Breeding – What can actually be inherited?

This week, Horse and Hound published an article in the verterinary section called ‘Sound in body and mind?’. It was all about what characteristics could actually be inherited from breeding. Such as, can you really inherit personality traits, temprement and even movement style?

Sire Vs Dam

In horse breeding, ‘sire’ is the name given to the father, and ‘dam’, to the mother. But mare and foalwhich parent is more important when it comes to breeding better behaved horses? It’s still a matter of debate, but science is currently looking for an answer. While both sire and da, contribute equally to the genetic make up of the foal, ( half number of chromosomes from the sire, half from the dam) mares contribute during pregnancy and the suckling period in a way that stallions don’t. Nutrition of the developing foetus, as well as exposure to stresses during gestation, can substantially impact the physical and psychological make-up of a foal. Furthermore, the relationship of the newborn with the dam and her behaviour has a major influence on the foal’s temperament. For this reason, although the genetic contribution is the dam, some progeny tests that include a score for temperament attach a value for the dam’s temperament which is twice that of the stallion.

Crucial first three weeks of life: Our interaction with the mare and foal is also critical. Research has shown that gentle handling of the mare has a positive impact on the reactions of her foal to humans. It strongly influences how the relationship with us develops throughout a foal’s life. This effect is noticeable even when the foal is a few days old and can be a deciding factor in the behaviour of older foals. Foals appear to be very tolerant towards humans and novel objects up until around three weeks of age, after which they become increasingly wary. This is very important, as if a young foal has a good early experience, his temperament will be shaped in a positive way that persists later in life.

Temperament Explained

Temperament is a fundamental psychological attribute, often used to describe a person’s or animal’s nature. It is thought that temperament is shaped by indiviual genetic make-up and early life experiences. Temperament also becomes fixed with age, to the extent that most horses and humans have developed a ‘default setting’ upon reaching adulthood.

Behaviour is influenced and shaped by temperament, When looking to purchase horse rearinghorses, owners often talk a lot about the horse’s temperament. A nice temperament would mean a non-aggressive, playful and docile horse, whereas one with a nasty temperament, would be the complete opposite. As well as affecting train ability and performance, temperament is critical to the relationship between horse and rider and can influence risk of injury and accidents. However, through my experiences of owning sports horses, you will often find that their temperament in the stable (ground work) will vastly differ from their temperament during ridden work- usually for the worst.

Two other psychological factors are influenced by temperament- mood and emotional reactions. These are temporary and relatively short-lived responses to current or recent situations. Although these factors are less well understood in horses than temperament, interplay between the three is likely to have a notable impact upon performance.

In 2008, a Dutch study looking into co-operation between horses and their riders found that emotionally reactive horses – those scoring more highly on tests of flightiness and reaction to environmental stimuli, including a tape-recording of a chainsaw – showed more evasive behaviour when being ridden. This showed itself as head shaking, tail switching and shying, which impacted negatively on how they performed.

Evidence that temperament may have a genetic basis comes from our understanding pf evolution. It is through this process that distinct types of horse – differentiated by characteristics such as size, strength and speed – have emerged. Our ancestors may also have selected horses for specific behaviours, creating breeds with defined personality traits that we can recognise today. Our ancestors may also have selected horses for specific behaviours, creating breeds with defined personality traits that we can recognise today.

Support for the idea of evolution of a temperament comes from a 2008 study carried out at Bishop Burton and Moulton Colleges and Harper Adams University. By scoring 1223 horses for six distinct personality traits, researchers identified that certain breeds did appear to have specific temperaments.Thoroughbreds displayed high degrees of dominance, anxiety, excitability, sociability and inquisitiveness. Irish draught horses were more protective, only moderately anxious and less dominant and excitable. Researchers also found that breeds with linked ancestry had similar personalities, consistent with the belief that temperament is an inherited characteristic.

A complex trait

Research has also focused on quantifying the genetic basis of temperament examining its inheritance in groups of Andalusians, Haflingers, warmbloods and thoroughbreds. Estimates of heritability suggest genetics contribute as little as 2% and as much as 30% of a horse’s temperament.

Wide variation in these estimates is due to difficulties in measuring temperament, which is ultimately a matter of opinion, as well as differences in the assessment techniques used. Temperament is a complex trait and its heritability will also vary between groups of horses, depending upon their breeding and upbringing. While these estimates may seem low they are comparable with other measures of performance. Heritability estimates for racing times, for example, in standard bred trotters, Arabs and thoroughbreds vary between 28-40%.

A 2012 study of British Eventing data by the University of Edinburgh revealed that horse showjumpingheritability of performance in sport horses is around 7-9% for dressage, 9-16% for showjumping and as low as 1% for cross country. On this basis, it would appear that temperament is inherited to a similar extent to that of athletic performance. It should therefore play a part in the selection of horses for breeding and the performance-testing of breeding stock and youngsters. This is already the case in some countries, such as Sweden, where stallion performance tests include a temperament one.

Personality tests

How precise are personality tests? In the hope of developing a more accurate way of selecting breeding and young stock, work has been carried out to identify genes that shape temperament. Between 2005 and 2007, Japanese scientists looked at 10 genes that could play roles in determining personality. They studied their association with temperament within a group of thoroughbreds.

Only one gene – which is associated with the chemical dopamine – yielded a positive result, a variation of which was associated with greater curiosity and lower levels of vigilance, or alertness, during the tests. Interestingly, variations of this gene are also associated with novelty seeking behaviour in humans – a personality trait whereby individuals embrace and explore new situations or stimuli.

It could be that horses with that particular copy of gene are more suited to equestrian activities such as cross-country or dressage, where they’re required to confront and deal with challenges. We can undoubtedly breed horses with better temperaments. Given the influence and inheritance of temperament, however, there is clearly a place for the development of more accurate and repeatable personality tests. While science has shown that temperament is inherited and has a genetic basis, it has also highlighted the contribution of non-genetic factors.

We must remember that environmental factors – specifically, the way in which we keep and interact with horses – play a big part in shaping equine personalities.

Apologies for not publishing this article sooner, I could not gain access to my blog on Thursday evening and was too busy yesterday. New article next week!

 

2 thoughts on “Breeding – What can actually be inherited?

  1. This is really an excellent review . I have been googling for about 2 hours to understand where we currently stand in regard to heritability of temperament in horses. still cannot understand that we have excellent heritability studies in production animals and evidence that you. Can breed less reactive cattle in a very short time by selection, yet we do not seem to do it in horses! There is a very high heritability , over 60 percent, in horses that crib bite, surely an anxiety linked activity , yet this does not seem to link to breed reactivity data.

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