Assessing the impact of breeding strategies on inherited disorders and genetic diversity in dogs

Evaluation of breeding strategies to reduce the inbreeding rate in the Friesian horse population: Looking back and moving forward

In the past, small population sizes and unequal ancestor contributions have resulted in high inbreeding rates (ΔF) in the Friesian horse. Two decades ago, the studbook implemented a mating quota and started publishing individual kinships and reduced ΔF below 1% per generation. However, since then, the breeding population size has decreased and this raises the question whether current breeding strategies are sufficient to keep ΔF below desired rates. The aim of this study was to (1) reflect on past inbreeding trends and their main determinants, using pedigree analysis and (2) evaluate the effectiveness of the current and additional breeding strategies using stochastic simulations. We estimated the current ΔF (2013-2022) at 0.72% per generation. While the total contribution of the top 10 sires to the number of offspring per year has decreased from 75% in 1980 to 35% in 2022, this was mainly due to an increased number of approved studbook sires, and not due to more equalized contributions among sires. Of the simulated breeding strategies, selecting only breeding stallions with a below average mean kinship (i.e., "mean kinship selection") was most effective to decrease ΔF (from 0.66% to 0.33%). Increasing the number of breeding sires only had an effect when also a mating quota was applied. However, its effect remained limited. For example, a ~1.5 fold increase, combined with a mating quota of 80 offspring per sire per year, reduced ΔF from 0.55% to 0.51%. When increasing the number of breeding mares, a practically unfeasible large increase was needed for a meaningful reduction in ΔF (e.g. twice as many mares were needed to reduce ΔF from 0.66% to 0.56%). Stratified mating quotas, a novel approach in which we assigned each sire a mating quota (of 60, 80, 100 or 120 offspring per year) based on its mean kinship to recently born foals, resulted in a lower ΔF (0.43%) than a general mating quota of 90 offspring per sire per year (0.55%). Overall, while the current ΔF is below 1%, we recommend to implement additional strategies to further reduce ΔF below 0.5% in the Friesian horse population. For this breed and similar populations, we recommend to focus on breeding strategies based on kinship levels to effectively reduce ΔF.

Ethics in canine reproduction - a survey among veterinarians who provide canine reproductive services

OBJECTIVE

Several dog breeds suffer from health and welfare problems due to unfavorable anatomies and high prevalence of inherited diseases. Veterinarians should care for animal health and welfare but they may also be involved in breeding management including the use of reproductive techniques.

MATERIAL AND METHODS

An online survey was conducted to find out how veterinarians who are involved in small animal reproduction regard ethical issues, which services they provide, how they discuss and handle ethical concerns and talk about them with breeders.

RESULTS

In total, 83 participants mainly from Europe completed the online survey. Opinions on which interventions are ethical or not were heterogeneous. Most respondents (79.2 %) found it ethical to perform artificial insemination (AI) in dogs which did not reproduce naturally before. However, 62.7 % of participants stated that surgical insemination is not ethical. Elective cesarean sections are considered not ethical by approximately half of the participants. A closer look at responses to the questions of whether AI is ethical under specific conse quences suggests that most veterinarians are making ethical and value judgments in terms of what is justifiable or not. However, more than 80 % feel at least sometimes compromised by ethical conflicts.

CLINICAL RELEVANCE

This research intended to foster discussion of this topic. International strategies should be developed to support solving conflicts and dilemmas related to ethical issues in dog breeding and assisted reproduction, as well as diminishing physical disabilities and heritable diseases.

Veterinarians' Competence in Applying Basic Genetic Principles and Daily Implementation of Clinical Genetics: A Study in a University Environment

Veterinarian competency in genetics is vital for a meaningful application of the rapidly growing number of genetic tests available for animals. We evaluated the use of genetic tests in the daily veterinary practice and the competency of university-employed veterinarians in applying basic principles of genetics in a clinical setting through an electronic survey with 14 cases and 7 statements on genetics. Ninety-one non-geneticist veterinarians from two veterinary faculties in two different countries responded. Almost half of the participants apply genetic tests during their daily work, with frequencies varying between weekly and once a year. The most common indication to request a genetic test was diagnostic testing of clinically ill patients. Although 80% of the veterinarians communicated the result of a genetic test themselves, only 56% of them found it "very to rather easy" to find the correct test, and only 32% of them always felt competent to interpret the result of the test. The number of correctly answered questions varied widely, with median scores of 9/14 (range 0-14) and 5/7 (range 0-7) for the cases and statements, respectively. Most difficulties were seen with recognition of pedigree inheritance patterns, while veterinarians scored better in breeding advice and probability of disease estimations. Veterinarians scored best on questions related to autosomal recessive inheritance, followed by complex, autosomal dominant, X-linked recessive, and X-linked dominant inheritance. This study exposed pain points in veterinarians' knowledge and has led to the formulation of recommendations for future education and communication between laboratories, geneticists, and veterinarians.

Inbreeding levels in an open-registry pedigreed dog breed: The Australian working kelpie

The depletion in genetic diversity of closed-pedigree dog breeds can be a contentious topic and can lead to calls for open-registry. However, strong evidence in support of proposed open-registry solutions is lacking, with the reproductive isolation of these breeds unlikely to be the sole cause of elevated inbreeding levels. Human-induced limitations, such as popular sire effects, are unlikely to be confined to closed-registry breeds and conceivably play an important role in maintaining genetic diversity within all breeds. Consequently, the aim of the current study was to explore inbreeding levels in an open-registry breed and determine the impact open-registry has on genetic diversity. Complete pedigree records on all Australian working kelpies (AWKs) were provided by the Working Kelpie Council with the cleaned pedigree consisting of 86,671 individuals with a median pedigree depth of 6.6 generations. The average inbreeding coefficient in the AWK population was 0.049 with an increase in inbreeding coefficient of 0.0016/year. This demonstrates that opening a breed registry can have a beneficial impact on the level of inbreeding within a population over the longer-term. However, allowing for a generation length of 5.1 years yielded an effective population size of 61 for AWKs and demonstrated a pattern consistent with closed-registry dog populations of comparable size.

The dog 2.0: Lessons learned from the past

In recent years, concerns have been raised on the diversity, health and welfare of our (pedigree) dog population. Somewhat justified, the popular sire effect, population bottlenecks, the founder effect and inbreeding have left their marks on the dog as we know it. In order to improve the health and welfare of the canine population in general, individual breeding programs should adhere to the concept of ethical breeding (i.e. "the use of healthy animals true to their species in behaviour and looks, and when applicable, showing a sustainable performance") when population-specific breeding goals are defined. Even though every population has its own problems, the approach to get to possible solution(s) is similar. The starting point will always be the identification of which (un)desirable pheno- and genotypes are segregating and what their prevalence is, followed by an evaluation of the genetic diversity. Based on that information and, when applicable, additional criteria like breed standards, breeding goals can be defined. It is of critical importance that these goals are put forward with a long term vision in mind and with consensus from the stakeholders to ensure collaboration. Upon prioritization of the most important goals, when necessary with the help of specifically developed tools, the final step is choosing the most optimal combination of breeding strategies. This paper aims to provide a stepwise approach to identify and tackle population-specific problems encountered in breeding programs.

Assessing the relative importance of health and conformation traits in the cavalier king Charles spaniel

Background

The selection of a future breeding dog is a complicated task, in which disease characteristics and different traits have to be combined and weighed against one another. Truncation selection, that is the exclusion of affected animals, may be very inefficient when selecting on a large number of traits, and may result in a reduction of the genetic diversity in a population or breed. Selection could be facilitated by the use of a selection index that combines multiple traits or breeding values into one score. This however requires a consideration of their relative value according to their economic weight, which is difficult to express in monetary units for health traits. The use of a choice experiment to derive non-market values might be a solution to this problem. This is a pilot study to assess the potential use of choice experiments to ascertain the public preference and relative importance attached to health- and conformation traits in the selection of a Cavalier King Charles spaniel. The focus was on two prevalent disorders, mitral valve disease and syringomyelia, and on several important conformation traits such as muzzle length and eye shape. Based on available prior information, a Bayesian D-optimal design approach was used to develop a choice experiment and the resulting choice sets.

Results

Every participant (breeder or owner) in the choice experiment was presented with a total of 17 choice sets, in which at most four traits could vary to reduce the cognitive burden. A total of 114 respondents participated in the choice experiment and results showed that respondents (breeders/owners) current attitudes were directed towards health (syringomyelia and mitral valve disease), followed by eye shape and level of inbreeding.

Conclusions

This approach identifies the value breeders and owners attach to certain traits in the breeding objective. The resulting relative weights, represented as the logworths obtained from the choice experiment, could be an alternative to economic weights. They could be implemented as a weight when breeding values are available, but more study on this topic will be necessary. A challenge in this approach is to scale up the experiment with additional traits. Moreover, for other traits, the genetic parameters and correlations should be known first, in order to include them in the health selection index as well.

Moving from information and collaboration to action: report from the 3rd International Dog Health Workshop, Paris in April 2017

BACKGROUND

Breed-related health problems in dogs have received increased focus over the last decade. Responsibility for causing and/or solving these problems has been variously directed towards dog breeders and kennel clubs, the veterinary profession, welfare scientists, owners, regulators, insurance companies and the media. In reality, all these stakeholders are likely to share some responsibility and optimal progress on resolving these challenges requires all key stakeholders to work together. The International Partnership for Dogs (IPFD), together with an alternating host organization, holds biennial meetings called the International Dog Health Workshops (IDHW). The Société Centrale Canine (French Kennel Club) hosted the 3rd IDHW, in Paris, in April, 2017. These meetings bring together a wide range of stakeholders in dog health, science and welfare to improve international sharing of information and resources, to provide a forum for ongoing collaboration, and to identify specific needs and actions to improve health, well-being and welfare in dogs.

RESULTS

The workshop included 140 participants from 23 countries and was structured around six important issues facing those who work to improve dog health. These included individualized breed-specific strategies for health and breeding, extreme conformations, education and communication in relation to antimicrobial resistance, behavior and welfare, genetic testing and population-based evidence. A number of exciting actions were agreed during the meeting. These included setting up working groups to create tools to help breed clubs accelerate the implementation of breed-health strategies, review aspects of extreme conformation and share useful information on behavior. The meeting also heralded the development of an online resource of relevant information describing quality measures for DNA testing. A demand for more and better data and evidence was a recurring message stressed across all themes.

CONCLUSIONS

The meeting confirmed the benefits from inclusion of a diverse range of stakeholders who all play relevant and collaborative parts to improve future canine health. Firm actions were set for progress towards improving breed-related welfare. The next international workshop will be in the UK in 2019 and will be organized by the UK Kennel Club.

Genetic management of Dutch golden retriever dogs with a simulation tool

Excessive inbreeding rates and small effective population sizes are an important problem in many populations of dogs. Proper genetic management of these populations can decrease the problem, and several measures are available. However, the effectiveness of these measures is not clear beforehand. Therefore, a simulation model was developed to test measures that aim to decrease the rate of inbreeding. The simulation program was used to evaluate inbreeding restriction measures in the Dutch golden retriever dog population. This population consisted of approximately 600 dams and 150 sires that produce 300 litters each year. The five most popular sires sire approximately 25% of the litters in a year. Simulations show that the small number of popular sires and their high contribution to the next generation are the main determinants of the inbreeding rates. Restricting breeding to animals with a low average relatedness to all other animals in the population was the most effective measure and decreased the rate of inbreeding per generation from 0.41 to 0.12%. Minimizing co-ancestry of parents was not effective in the long run, but decreased variation in inbreeding rates. Restricting the number of litters per sire generally decreased the generation interval because sires were replaced more quickly, once they met their restriction. In some instances, this lead to an increase in inbreeding rates because the next generations were more related. The simulation tool proved to be a powerful and educational tool for deciding which breeding restrictions to apply, and can be effective in different breeds and species as well.

Recent breeding history of dog breeds in Sweden: modest rates of inbreeding, extensive loss of genetic diversity and lack of correlation between inbreeding and health

One problem in modern dogs is a high occurrence of physical diseases, defects and disorders. Many breeds exhibit physical problems that affect individual dogs throughout life. A potential cause of these problems is inbreeding that is known to reduce the viability of individuals. We investigated the possible correlation between recent inbreeding and health problems in dogs and used studbook data from 26 breeds provided by the Swedish Kennel Club for this purpose. The pedigrees date back to the mid-20th century and comprise 5-10 generations and 1 000-50 000 individuals per pedigree over our study period of 1980-2010. We compared levels of inbreeding and loss of genetic variation measured in relation to the number of founding animals during this period in the investigated dog breeds that we classified as 'healthy' (11 breeds) or 'unhealthy' (15) based on statistics on the extent of veterinary care obtained from Sweden's four largest insurance companies for pets. We found extensive loss of genetic variation and moderate levels of recent inbreeding in all breeds examined, but no strong indication of a difference in these parameters between healthy versus unhealthy breeds over this period. Thus, recent breeding history with respect to rate of inbreeding does not appear to be a main cause of poor health in the investigated dog breeds in Sweden. We identified both strengths and weaknesses of the dog pedigree data important to consider in future work of monitoring and conserving genetic diversity of dog breeds.