ICB Podcast

Influence of genetics and inbreeding on disease (Woolliams 2012)

In this enlightening episode, we delve into the world of cattle genetics and disease. Most examples are for livestock, but the principles apply to breeding all animals, including dogs. Discover the complexities of the 'curse of the recessive' and learn how modern genomic tools are revolutionizing livestock management, offering new ways to identify and manage genetic defects and improve disease resistance. From understanding effective population size in breeds like the Holsteins to the role of Estimated Breeding Values (EBVs) and genomic technologies, we explore the transformative potential of genetic research in livestock breeding and disease control.

Join us as we unravel how genetics plays a critical role in managing disease. Whether you're a breeder, farmer, veterinarian, or keenly interested in animal breeding, this episode is your gateway to understanding the future of animal health and productivity.


Woolliams 2012. Influence of genetics and inbreeding on disease.
Download the pdf: http://www.instituteofcaninebiology.org/uploads/1/9/6/9/19691109/woolliams_2012_influence_of_genetics_and_inbreeding_on_disease.pdf

10 Key things to know about the coefficient of inbreeding

What is the coefficient of inbreeding and why should breeders understand what it means?

This podcast episode discusses ten key things you should know about COI, including why it is probably the most useful statistic for breeders to know about their dogs.

Discover the science behind COI and its role in quantifying genetic health risks, as well as the implications of inbreeding on overall fitness, including issues such as inbreeding depression and reduced genetic diversity. Learn about the significance of COI from both pedigrees and DNA and how you can use it to control the risk of genetic disorders in the dogs you breed.

The complex genetics of degenerative myelopathy (DM)

Join us for an enlightening journey into the intricate world of canine genetics, where we explore the complexities of degenerative myelopathy (DM), a crippling disease affecting mobility in dogs. In this episode, we delve into groundbreaking research that unveils the multifaceted nature of DM, tracing its similarities with human ALS and the pivotal role of the SOD1 mutation in both disorders.

Listen as we unravel the genetic web involving not just the notorious gene, but a team of genetic interactions influencing the disease. 

(https://www.instituteofcaninebiology.org/blog/the-lessons-from-sod1-and-degenerative-myelopathy)

 

Genetic History of Galapagos Dogs

There have been free-living dogs on the Galapagos Islands since at least the 1830s, despite efforts toi control the populations. This study found that these dogs have a complex history of mixing with purebred dogs. A genomic analysis of Galápagos Islands dogs reveals distinct ancestral backgrounds between historical and modern populations. Modern dogs show recent mixing with three clades of purebred dogs, the Mastiffs. Asian spitz breeds, and sporting dogs (retrievers, pointers, and spaniels). Surprisingly, despite the population control efforts, no genetic bottlenecks were detected, indicating ineffective management strategies. Analysis of historical dogs indicates a srong ancestral link to shepherd breeds, especially the German Shepherd. The study highlights the need for more effective conservation strategies for protection of the unique genetic plant and animal diversity on the islands.



Download pdf: 
https://www.sciencedirect.com/science/article/pii/S0960982224015069/pdfft?md5=0c7d4aa284fe68783f5c7f45b065afc4&pid=1-s2.0-S0960982224015069-main.pdf

Limits to restoring genetic diversity by outcrossing (Windig & Doekes 2018)

Outcrossing should reduce inbreeding levels and associated negative effects in highly inbred populations. In this study, we investigated the effectiveness of different outcrossing schemes using computer simulations. The inbreeding rate estimated for a 25-year period of 2.1% per generation in a highly inbred dog breed reduced to 1.8% when a single litter was produced by an outcross without backcrosses. To reduce the inbreeding rate below 1%, more than eight of the 14 litters born yearly in the recipient breed had to be outcrossed. However, outcrossing in pedigree dogs is usually followed by backcrossing and generally involves one or a few litters. Backcrossing reduced the effect of outcrossing considerably. When two litters were produced by an outcross followed by one generation of backcross, the inbreeding rate was 2.0% per generation. Continuously outcrossing was more effective than a single or a few outcrosses. When each newborn litter during 25 years had a 5% chance of being produced by an outcross, the inbreeding rate reduced to -0.2%. To investigate the possibility that new alleles were introduced from the donor population into the recipient population, the fate of different type of alleles (varying from completely lethal to beneficial) before and after an outcross was investigated by first simulating 80 years of natural selection prior to the outcross and then different types of outcross. Because natural selection reduced the frequency of lethal alleles before outcrossing, the introduction of a lethal allele that was segregating in the donor breed but not in the recipient breed occurred rarely. Introduction of slightly detrimental alleles or neutral alleles occurred more frequently. In conclusion, outcrossing only had a limited short-term effect unless repeated continuously. Nevertheless, it may help to buy time in which the population structure can be changed so that the effective population size increases.
 
(Windig & Doekes 2018 Limits to genetic rescue by outcross in pedigee dogs. J Animal Breeding & Genetics 135:238-248)

 

 

Using cross beeding for breed improvement: meet the Borgis!

When tail docking was banned in the UK, breeders were not happy about having boxers with long tails. Boxer breeder and geneticist Bruce Cattanach decided to see if he could produce Boxers with naturally bobbed tails with some clever breeding. Cattanach crossed one of his dogs with a Corgi that carried the gene for a naturally bobbed tail, and bred the F1 corgi-boxer hybrids back to a boxer. The results of this breeding experiment were remarkable!

What is the Coefficient of Inbreeding?

The coefficient of inbreeding (COI) is a key tool used by breeders to quantify homozygosity and the risk of inherited disorders caused by recessive mutations. The inbreeding coefficient was derived in the 1920s by Sewell Wright, a statistician at the USDA. Breeders knew that inbreeding increased uniformity in offspring, but also caused genetic disorders and a loss of vigor (inbreeding depression). Consequently, they needed a way to predict the level of inbreeding in livestock. Wright's COI quantifies the degree of inbreeding, allowing breeders to balance these competing effects.

 

Why do dogs have more cancer than other mammals?

Large dogs have higher levels of cancer than small ones. This is predicted by "Peto's paradox", which argues that larger animals should have higher rates of cancer than small ones.

Suprisingly, however, larger mammals like elephants do not have higher rates of cancer than small mammals like rodents. The difference might be related to genes that suppress tumor growth. In fact, elephants have many copies of a tumor suppressor gene called TP53. Could the difference in cancer rates between dogs and other mammals be due to inadequate tumor suppression genes? 

The Popular Sire Syndrome in Dogs

Popular sires in dog breeding, while initially seen as beneficial for breed diversity, are now recognized as a major contributor to the spread of genetic diseases. The podcast explains that the high number of offspring from these popular sires increases the frequency of recessive mutations in the population, leading to a higher probability of producing dogs with inherited disorders in subsequent generations. This problem is not solved by DNA testing because we can only test for muations we know about, but there are many lurking in the gene pool that we don't know about. The resulting rise in breed-specific genetic diseases is detrimental to breed health and highlights the need for responsible breeding practices to mitigate the negative effects of popular sires. Restricting the number of offspring per sire is suggested as a potential solution, although enforcement challenges remain.

More resources - blog post: https://www.instituteofcaninebiology.org/the-pox-of-popular-sires.html