributed to their continuing crossing with other breeds with short, but broad, skulls, such as the pekingese or other heterogeneous breeds of dogs of Chinese origin. It is said that long-haired pugs were still in existence in the 19th century. In fact, comparing pugs in the paintings of Goya (portrait of Marquise de Pontejos) or Bogart with our pugs in K. Dvur we are hesitant to see them as the dogs of the same breed; this shows how heterogeneous the population of pugs was. The present breed was also genetically revitalised by acquisitions and imports from China during the second half of the 19th century. For now, fortunately, pugs remain free of the problems affecting other breeds as a result of the narrow family/lineage selection such as, for example, Dalmatian (deafness, blindness due to problems with retina, stress on the spots, the 'merle' gene) or Bull Terrier (degenerative kidney problems, stress on egg-shaped head). These two breeds clearly demonstrate the dangers of narrow selection concentrating on a specific trait that may result in serious hereditary disorders. Pug, in my view, is also susceptible to hereditary disorders. There are cases of rare hereditary disorders (e.g. gall bladder problems) particularly in the USA where narrow family/lineage selection is quite common. These problems may often require complex and costly operations which may not be always successful. Also, what cannot be overlooked are the excessive demands of breeding for show purposes, with the stress on the subsequent commercial profit, which may lead to over-exaggeration of some specific traits of a breed and, subsequently, to hereditary health problems (e.g. eye or breathing problems). The relatively minor soft palate problem and the quite serious stifle joint problem (dislocation) are also considered hereditary conditions. Recently, many environmentalists, and biological scientists in the countries of the EU are increasingly using the term "tyranny of breeding'. By this they mean accumulation of hereditary defects and extreme intensification of typical hereditary traits in a breed to such a degree that it results in deterioration of health condition of an individual pedigree animal. The term had been taken up by the media and eventually it became a topic of debate in the European Parliament, so much so that the attempts to introduce legislation to regulate selection programs of particular breeds are becoming increasingly noticeable. What is more, Pug had been included among those particular breeds. FCI's response to these attempts was to introduce a breeding program for selection of genetically sound populations of dog breeds. Unfortunately, response to this program was rather lukewarm in this country, with many, apart from some exceptions, failing to realise the importance of such a program. Adopting this program does not mean that we should go back to some primeval dog breed but to provide conditions for breeding animals with typical traits yet healthy, without suffering from any hereditary defects. Breeding experts and responsible breeders will all be required to deal with the problem of how to produce physically and genetically sound offsprings while retaining all the typical traits of a breed. To find solution to this key breeding problem in the 21st century will be difficult but it is possible. How to maintain both the genetic variability and vitality of the breed without significant deterioration in the standards of external appearance of the breed? In the first instance we should be looking at how many individual animals there are in the breed that are actually active and, therefore, genetically effective with the breed population. What we will find is that in the breed there are just 5-10 breeding dogs and only slightly larger number of bitches producing huge majority of offsprings for a specific 5-year period. This generation of offsprings will be undoubtedly very attractive in their external appearance as well as successful in dog shows. Many of their offsprings will be also undoubtedly of a very high quality but what do we know how many of those of low quality there might be? There are still no statistics of the frequency of hereditary defects and this certainly does not really make a contribution to the reputation of the Pug Club.

o It is therefore essential to enlarge genetically effective population of our pugs in the future through, for example, restricting the number of mating by pedigree dogs in a year, thereby providing more opportunities for other breeding dogs to produce offsprings; this is the practice currently adopted in some breeds of hunting dogs in this country.

o It is essential to prevent repetitive mating of the same breeding animals, event though their offsprings might be most attractive for showing purposes.

o Do not prevent but allow mating of the black and beige pugs; this cannot, in my opinion, threaten the density of black colouring in offsprings.

o Do not allow mating of animals to prevent occurrence of a common ancestor on both sides of their pups within a specific number of generations. Acceptable would be a common ancestor in the third generation on one parental side and in the fourth generation on the other parental side.

o To support foreign imports for more distant countries, e.g. from Finland, but also from Japan or China (i.e. transporting frozen semen?). It will be, however, absolutely essential to have full pedigree details.

I see the main task of the Pug Club CR in ensuring the future of the breed that is healthy and full of vitality. It should be our responsibility given the breed's history and we should also feel the same responsibility towards all prospective dog owners who should rightfully expect their pugs to be healthy and to fully enjoy the pleasure that these unique dogs are able to give to all who understand them.

Questionnaire analysis of the state of health of the pug population in Bohemia and Moravia

I. Purpose of the analysis

The Purpose of the analysis was to ascertain the incidence of the most common diseases of pugs whose owners are members of the Pug Club of the Czech Republic. The work was based on the fact that no similar work has been undertaken in the Czech Republic, and as far as we know, has not been done for other breeds. Our inspiration for the analysis was in particular the results of a similar survey undertaken in Canada, which were published on the Internet and in shortened form in Newsletter no. 4/98. (Reid K., Pug Health Survey, June 1,1998 , http:/members.tripod.com./~solnapug/survey results.htm.)

In order to be able to undertake essential health care measures in animal keeping, it is first necessary to know the real health situation in the Czech pug population, and to know as exactly as possible the incidence of particular individual ailments and defects. The questionnaires were part of Newsletter no. 4/98 which is sent out to all members of the Pug Club, which means that it was received by a total of 295 members of the Pug Club. The questionnaire was anonymous, so that it was not necessary to give the name either of the owner, the dog or the breeding kennel; in this way the information given could not be misused. The respondents market answers either Yes or No, and were able to add explanatory comments. The investigation examined in particular diseases and defects presumed to be typical overall for pugs and other short-headed or small breeds.

II. Characteristics of the sample

As already mentioned, all members of the Pug Club of the Czech Republic were approached, based on the membership list which received Newsletter no. 4/98. Completed questionnaires were received for 45 pugs in total, of which 24 were dogs and 21 bitches, 36 beige, 9 black

III. Results

Affected by groups of organs:

IV. Commentary

It is a pity that in the end relatively few of pug owners replied. This obviously lowers the statistical significance of the findings. This does not, however, mean that the data gathered are not important. Apart from the Canadian author already referred to, I am not aware that work specifically targeted at one breed and at such depth has been published. It is first in the literature in Czech.

The high percentage suffering from skin disorders, diseases of the respiratory tract and affected by ear and eye problems does not come as a surprise. Dental problems and skin disorders can to a large extent be prevented by timely prevention. The same applies to ear disorders, where almost all the cases concerned infection of the ear canal, which can be prevented with appropriate care and is treatable if diagnosed in time. Nearly one third of the pugs studied had eye problems linked for the most part with traumatic states and their consequences; this is a very high number even when allowing for the fact that pugs' eyes are known as a problem area from the point of view of possible damage. A quarter of the pugs had or have breathing problems, which can also be considered a relatively high number. In contrast to breathing problems arising from natural causes, the frequency of eye disorders can be lowered by breeders and owners giving sufficient attention to the prevention of eye injuries. More than 5 pugs or one-tenth of the sample has stretching of the soft palette. In view of the fact that this is for the most part an hereditary problem this number may be considered to be significant and demands the attention of both breeders and breeding experts. Problems with movement covered shoulder joint 1x, diskopathy 2x, luxation of the patella in three cases. There was not a single case of luxation of the hip joint. Nor thankfully was there a single case recorded of PDS (pug brain infection).

Comparison with Canadian data:

Fonte: Mops Klub CR (http://www.mopsklub.cz/vet.htm)