At the interface between man and animal, the horse has a place and an intermediate role. It is a large herbivorous mammal whose impact on the useful agricultural surface is far from negligible. Produced in rural areas, it will be used in peri-urban areas, as shown by the establishment of equestrian centers, training centers and racetracks. It will then end up in the slaughterhouse like any other livestock. In terms of its social function, the horse is the support of a myth of power. Last representative of the great animals to rub shoulders with the man of the cities, it educates him in a relationship with nature which cannot be deviated as easily as with the dogs. This ability of the horse to impose its few quintals of muscles is undoubtedly its current success. This reintegration of the powerful nature in the urban fabric constitutes the main originality of the species and guarantees its future.
This obligation not to evacuate the animal reality that it imposes, and with which it is necessary to compose, does not prevent and seems on the contrary to favor the incredible support of myths that it tends to constitute. In the races where the owners confront each other by interposed horses, the spectators try to appropriate a part of the power and the richness exposed by the means of the game. In hippophagy, it is the symbol of social power that is consumed at least as much as the 250 grams of chopped steak. Eating horses gives strength and health… In horse riding, it is the myth of the noble and valiant knight that is appropriated. In breeding competitions, it is the search for a cultural and social identity that is expressed. We see it thus, the horse is a producer of material goods (muscles, power, speed, special aptitudes) but, in an at least equivalent way, of immaterial goods (prestige and social capital, natural balance touching the physical as well as the psychic, satisfaction of identity).
The equine industry in France
Racehorses are undeniably the financial engine of the system through gambling and betting. They are also the unconscious reason for the marginalization of the equine sector in agriculture. The archetype of the racehorse is the Thoroughbred, but it is declined according to more socialized models such as the A.Q.P.S. (other than Thoroughbred) which runs in the provinces or over jumps and the French trotter accessible to everyone. The saddle horse breeds represented by the French-Saddle and the Anglo-Arabian are oriented towards sport riding, dominated in France by the discipline of show jumping (C.S.O.). The two other Olympic disciplines, dressage (C.D.) and eventing (C.C.E.) have far fewer followers. On the other hand, the regular development of hedonistic riding using ponies and horses other than sport horses is growing. This phenomenon leads to the development of new competition disciplines, of which endurance races are the best example.
Draft horses (8 breeds) are used for new leisure activities, heritage conservation, land management and meat production. The latter is however in strong regression because of the regular decrease of horse meat consumption. The genetic concern of this very diversified sector seems important at first sight. However, the answers that research can provide do not always confirm the preconceived ideas and habits initiated by the equestrian community at the beginning of the 19th century. In fact, what the industry is asking of geneticists is that they help it to produce:
- healthy animals;
- high performance animals;
- estimators of this quality allowing the objective characterization of the offer and thus allowing the development of the marketing of animals on markets that are sometimes very speculative.
Moreover, demand is often individual and not very cooperative. An overall strategy based on obtaining genetic progress for this or that population of horses can emanate from the national level (role of the stud farms), but more difficult from the regional level, due to the technical weakness of professional structures dominated by a considerable proportion of amateurism and intense competition between real professionals, which does not predispose to cooperation. This is a significant difference with other animal productions that can be a source of misunderstanding.
The horse and the work of geneticists
For their part, geneticists are involved in two areas: molecular genetics and quantitative genetics. The work on the horse is thus declined in these 2 directions, each of which has large-scale applications.
Molecular genetics is used for the moment to meet the needs of identification and parentage control. Quantitative genetics, on the other hand, is used more to meet quality evaluation needs (production of annual indices and B.L.U.P., Best Linear Unbiased Predictor) than to obtain genetic progress, which is only a by-product.
Due to lack of knowledge, the industry’s demand for molecular genetics cannot be formulated other than in terms of current identification practices (from the usual hemotype to DNA polymorphism, from blood sampling to hair sampling).
Nevertheless, everyone is convinced of the usefulness of progressing in the knowledge of the equine genome to identify genes of interest for breeding. Without expecting immediate practical results, it is desirable to consolidate a pole of technical expertise on the horse that is strong enough to be able to quickly make the species benefit from discoveries made elsewhere (in humans, mice, or other domestic species), where the research resources mobilized are much greater. To do this, it is necessary to establish genetic maps of low and then medium density, which will allow to move to the stage of comparative mapping, thus facilitating the transfer of knowledge between species and the genetic analysis of traits of interest for breeding, whether they are of factorial type (genetic diseases, coat color, blood groups) or of continuous type (Q.T.L., Quantitative Trait Loci).
Research in quantitative genetics has been conducted since 1973. Very quickly, the problem of horse selection revolved around two axes: selection based on performance criteria in competition, which have since been called direct criteria, and selection based on indirect criteria, i.e., criteria related to the objective.
In 1976, the first publication of show jumping indices (I.S.O.) was released and, the same year, the first estimates of stallions on progeny in this same discipline. France was thus the first country to have statistical evaluation tools for its sport horses. The I.S.O., thus gradually substituted for earnings to evaluate the performance of sport horses, was used more in the regulations until now, when it has finally imposed itself. From 1980 onwards, a similar approach was taken for the French Trotter. On the other hand, as early as 1975, the first results concerning gallop races were met with muted resistance from the circles concerned.
The advances made in this sector of selection indices are:
- In 1986, the first routine indexation in France according to the B.F.U.P. method in animal model, known in the public under the acronym B.S.O. (B.F.U.P. jumping) or B.T.R. (B.F.U.P. trotting). These same tools exist since 1994 for gallop races, but their diffusion is not desired. Other domestic species (cattle, goats, pigs) followed later.
- In 1990, the development of a methodology for processing classifications in races (see boxes 2 and 3). The application of this new technique does not, unfortunately, allow us to be free of gains. It requires heavy calculations and has the disadvantage, in terms of development, of making the measurement of performance too abstract.
In terms of indirect selection criteria, it was necessary to go beyond conformation and address biomechanical and physiological problems, and even behavioral ones, to better identify the determinism of performance. The progress made in this field is:
- The practical improvement of a photometric method for characterizing conformation.
- The development of a field device based on accelerometric measurements which allows the quantification of locomotor parameters, and which can be used for routine tests (Equimetrix). All these topics cannot be discussed here. We will therefore limit ourselves to commenting on the 3 steps necessary for the success of a genetic improvement plan:
- The first is the definition of a clear selection objective designating the traits to be improved, their measurement and their weighting in the overall objective.
- The data must then be analyzed to establish their degree of heritability (i.e., how well they are transmitted from parents to offspring) and the genetic values of the candidates for selection must be estimated. These genetic values are the expectation of their production, knowing the results already known on all their relatives.
- These estimates must be integrated into a general selection plan aiming at obtaining the maximum genetic progress (the greatest possible average difference between the generation of the parents and their descendants, in the best time compatible with the demography of the population).
Objectives and selection criteria
The definition of an objective is easy to define in the case of racing breeds: it is to succeed in a national or international program. However, subdivisions of the objective can be made according to the race distances and the age at which success is expected. For sport breeds, the problem is more complex. First, horses are used in a variety of disciplines and faced with this diversity, breeders and their organizations tend to opt for an average objective where they intuitively weight the following characteristics:
- conformation and gaits;
- jumping ability
- dressage ability;
- gallop class
which are themselves positively or negatively related.
They will be reluctant, for marketing reasons, to display a specific objective even if they are in fact forced by the competition to specialize. Breeding competitions based on expert examination of conformation and gaits aim at an overall assessment. They are often criticized for being highly subjective and for giving too much weight to aesthetic criteria over other, more useful, criteria. Moreover, aesthetics conveys an ancient equestrian culture that revolves around the Thoroughbred and unconsciously perpetuates the symbolic struggles of 19th century society where the Thoroughbred was assimilated to the nobility, the half-blood to the bourgeoisie and the utility horse to the third state. Attempts were nevertheless made, especially in Northern Europe, to make these criteria more objective and to link them more directly to certain aptitudes. The aim was to evaluate more precisely the aptitudes of the animals. The competition loses in social symbolism but gains in technicality. This is what led to the development of different tests. But the increase in complexity of the devaluation system also creates recent problems. Horses can be at quite various levels of readiness, making it difficult to compare them. Therefore, the idea of extending the duration of the test to homogenize the level of preparation of the horses was gradually put forward in Germany and resulted in the so-called “100-day test”.
In addition, when the civil status and identification of horses become more reliable, the computerized management of the results of sporting competitions makes it possible to inform the breeding of the success of horses in their usual conditions of use. The use of this information is therefore becoming more important in the selection process. This is what prevails in France.
The genetic evaluation of the horse
Genetic evaluation by selection indices from collected measurements is not fundamentally different in horses from what it is in other species. There are two dimensions:
- The first, historical, relates the evolution of techniques, i.e., the passage from raw averages per sire to estimates by regression, then by generalization, to the fitting of mixed models (some effects of the model called fixed being estimated without a priori information, others called random effects being considered as belonging a priori to a population of known distribution). This is what gave birth to the B.L.U.P., first in a father model, then in an animal model.
- The second dimension is that of selection objectives which, if they are simple, such as success in tests, lead to an evaluation on a single trait and, if they are complex, force a multi-characteristic evaluation for which, unfortunately, we must admit that we do not always have the means that it supposes.
In this field, France, which has been publishing estimates of the genetic values of its breeding stock for show jumping since 1976, appears to be the leading country. Indeed, it has integrated these estimates in the breeding regulations and ensures their distribution by powerful telematic means (Minitel – 3615 HARASIRE).
This indexing technique, the B.L.U.P. in animal model, tends to become a standard for the genetic evaluation of horses in many countries. It has many advantages: evaluation of individuals without performance, considering selection and reasoned crosses and optimal corrections for the effects of age, year, and sex. The maternal effect is also considered. Furthermore, the use of all parentage relationships increases the amount of information available through the pedigree and allows for more accurate estimates, especially of young animals without their own performance. This optimizes the use of the available information. Only its implementation in the Thoroughbred field comes up against certain speculative interests that prohibit its development.
Optimization of selection plans
We know the optimal selection policies when animals of different ages are rivals. The best animals should be selected from all age groups and therefore the best B.L.U.P. should be retained, regardless of their age and accuracy. However, selection plans in horses should not be limited to calculating genetic values with an animal model.
Genetic progress is proportional to the intensity of selection, which determines the superiority of the selected animals, as well as to the accuracy of their genetic value estimates. It is also inversely proportional to the generation interval within a year. Genetic improvement programs must therefore aim to increase the average precision of the estimates in the minimum time possible. Thus, the possibilities of a significant annual genetic progress are limited by the length of the generation interval, which is on average between 10 and 12 years due to an often late start of reproduction (3-4 years and more), but especially due to a very long reproductive life span (>10 years). Furthermore, the number of offspring per parent limits the applicable selection rates which, under current conditions, can however be set at a minimum of 5% in males and 50% in females. When all the animals are controlled, as is the case with racehorses, this can lead to important selection intensities which partly compensate for the handicap of the generation interval.
All the studies conducted on this subject show that, for selection to be effective, it must first implement performance control. The usefulness of progeny control only becomes apparent when it can be carried out quickly. This usually implies the use of artificial insemination, which is not always easy to achieve. Therefore, performance control is the most key factor in horse selection.
Perspective of genetics in horses
Since the 1970s, studies on horse breeding have led to many developments and are often able to provide effective support to production. However, the strong sociological implication of this breeding, its cultural resonance, its speculative economy, which proceeds from the so-called leisure society, mean that the models established for other domestic species must be deeply transposed to be applied to horses. The modernization of the selection structures, which are still viscerally attached to tradition, depends to a large extent on the discovery of these angles of approach. Let’s hope that this attachment will no longer be a factor of immobility and blockage, but on the contrary, by relying on the ferment represented by this cultural heritage, it will allow original modern developments that can serve as a model for all animal productions. At the dawn of the 21st century, the interface between man and animal seems to be taking shape in a new way.
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