EFTBA Veterinary Newsletter 22

January 2017

Traditional Conventional . “Is performance selection, breeding the great historical contribu- methodsversus tion of Thoroughbred breed- sympathetic ing, still effective?” – asked - the geneticist Langlois (1996) training A review . He said ‘yes’, but considered the concepts currently in use as ‘very outdated’ Eclipse by Marske out of Spilletta by Regulus . Traditional methods are limi- “King of Sires” (Lowe 1913) ted and discussions of performance genetics are theore- Welcome to EFTBA’s veterinary newsletter tical due to our inability to Dear EFTBA Members, headed by Dr Des Leadon, as we are precisely identify the various Dear European Breeders, following their scientific lead knowing trait components and their the depth of their expertise. interactions Genomics… and genomics again. Even if this debate takes an important Fr om an outside point of view, one part of our time, the EFTBA was active- “Many thanks to Mrs. could feel like this topic is taking an ly represented at the recent ITBF mee- enormous part in the EFTBA activi- ting in South Africa. Congratulations to Eva-Maria Bucher- ties. And this should be right. In our Honorary Chairman who was no- Haefner, Moyglare fact, it is now and in the coming minated at the head of the new ITBF months that we will have to ask executive committee. ourselves the right questions about Stud Farm, for her There may be a Brexit in other part of genomics. The technics are moving the politics but there is a perfect har- valued sponsorship at speed light and, as the defen- mony at the European Horse level. of this newsletter.” sors of the European breeders, we don’t want to be at the back of With kind regards the pack. Once again, let me th ank Hanspeter Meier and all the Hubert Honoré Genomics Advisory committee Hubert Honoré Chairman, EFTBA Editorial

In our deliberations at meetings in deavors and monitoring their deve- the recent past, contributions to lopment is most important for us. We genetics and genomics always pla- already delved into this subject in

yed an important role and - most two of our first newsletters (5 & 6) - probably - will be of an even big- but this was in 2011, and in modern ger meaning for the future. This for genomics, five/six years already are the very simple reason that breed- a pretty long time. alt ing of animals addresses the evalu- Outstanding, first With this issue, just let us listen to the ation of the genetic value of live- XYopinion s of some un prejudiced ex- stock . Its scientific theory incorpo- perts about our traditional methods rates population genetics, quan- in the course of earlier times. titative genetics, statistics, and in Dr Hanspeter MeierIntroduction ourIntroduction days now also molecular genomics. These subjects are nothing EFTBA veterinary advisor & Newsletter else than the essence of our en- editor 1

Introduction ven this cost decrease have also facilitated the production of whole-genome sequences for several In the opinion of André Eggen (2014), genomics animal species – among them the horse. created nothing short of a paradigm shift in animal An impressive event for demonstrating the develop- breeding. Or in other words, he speaks of a new ment of modern horse breeding in comparison to era, the “genomics era” in animal breeding, thanks other fields in animals breeding occurred in 1990. to the rapid development of this new technology At the 4th World Congress on Genetics applied to over the past two decades. Livestock Production in Edinburgh, horse breeding However, this development didn’t start in the world was included as a special topic for the first time. of horse breeding. The most important reason for This was regarded as recognition of the importance this research in animal breeding was nothing else of the horse as a valuable asset to human welfare than the increase in growth of the global popula- in the form of leisure and sporting activities in motion. On the basis of current projections, the world dern society. But it also showed the appreciation of population will reach 9 billion people by 2030. the Congress organizers for the standard of recent Meeting the growing food need, using fewer re- scientific research published in the field of horse sources, therefore is one of the greatest challenges breeding. The title of the session was “Breeding for that agriculture is facing now. Recent estimations performance traits in horses” (Arnason, 1990). by the Food and Agriculture Organization of the United Nations (FAO, 2006) indicate that to meet Traditional and new breeding methods the increasing demand, food production must Nobody else knows better than we that breeders double in the next 50 years. It is therefore critical to have very effectively manipulated the genomes of apply technical and scientific advancements syste- livestock species for centuries. They made use of matically in feeding, nutrition, genetics, reproduc- the fact that natural variations exist within a spe- tion, animal health control, and general improve- cies, within a breed, and within a population. Tradi- ment of animal husbandry to fill the coming pro- tional breeding has been done in the absence of ductivity gaps. The largest gains will come from in- molecular knowledge of the genes acting on a novations that accelerate agriculture productivity quantitative trait locus. Breeders have enhanced while reducing costs and limiting environmental im- production traits in their herds by selecting superior pacts (Capper, 2011; Eggen, 2014). individuals as progenitors for the next generations. So far, these traditional breeding methods have Big Expectations of Genomics been considered good enough, but everyone also The rapid development of genomics over the past knows that these traditional methods are limited. two decades has opened new paths to address The main reasons for this fact are that ‘easy-to- the scientific basis of livestock biology and bree- measure production traits’ have hit an asymptote, ding. Nowadays we have direct access to the full and that ‘more difficult-to-measure traits’ cannot DNA sequence of the horse and therefore a new effectively be selected by using traditional me- and more objective view of the genetic value of thods. Difficulties exist also for traits with a low heri- animals. This fact promises to enable a much more tability or for parameters which cannot be quickly, objective prediction in breeding animals which is inexpensively and correctly measured in a large not limited to a few production traits, but e.g. also number of animals. Such traits are e.g. longevity, for traits in relation to the soundness of animals. disease resistance and fertility – often critically im- One of the triggering factors for the development portant subjects. Geneticists of our days therefore of the genomic era was the implementation of are of the opinion that selection for these traits must most efficient new genomic tools – a development be achieved through genomic means and it is con- which also led to the amazing fact that the price to sidered that a major proportion – if not all – of the sequence a single nucleotide of DNA has fallen 100 breeding animals will be genotyped in the future million fold since 1990 (Eggen, 2014). In todays (Eggen, 2014; Ibanez-Escriche & Simianer, 2016). cattle industry for instance, this allows projects to genotype more than a million animals (e.g. food ef- The action for such plans in animal breeding there- ficiency and methane emission in dairy-cattle). fore are, to improve and enhance the traditional The rate of information coming from current-gene- breeding methods with genomic selection. The esti- ration DNA sequencers is increasing exponentially, mation of breeding values (EBV) will genomically be and faster than other comparable high-growth sce- enhanced (GEBV). narios. Technological breakthroughs that have dri-

What does that mean for us, now? – I guess we best In regard to more specific information on breeding might have a look at the traditional breeding theo- itself, the “Order how to breed Horses” by Hodson ries in the TB-industry by means of a review of litera- and coworkers (1717) finds great interest, as he al- ture on this subject, first. ready mentioned one of our breeding goals – the soundness. Referring to “The Choice of your Stallion and Stud Mares” he wrote: “First and principally you Some historic testimonies of Thoroughbred- must foresee, that your Stallion and Stud Mares be breeding both of good and lively nature, and not subject to any natural Diseases. For as heavy (broken wind) In the search for hints to the beginning of breeding Horses and Mares will breed Colts of roilish and Thoroughbreds, we have to consult the English lite- heavy nature; so if they be infected with any na- rature, of course. And luckily for us, at these times tural Disease, their Colts for the most part shall be Shakespeare (1564-1616) gave us an idea on what troubled with the same Disease.” an ‘ideal horse’ should look like: And finally, approaching the subject of genetics, The ideal Horse the dissertation of William Osmer (1756) must find

Round-hoofed, short-jointed, fetlocks shag and long, great interest (A Dissertation on Horses: Wherein it is Broad breast, full eye, small head, and nostril wide, demonstrated, by Matters of Fact, as well as from High crest, short ears, straight legs and passing strong, the Principles of Philosophy. That Innate Qualities do Thin mane, thick tail, broad buttock, tender hide. not exist, and that excellence of this Animal is alto- Look what a horse should have he did not lack, gether mechanical and not in the Blood). - But only Save a proud rider on so proud a back. two examples are mentioned here:

(Shakespeare W., Venus and Adonis) - “Let us next inquire what information we can gather from the science of Anatomy, concerning Doesn’t this poem let us wonder whether Shake- the laws of motion: it teaches us, that the force and speare already had the idea of the method of power of a muscle consists in the number of fibres ‘Linear Profiling’ in our days? of which it is composed; and that the velocity and motion of a muscle consists in the length and extent McGrath (2016) tells us, that at about the same of its fibres.” time (1597), John Sanderson, the deputy ambassa- Doesn’t the last sentence remind us of the Myosta- dor to Constantinople, reported to Englishmen his tin-gene ? wonder over the ’Babilonian’ grey he rode to Aleppo. Despite the horse’s lack of substance, - Osmer also cites Virgil (lib III, 49-51): “Both those Sanderson reckoned his mount ‘the best … that who rear horses aiming the victory of Olympic palm, ever I shalbe master of’. The horse was not only and those who breed strong cattle for plough- indefatigable, he showed uncommon intelligence ing, should mainly choose the dams' conforma- and affection. ‘He would walke by me, licking my tion.”(Transl. Gaddini). hand; stand still when I backed him; and kneele at This citation, which puts great emphasis on the my pleasure.’ On reaching Aleppo, Sanderson pre- dam-line, certainly finds our approval. But funnily, sented the horse to a Levant Company colleague Osmer also dared to make comparisons to “all the who rode him to win a race against ‘the most well-made women in the kingdom” and a marginal famous beast in Alepo, cauled Berthrams mare’. note of a reader says that “the author appears to By 1684, Charles II and his entire court marvelled at know much more of what belongs to the Human three horses in St. Jame’s Park, captured at the than to the Brute Species” (Osmer 1756). siege of Vienna. They also were captivated as “They trotted like does, as if they did not feel the ground” and the finest of the three was “so delica- te a creature … such an head, eye, eares, neck, There is nothing in science that has not breast, belly, buttock, gaskins, leggs, pasterns & been before in experience feete in all reguards beautifull & proportion’d to (Leonardo da Vinci) admiration, spirituous & prowd, making halt, turning with that sweiftnesse & in so small a compasse as was incomparable, with all this so gentle & trac- table” (McGrath, 2016). 3

Traditional Thoroughbred breeding theories As the methods as above (table 1) almost exclusi- in the view of some geneticists vely are the work of insiders of the Thoroughbred industry, the following reviews have been written by professional geneticists and hopefully are objective Already more than 100 years ago, breeding theo- statements: ries had been developed, e.g. “Die Stamm-Mütter des Englischen Vollblutpferdes” by Hermann Goos - Tolley et al. (1985, USA): A Review of the Inheritan- ce of Racing Performance in Horses in 1885 and “Breeding Racehorses by the Figure System” by Bruce Lowe (1895). - James (1990, AUS): Selection Limits in Thorough- Thereafter, many more studies had been done and bred Horses most of them are well documented in several books - Langlois (1996, F): A consideration of the genetic on Thoroughbred breeding (table 1). Therefore, we aspects of some current practices in Thorough- don’t want to go into details of them here and bred horse breeding rather prefer to concentrate on reviews of geneticists, the experts in this field. Genetics and geno- - Bowling (2009, USA): Horse Genetics (Chapters mics are so demanding subjects that mastering ‘Genetics of performance traits’ & ‘Pedigrees and them only is possible in cooperation with these col- breeding schemes’) leagues. Moreover, their articles often are published in pretty specialised magazines and therefore out Tolley et al. (1985) of reach for us and not to be found easily. In regard to genetic aspects of our endeavours, the Some Traditional breeding methods inheritance of performance certainly finds our special interest. Therefore, the review of traditional methods of this subject is cited here. It was published Methods Examples more than 30 years ago, by Tolley et al. (from the Animal Science Department of the Virginia Poly- Statistics Earnings technic and State University, USA) and has the title Wins and Placings A review of the Inheritance of Racing Performance Winning distances (e.g. Average Win- in Horses. In this study, the authors reviewed the ning Distances AWD) methods of assessment of racing performance both Black Type figures in Thoroughbred and Trotter populations in a big Racing Times number of countries. Indices Timeform and Handicap Average Earnings Index (AEI), Annual They found that most studies had used some mea- Progeny Earnings Index (APEX) sure of racing time, money won or placing as crite- Hereditary Grid (Erbgitter) rion of evaluation. This formed their opinion that Comparative Index (CI, measuring the substantial evidence points to the existence of ad- quality of the mares to which the stal- ditive genetic variance for racing traits. lion was bred) Pedigree Origins Racing time appears to be moderately heritable in Analysis and Use both Thoroughbred and Trotter populations. In ge- Family Branches neral, most heritability estimates for money won are Inbreeding versus outcrossing moderate for Thoroughbreds and are somewhat Dosage Index (attempt to quantify the lower for Trotters. Heritability estimates from rankings amount of speed versus stamina) or placings for Thoroughbreds are somewhat higher Nicks than those for racing time, but are highly variable and often associated with large standard errors. Theories of Bruce Lowe, Hermann Goos, Sir Francis Galton, Jean Joseph Generally, heritability estimates in the investigations Vuillier, Franco Varola, etc. reflected poor data structure and also were sensiti- BLUP Best Linear Unbiased Prediction (Anne ve to sampling error. When sample sizes were rea- Ricard, 1988): Genetic analysis sonably large, heritability estimates were generally significant. It was to be concluded that mass selec- Table 1 Discretionary selection of traditional tion and testing of 2- and 3-year-old progeny may methods in Thoroughbred breeding (with no claim be employed to select superior sires based on ra- to completeness). So far, in comparative studies, cing performance. Timeform was the preferred parameter. 4

They did conclude that speed, money won and As causes of selection limits - a plateau in perfor- placing were integral parts of any method of eva- mance despite continued selection - he identified luation. But they also noted that these traits are in- several points: fluenced by genetic factors to a greater or lesser 1. Selection is not effective; degree depending upon the population. Therefore, 2. the environment is deteriorating; a recommended method of selection within one 3. natural selection opposes artificial selection; subpopulation may not be relevant to another such 4. additive genetic variance is exhausted. population. They also mentioned the limitation of genetic progress due to the long generation inter- Beside this, he also mentioned the concept of a val of racehorses. “physiological limit” but didn’t delve deeper into this subject. However, in the opinion of the editor, As favourable did they mention that racing perfor- this issue certainly also has to be looked at closely mance may be evaluated in both males and fema- (what will be done in a further newsletter). les, and that repeated observations can be obtain- ned on the same animal. These factors, coupled In regard to genetic trends and variations, James with the reasonable heritability of some measures of also referred to the work of Gaffney and Cunning- racing performance, suggest that mass selection ham (1988) who had tried to estimate a genetic based on performance tests would be the selection trend in Timeform ratings (using a simple sire BLUP procedure of choice. Information on racing perfor- analysis). They found the figure 0.94 units per year - mance of 2- and 3-year-old progeny could also be but, this result was in contrast with the phenotypic used, as it became available. This would increase trend of -0.32 units per year! This asked for an expla- the accuracy of sire selection, but progeny testing nation, and they attributed these findings to the in- that would unreasonably increase the generation clusion of a greater number of lowly rated horses in interval should be avoided. later years. This explanation indicated that horses used to supply data for analysis had been selected, James (1990) violating the requirement for validity of BLUP analyses (that all information used for making selection James (1990, Department of Wool and Animal decisions should be used in the analysis). This phe- Science at the University of New South Wales, AUS) nomenon is something which we also have to be investigated Selection Limits in Thoroughbred Hor- aware of in the case of older sires. If more poor ses. He first referred to winning times which, in performers are included over time, the apparent classic races of the last century, only had improved breeding values of older stallions would decline – little, if at all. He considered this fact as noteworthy, giving the wrong impression of genetic improve- because of the continued selection for racing suc- ment in the population. James (1990) warned that cess and apparently moderate to high heritability the analysis of such data should be treated with of performance. great caution. In his opinion, an agreement bet- He reasoned that actual heritability is almost cer- ween estimated trends and predicted responses tainly lower than appears, and that it is not certain might be fortuitous. He also did point out that esti- that performance and time are closely correlated. mates often are liable to upward bias through both In his opinion, a positive estimate of genetic trend in assortative mating and correlation between geno- performance may not be justified. It is conceivable type and environment. Heritabilities can be too that limited effective population size and intense high and the genetic process may be over-estima- selection have led to a plateau in performance, ted (rien est simple – et tout se complique). and that the appearance of heritability of perfor- With all these results, James was left without firm mance is illusory. conclusions. According to him, the phenotypic sta- James argued, whether it is possible that a selection bility may or may not reflect a genetic stability, limit has been reached, since there are clear ex- since the only real attempt to estimate genetic amples of such limits in laboratory populations, trend is subject to very strong reservations. More- though these may sometimes be surpassed by the over, the apparent existence of additive genetic provision of new variation through spontaneous or variance is also of doubtful validity. induced mutation or through crossing. He means that no matter which way one tries to re- If no genetic improvement is being made, one must solve the puzzle, one is led to the conclusion that ask why heritabilities and genetic trends for perfor- something needs to be done, either to improve the mance have positive estimates. horses or to improve those who deal with them -

unless one accepts that since horse racing is a fect ideal. – This meant seeking out stallions in matter of competition the only thing that matters is distant lands or regions! that differences should exist, no matter what their The concept of selection was only introduced later nature may be (James, 1990). (Darwinism) and the creation of the English Tho- Finally, the Australian reminded the readers of two roughbred reinforced these ideas, also imposing things: First that racing success isn’t a single trait, the idea of selecting for performance rather than and the rating can be viewed as an index of seve- for appearance. The Stud Books, by certifying line- ral traits. And second, although no further improve- age, made it possible to link performance not only ment might be made, selection is successful in that to the horse itself but also to its relatives. This open- better parents produce on average better proge- ed the way to genealogical selection and progeny ny, and if selection is suspended the average per- testing (Langlois, 1996). formance of the population will deteriorate (James, Until the dawn of the twentieth century, the horse - 1990). with which men identified very closely - was the sole focus for experimental testing of heredity theories. Langlois (1996) However, these theories developed in line with the sociological support they received. Langlois (1996) from the Centre de Recherche INRA Historically, the principal notions introduced by Tho- de Jouy-en-Josas (FR) reviewed and considered roughbred breeding were: The Genetic Aspects of some Current Practices in - selection on performance within a pure breed; Thoroughbred Horse Breeding. He analysed histori- - the introduction of precise management of identi- cal and sociological aspects and in respect to “the ty and lineage through the Stud Book; genetic problems involved in Thoroughbred bree- - reflection on the respective roles of mare and stal- ding”, he asked the questions: lion; - Is performance selection, the great historical con- - generalized use of planned mating.

tribution of Thoroughbred breeding, still effective? In our days now, Langlois (1996) wonders whether - Is breed purity a myth or a technically effective these ideas and customs of Thoroughbred breeding reality? still are justified? What has the scientific community - What about inbreeding? to say about these questions today? - What are the respective influences of the mare and stallion? In his review “Viewpoint of the Scientific Commun- Thereafter, he examined the answers put forth by ity” Langlois (1996) analyses: “Is performance selec- the scientific community. Finally, consideration was tion, historically the great innovation of Thorough- given to future prospects and to the progress requi- bred breeding, still effective?” red for genetic management “in an industry where Here he also refers to the controversy between the concepts currently in use are very outdated”. Gaffney & Cunningham and William Hill in the April According to Langlois (1996), horse breeding has its issue of Nature (1988), the contradiction between historical and sociological dimension, in which the selection and the failure to translate it into faster emergence of the English Thoroughbred was a ma- performance as already discussed by James (1990) jor innovation, an event of prime importance for (and others). the development of the art and which was and He reminds us that genetic variability does not simp- continues to be a frequent focus of controversy. In ly result from the variability of the genes at each lo- his opinion, it therefore seems important to situate cus, but also from covariance among the effects of the achievements of Thoroughbred breeding histo- these genes. Moreover, Langlois (1996) mentions rically and to conclude with a consideration of that correlation between genetic and environmen- future prospects. tal effects can be a further source of over-estima- In regard to history he mentioned creationist dog- tion. mas of the 18th century and the progress thanks to He is of the opinion that the great importance of Darwinian thinking. In this context is most interesting the trainer effect is a reflection of this phenomenon to hear that the creationists Buffon and Bourgelat (Schulze-Schleppinghoff et al., 1985, 1987; Preisinger wanted to return to the ideal type of the creation. et al., 1989, 1990) (table 2). The offspring of top- The latter therefore recommended choosing a stal- grade breeding stock usually is predestined for a lion of the opposite type of the dam to compen- top-grade training establishment, improving their sate for the divergence of her traits from the per- chances of a brilliant racing career (Langlois, 1996).

Langlois concluded that in the state of research petitors and can see no point in cooperating for findings 20 years ago, it appears that racing perfor- genetic improvement (Langlois, 1996). mance in Thoroughbred horses is moderately heritable, and is best expressed as the number of races In regard to prospects, he considers the clear esta- won and ranks, independently of performance blishment of breeding values as difficult. This leads against the clock. It is not surprising that, despite to a kind of poker game on a large scale, in which selection, time performance is improving very little, the operators have no interest in openness or because no one is trying to improve it. However, this visibility. in no way implies that there is no real progress in It seems important, first of all, to considerably impro- Thoroughbred populations. ve the performance criteria used. Many statistical To the question asked in the introduction, Langlois publications on gross prize money seem altogether (1996) would answer: Yes, performance breeding is outdated and ought to be improved. The new still effective in the Thoroughbred, but it no longer techniques could themselves be improved by using effects speed as such. It probably now affects only ranks rather than prize money. the physiological and psychological traits connec- A second stage would be to establish precisely the ted with racing effort. Racing effort can be defined degree of heritability of racing performance in the as an abrupt shift from a submaximum speed to a Thoroughbred. There is much debate on this subject maximum speed, for a brief moment. This sudden in scientific circles, and the facts must be definitive- acceleration is prompted by challenges from other ly established. horses. It is commanded by the horse’s psychologi- Why should one pay more for this or that pedigree cal make-up and involves the mobilization of anae- or high-performing sire if performance is not herit- robic muscular metabolism. The number of such able? It would be nonsense. However, this problem efforts a horse can make during a race is limited is already largely solved. According to Preisinger et and depends on its resistance and fighting spirit al. (1990) and Schulze-Schleppinghoff et al. (1987), (Langlois, 1996). it would seem that most of the hard-to-verify envi- From the examination of all these questions, Lang- ronmental effects are trainer effects. The German lois (1996) thinks that the genetic management of analyses take into account the trainer effect, and this considerably reduces heritability (table 2). Thoroughbred populations could be greatly improved by using methods that research has already vir- The values which Langlois and Chico (1989) have tually perfected. In his opinion, horse breeding is a obtained for the same variable, without correction very old-fashioned industry, convinced of the firm for the trainer effect, are around 0.25 and pro- grounding of its archaic methods, and does not bably constitute an upper limit. Fine-tuning this ap- seem ready to adopt these proposals. proach is all that is required for drawing a definite The reason is that there are very few technical org- conclusion on this issue (Langlois, 1996). anizations responsible for coordinating horse breeding. Breeders regard their fellow breeders as com-

Trainer effect in heritability values (*Last publication on the data 1987 resp. 1990)

Schulze-Schleppinghoff et al. (1985) Preisinger et al. (1989) Authors *Schulze-Schleppinghoff et al. (1987) *Preisinger et al. (1990)

Criteria Handicap Annual Earning Rank 2 years old 3 years old 4 years old earning per race per race Heritability 0.22 0.35 0.38 - 0.26 0.32 without the *0.22 *0.48 *0.52 *0.51 *0.13 *0.14 trainer effect Heritability with 0.23 0.09 0.14 - 0.17 0.19 the trainer *0.20 *0.20 *0.19 *0.11 *0.07 *0.07 effect

Table 2 Comparison of heritability values obtained in Germany, taking into account the trainer effect or not.

Bowling (2009) theory, the breeder must set environmental components to be maximally advantageous and: In the preface of her book “Horse Genetics”, Ann . have breeding stock with genetic variation for the Bowling from California mentions that genetics text- trait, books seldom mention horses and that breeders . know the accurate predictors of performance ex- cannot relate fruit flies, corn an mice to their practi- cellence, cal work. She shows understanding for this circum- . minimize generation intervals and stance and admits “that genetics is a subject that . practice high selection intensity. can only be taken in small doses”. But she also Bowling (2009) describes the most important theore- notes that knowledge about horse genetics lags tical aspects comprehensively and we only can list well behind that for human or mouse or even for them here. But this list alone already shows, how other domestic animals. – Quite a difference to a very complex traditional genetics of performance statement in one of my favourite books as a young traits are: vet (Pferdezucht, Löwe und Meyer, 1974), where - Performance breeding plans the authors stated: “Occasionally, one surely didn’t - Genetic variation in performance traits (heritabili- unjustly state the thesis that the crown of animal ty) breeding is due to Thoroughbred breeding”. - Racing performance In addition, Bowling with her great experience also - Conformation shows empathy for us with the advice: “When you - Predictors of performance excellence reach your saturation point, stop for the moment to - Generation interval return at another time.” - Selection intensity In the chapter ‘Genetics of performance traits’, she - “Cunningham’s paradox” (Cunningham, 1975) reminds us that many horse breeds are distinguish- ed by a particular performance ability and that Averaged heritability estimates these hallmarks were established prior to an under- in racing performance (Hintz 1980) standing of genetics or modern breeding theories. She also puts emphasis on the unifying theme in Thoroughbreds Trotters Pacers Log of horse breeding that the purpose for which most 0.49 0.41 - modern horses are bred requires athletic ability and earnings the savvy to interpret and obey instructions from Earnings 0.09 0.20 - their human companions. The close relationship of Handicap 0.49 - - the horse to a human handler distinguishes breed- weight ing goals for horses apart from other livestock spe- Best handi- 0.33 - - cies. That special abilities are inherited, is intuitively cap weight clear, but none seems to be inherited as a simple Time 0.15 0.32 - genetic trait. Performance characteristics may be Best time 0.23 0.25 0.23 controlled by genes at several loci acting together in an additive fashion (quantitative trait loci). Table 3 Just one example of very illustrative tables Quantitative traits are measurable and influenced and diagrams in Bowlings’ Horse Genetics (2009) by the environment (e.g. nutrition, trainer, rider, weather) as well as by genes. A common estimate of heritability is called the Our comprehension of the inheritance of perfor- Heritability Index (HI), which ranges from 0 - 1. mance traits strongly depends upon our ability to . An HI index of 0 means that none of the identify and measure genetic and environmental variability of the trait among individuals in the effects as separate components. A discussion of study sample is the result of genetic factors; horse performance genetics is largely theoretical . an HI of 1 indicates that all of the variability of due to our present inability to precisely identify the the trait among individuals in the study sample various trait components and to predict the out- is the result of genetic factors. come of their complex interactions (Bowling, 2009). Classification of Heritabilities: According to Bowling (2009), the successful breeder High heritability: more than 0.45 is one who can identify and combine the available Mean heritability: 0.2 – 0.4 components of genetic and environmental excel- Low heritability: 0.01 – 0.15 lence. To benefit optimally from genetic selection 8

In the following chapter ’Pedigrees and breeding References schemes’ she describes and illustrates: Arnason T. (1990): Chairman’s Introduction: Breed- - The pedigree format ing For Performance Traits In Horses. Proc. 4th World . Standard diagram Congress on Genetics applied to Livestock Produc- . Relatedness and “percentage of blood” tion XVI Edinburgh 23-27 July 1990, 181-183 . Evaluation of pedigree influences - Inbreeding and linebreeding Bowling A.T. (2009): Horse Genetics CAB Internatio- . Toward homozygosity and closed studbooks nal, Wallingford OX UK & Cambridge MA USA

. Inbreeding in short versus long pedigrees Capper J.L. (2011): Replacing rose-tinted spectac- - Outcrossing les with a high-powered microscope: The historical - Assortative mating versus modern carbon footprint of animal agricul- . positive assortative mating (mating like to like) ture. Anim. Front 1(1):26-32 . negative assortative mating (mating together animals of unlike phenotypes) Cunningham E.P. (1975): Genetic studies in horse - Tail-male lineage populations. Proc. International Symposium on - Tail-female lineage, strain breeding and families Genetics and Horse-Breeding. Royal Dublin Society, - Questioning breeding myths in the light of genetics September, pp. 2-6 . Nicks . Basing a program on champions Eggen A. (2014): The development and application . The cult of the dominant sire of genomic selection as a new breeding paradigm. Illumina Inc., San Diego, CA 92121 / 22nd December

Finally, Bowling (2009) gives her opinion on ‘Using Gaffney B. & Cunningham E.P. (1988): Estimation of genetics to guide a breeding program’. She says genetic trend in racing performance of thorough- that if assays for genes important for program goals bred horses. Nature 332, (21 April), 722 - 724 are available, the probability of obtaining foals with doi:10.1038/332722a0 selected traits from specific breeding pairs can be predicted. But so far, this is applicable only to horse Goos H. (1885): Die Stamm-Mütter des Englischen coat colors, but conformation and performance Vollblutpferdes. Rademacher, Hamburg traits are not well enough defined for predictive Hill W.G. (1988): Why aren’t horses faster? Nature values to be assigned. So little is known about the 332, (21 April), 678 doi:10.1038/332678a0 genetics of desirable traits, it is premature to suggest that any general technique of structuring pedi- Hodson M. et al. (1717): Gentleman’s JOCKEY, and grees consistently produces either better or worse approved FARRIER Instructing in the Natures, Cau- stock. The important lessons to learn from genetics ses, and Cures of all DISEASES incident to HORSES, to use for horse breeding decisions may seem London, 79f nebulous to those looking for easy “how-to” information. Yet an appreciation of how genes are in- Ibanez-Escriche N. and Simianer H. (2016): Animal herited, the number of genes involved in the make- breeding in the genomics era. Animal Frontiers Vol. 6 No. 1, p. 4-5. doi:10.2527/af.2016-0001 up of a horse, their variability within a breed and then the inevitability of genetic trait reassortment Langlois B. (1996): A consideration of the genetic with every individual in every generation will pro- aspects of some current practices in Thoroughbred vide the critical foundation for sound breeding de- horse breeding. Ann Zootechn 45, 41-51 cisions. With the current interest in genetics and the new Löwe H. und Meyer H. (1974): Pferdezucht und technologies available for looking at genes at the Pferdefütterung, 4. Auflage. Verlag Eugen Ulmer, molecular level, information about inherited traits of Stuttgart, 192 horses is likely to increase significantly. Lowe B. (1913): Breeding Racehorses by the Figure In her opinion, the future looks very promising, fortu- System. Facsimile Edition, edited by William Allison, nately (Bowling, 2009). Libra Books Canberra 1977

In a study of heredity animals provide a more re- McGrath C. (2016): Mr. Darley’s Arabian. John liable field of research than man, for their matings Murray, London, p. 18 can be controlled and the results checked with less likelihood of deception (Federico Tesio, 1958) 9

Osmer W. (1756): A Dissertation on Horses: Wherein it is demonstrated, by Matters of Fact, as well as from the Principles of Philosophy. That Innate Qualities do not exist, and that excellence of this Animal is altogether mechanical and not in the Blood. Waller, London. pp. 14-15 and 24-25

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Preisinger, R., Wilkens J., Kalm E. (1990): Breeding Thoroughbred Breeders values and estimation of genetic trends in German Associations th Thoroughbred horses. Proc. 4 World Congress on 257 Avenue le Jour se genetics applied to livestock production, Lève Edinburgh, 23-27 July, vol. XVI, 217-220 92655 Boulogne CEDEX Ricard A. (1988): Advantages of BLUP Animal Model for Breeding Value Estimation in Horses. Livestock France Production Science 20(2):149-160, October DOI: 10.1016/0301-6226(88)90059-0 E-Mail: Schulze-Schleppinghoff W., Kalm E., Bormann P. [email protected] (1985): Analyse der Rennleistung bei Vollblut- pferden in der Bundesrepublik Deutschland. 36th Web Site: EAAP Annual Meeting (horse comm.) Kallithea, www.eftba.eu Greece

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January 2017 ● Issue 22 ● EFTBA