Selection against inherited disease is necessary for lasting and widespread improvement in many aspects of canine welfare. Successful genetic selection requires 1) the motivation to change a trait in the population; 2) data or information to differentiate between animals with respect to that trait; and 3) sufficient control of breeding animals to direct specific matings.
These factors are demonstrated clearly in livestock, where the traits in question are associated with food production (e.g., milk yield). For farmers, the motivation in changing (increasing) the milk yield in their herd is profit, since higher yields generate higher returns. They are easily able to differentiate animal performance through assiduous recording of yields (which are pretty much universal since payment is linked to quantity). Finally, they have control over the breeding of the entire herd (often hundreds of animals). These three factors have resulted in the widespread genetic improvement in the performance of livestock and contributed to dramatic improvements in yields over the last 60 years. Furthermore, as a result of the overarching financial motivation, the abundance of data and complete control of breeding, it has been possible to identify strategies that maximize genetic gain while minimizing the risk of future problems due to inbreeding.
When it comes to breeding pedigree dogs, the situation is less favourable to elicit widespread genetic change. First, consider the motivation - what are most breeders' principal objectives? They are manifold; some breed primarily for success in the show ring or at field trials, and some breed for working ability (working gun dogs, herding dogs, guide dogs, sniffer dogs), but I suspect most are hobby breeders and intend the puppies to go to pet homes. Thus, although health is likely a universal consideration among dog breeders, it is only one of a multitude of selection objectives. Differentiation between breeding animals on 'merit' by dog breeders is highly subjective and has often been achieved by eye, experience, or anecdote (reflecting the principal motivations). Finally, individual dog breeders have only very limited control over the breeding population - usually one or very few animals. Given that dog breeders are quite individualistic or self-reliant in terms of judgment of merit and scale of operation, the use of health information to elicit widespread improvement in health is often suboptimal. DNA tests are an example of information that has been enthusiastically employed by dog breeders, possibly because they offer a simple and definitive result (and one impossible to evaluate visually), and they are consistent with individualistic operation.
The landscape of dog breeding means that some of the more sophisticated tools available to livestock breeders to maximise genetic gain will not be directly transferable to dogs. Nevertheless, there are measures that can be taken in several areas that will assist in improving the efficacy of selection for health, by focusing on the motivation, the information, and the control. In this short talk, I will highlight a few being undertaken in the UK.
It is important to stress that in the majority of cases, health already is one of the primary objectives of breeders. No one I've met explicitly intends to breed a dog with disease. However, in some cases primary motivations may supersede the motivation to breed for health; for example, the trend for greater exaggeration of breed-defining characteristics may have (inadvertently) led to compromising the health of some breeds (e.g., brachycephalic airway disease in Bulldogs or Pugs and skin conditions in Bassett Hounds).
If health can be linked to the primary motivations of breeders, then it will become a de facto selection objective. The introduction of vet checks at Crufts, barring progression of 'Best of Breed' winners failing the checks to group finals, is a way of linking health to success in the show ring. Health does appear to be a concern of puppy buyers. Raising awareness of and providing information on health to the general public could help to elicit changes in demand.
I covered a bit about the more effective use of health information in my earlier lecture (using EBVs for hip score to elicit more accurate selection). We have also heard about the importance of monitoring inbreeding in populations, and we must consider appropriate breeding strategies when there are DNA tests for simple Mendelian recessive diseases, i.e., multi-objective selection often within limited gene pools. Mate Select currently provides information on inbreeding coefficients of litters from potential matings, and shortly will include EBVs for hip and elbow score, and a simple population analysis for most of the breeds registered by the Kennel Club. The Kennel Club has a role to play, as the repository of health data and pedigree in the UK, in providing more accurate information regarding health and risks for both individual dogs and entire breeds.
Compared to livestock breeders, dog breeders have control over the breeding of far fewer animals. Coupled with a more individualistic or self-reliant ethos to dog breeding, possibly due to differing objectives and maybe even competition, the sharing and use of data to direct matings to meet common objectives is less widespread than in livestock sectors. However, health is a common objective (or should be, and is a universal if not the principal objective), and health information is increasingly available, allowing breeders to be more discriminating in mate selection. Therefore, breeders will continue to benefit from a range of tools designed to allow them access to the most accurate information relating to health, and that will allow them to use it in their own way since 'herd-wise' solutions are not realistic. The Kennel Club's role in collating and presenting as much health information as possible is critical in coordinating the efforts of a multitude of breeders to meet a universal selection objective.