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Statistical analysis in support of maintaining a healthy traditional Siamese cat population Arthur M. A. Pistorius, Ineke Blokker To cite this version: Arthur M. A. Pistorius, Ineke Blokker. Statistical analysis in support of maintaining a healthy tra- ditional Siamese cat population. Genetics Selection Evolution, BioMed Central, 2021, 53 (1), pp.6. 10.1186/s12711-020-00596-w. hal-03105257 HAL Id: hal-03105257 https://hal.archives-ouvertes.fr/hal-03105257 Submitted on 11 Jan 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Pistorius and Blokker Genet Sel Evol (2021) 53:6 https://doi.org/10.1186/s12711-020-00596-w Genetics Selection Evolution RESEARCH ARTICLE Open Access Statistical analysis in support of maintaining a healthy traditional Siamese cat population Arthur M. A. Pistorius1,2* and Ineke Blokker2 Abstract Background: For many years, breeders of companion animals have applied inbreeding or line breeding to trans- fer desirable genetic traits from parents to their ofspring. Simultaneously, this resulted in a considerable spread of hereditary diseases and phenomena associated with inbreeding depression. Results: Our cluster analysis of kinship and inbreeding coefcients suggests that the Thai or traditional Siamese cat could be considered as a subpopulation of the Siamese cat, which shares common ancestors, although they are con- sidered as separate breeds. In addition, model-based cluster analysis could detect regional diferences between Thai subpopulations. We show that by applying optimal contribution selection and simultaneously limiting the contribu- tions by other breeds, the genetic diversity within subpopulations can be improved. Conclusion: In principle, the European mainland Thai cat population can achieve a genetic diversity of about 26 founder genome equivalents, a value that could potentially sustain a genetically diverse population. However, reach- ing such a target will be difcult in the absence of a supervised breeding program. Suboptimal solutions can be obtained by minimisation of kinships within regional subpopulations. Exchanging animals between diferent regions on a small scale might be already quite useful to reduce the kinship, by achieving a potential diversity of 23 founder genome equivalents. However, contributions by other breeds should be minimised to preserve the original Siamese gene pool. Background Closer to home, this also applies to the breeding of Worldwide, there is growing concern about the loss domestic animals and companion animals. For many of biodiversity, which is caused by the ever-increasing years, inbreeding has been an accepted method to trans- human population. Te quantitative reduction of bio- fer desirable genetic traits to the ofspring in a predict- topes and over-exploitation of wild species result in the able way, thereby increasing the economic or aesthetic fragmentation of populations and reduction in their sizes value of the animals. However, this approach that delib- which, in turn, increase the degree of inbreeding. Finally, erately reduces the heterozygosity level, simultaneously inbreeding may result in inbreeding depression, which increases the risk of combining deleterious genes, and manifests itself by reduced reproductive ftness and thus results in increasing the prevalence of several hered- reduced ability to adapt to changing environmental con- itary diseases or inbreeding depression which negatively ditions. All these factors negatively infuence the possibil- infuence the health of the animals and the population at ity to restore the size of populations to a reasonable level. large. Tus, the risk of extinction increases [1]. Te Siamese cat is a very ancient breed that originated from the Kingdom of Siam (nowadays Tailand), and was *Correspondence: [email protected] already known in the 14th century [2]. Te breed was 2 Workgroup Traditional Siamese Cat Breeders in The Netherlands (WTSN), imported into the United Kingdom in the late 19th cen- NL-1815 HC Alkmaar, The Netherlands tury and then spread to other European countries. Start- Full list of author information is available at the end of the article ing in the mid-20th century, Siamese cats that exhibited a © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creat iveco mmons .org/licen ses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creat iveco mmons .org/publi cdoma in/ zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Pistorius and Blokker Genet Sel Evol (2021) 53:6 Page 2 of 12 very slender body and wedge-shaped head conformation Oriental Shorthairs (EMS code: OSH) and 737 Balinese became fashionable. Te classical shaped cats were not (EMS code: BAL) cats, excluding unspecifed variants registered or accepted for shows anymore, which almost of these breeds. Te remaining 625 entries are from 25 led to extinction of the original type in Europe. other breeds, which were used shortly after the Second A few breeders started to re-introduce the classical World War to rebuild the feline livestock and to create type and, in 1995, the traditional Siamese was once again new breeds such as the Oriental Shorthair [2]. After 2000, accepted by some registries. Te new population was active data collection on non-Tai breeds was stopped, built on founders that were imported from several coun- except for animals which were related to the Tai, e.g. in tries around the world, and on selected Siamese cats of the case of occasional outcrossing with Siamese cats. European origin, which had a less extreme conformation. Te data collection is known to be incomplete for the Te registered breed name Siamese remained connected periods after the Second World War, when the registries to the modern type and from that time on, the classical had to be rebuilt, and towards the end of the 20th cen- type became known as the Tai cat, but this defnition is tury when the traditional Siamese cats were not accepted not accepted worldwide. In the United States of Amer- anymore for registration or for entering shows, since they ica, the most important registry, the Cat Fanciers’ Asso- did not meet the new breed standards. Te percentage of ciation (CFA), does not recognise the Tai as a breed unknown parentage is about 9 %. [3] whereas Te International Cat Association (TICA) Te database of the CFA Siamese Breed Council [6] defnes the Tai as a contemporary cat, which has proven lists 49 animals that were imported from Tailand, to be directly imported from Tailand [4]. Hong Kong or India in the early 20th century and can be Meanwhile, heavy selection pressure and misfortunate regarded as the founders of the European Siamese and outcrosses with other breeds resulted in an increased Tai population. Te most distant founder was traced prevalence of several hereditary diseases within the con- more than 50 generations back. Te average equivalent temporary Siamese cat population, e.g. progressive retina complete generations of the current Tai cat population atrophy (PRA) [5] and traits which are associated with is 12.3. After 20 generations, the percentage of pedigree inbreeding depression such as skeletal deformations and completeness is 21 % (Additional fle 2). a reduced life span. In contrast, up to date, the Tai cat Since subsequent generations show a strong overlap population is essentially free from the hereditary diseases and full demographic details are not available, through- that have been detected within the contemporary Sia- out this work we defne a population as the parents of the mese breed except for isolated cases. Tus, the Tai and kittens, born in two consecutive years. the Siamese cat populations appear to have developed diferently. In this article, we report on the historic develop- Defnitions ment and present status of the genetic diversity within In this work, we base our results on the concept of mean the Siamese and Tai cat breeds that are present on the kinship as developed by Ballou [9] and Lacy [10]. Te European mainland. We carried out a cluster analysis mean kinship is the mean of all pairwise kinship coef- to reveal the relationships between both breeds and to cients between an individual and all other breeding ani- explore regional diferences in the distribution of their mals, including itself, according to: genetic diversity. We also calculated the mean kinship 1 N of breeding animals per cluster, which provides a more mk = f . i N ij (1) useful parameter to maintain or improve genetic diver- j=1 sity within the current Tai breed. Our aim is to pre- serve a healthy cat population without any exaggeration Te individual pairwise kinship coefcients, fij , are in appearance and that is related to the original Siamese derived from the pedigrees, using the tabular method cats that were present in Europe until about 1970.

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