Genetic parameters of morphofunctional traits in Andalusian horse

Livestock Production Science 60 (1999) 295–303

Genetic parameters of morphofunctional traits in Andalusian horse A. Molina*, M. Valera, R. Dos Santos, A. Rodero ´ Department of Genetic Veterinary Faculty, University of Cordoba, Avda. Medina Azahara s /n, 14005 Cordoba , Spain

Abstract The aim of this study has been to estimate for the first time the genetic parameters of 18 morphofunctional traits in the Andalusian Horse. The data were obtained from the evaluations made on 1273 horses between the years 1991 to 1997. The heritabilities and genetic correlations of these traits were estimated using a BLUP Animal model with REML methodology. The heritabilities obtained for the body measurements were moderate to high (0.35 to 0.95). The estimates obtained for the scored regional conformation show a lower value (0.03–0.50). The heritability for the racial fidelity and overall forms were of 0.58, while the scoring for movements shows a value of 0.15, and 0.08 for temperament, which agrees with the fact that they are the most subjective and complex features being closely tied to the behaviour variables. Lastly, the heritability of the overall evaluation trait, which includes all the previous characters, shows an intermediate magnitude (0.25). The phenotypic and genetic correlations estimated were all positive. The genetic correlations range between 0.11 and 0.94 for zoometric measures and between 0.12 and 0.91 for the regional morphologic evaluations. The punctuation for racial fidelity and overall forms shows a genetic correlation of 0.55 with movement scorings and 0.74 with the overall evaluation of the animal.

´ ´ Resume ´ ´ ´ d’estimer pour la premiere ` fois les parametres ` ´ ´ ` morphofonctionL’objectif de cette etude a ete genetiques de 18 caracteres ´ ont ete ´ ´ obtenues a´ partir des evaluations ´ ´ ´ sur 1273 nels chez le cheval Andalou (Pure Race Espagnole). Les donnees realisees ´ 1991 a` 1997. Pour le calcul de ces parametres ` ´ ´ ` Animal chevaux entre les annees genetiques, on a utilise´ le BLUP modele ´ ´ ´ obtenues pour les mesures zoometriques ´ avec la methodologie REML. Les heritabilites sont de grandeur moyennement´ ´ ´ hautes, oscillant entre 0.35 et 0.96. Les estimations obtenues pour les evaluations morphologiques regionales presentent une ´ ´ ´ pour la fidelite ´ ´ raciale et la harmonie de formes est de 0.58. La valeur sensiblement inferieure (0.03–0.50). La heritabilite ´ ´ evaluation par mouvements presente une valeur de 0.15; ce qui concorde avec le fait que c’est le caractere` le plus subjectif, ´ ´ ´ du et le plus complexe etant donne´ qu’il est intemement uni aux variables du comportement. En dernier, la heritabilite ´ ´ ´ ´ ponctuation total, presente une grandeur intermediaire (0.25), en incluant tous les anterieurs. Toutes les correlations ´ ´ ´ ´ ont ete ´ ´ positives. Les correlations ´ ´ ´ genetiques et phenotypiques estimees genetiques oscillent entre 0.11 et 0.94 pour les ´ ´ ´ ´ ´ raciale et la harmonie measures zoometriques, entrer 0.12 et 0.91 pour les evaluations morphologiques regionales. La´ fidelite ´ ´ une correlation ´ de formes a presente de 0.55 avec la valoration au mouvemente et de 0.74 avec l’evaluation globale de l’animal.  1999 Elsevier Science B.V. All rights reserved.

*Corresponding author. Tel.: 1 34-957-218-707; fax: 1 34-957-218-666. E-mail address: [email protected] (A. Molina) 0301-6226 / 99 / $ – see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S0301-6226( 99 )00101-3

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Keywords: Andalusian horse; Conformation traits; Genetic parameters; Heritability

1. Introduction The Andalusian Horse is subjected to debate at the present time for the elaboration of an improvement program among the Breeder’s Associations, the MAPA (Ministry of Agriculture, Fish and Food), the Leadership of Horse Breeding (a Military Organisation responsible for the Stud-Book of the Andalusian Horse) and researchers at the Veterinary Faculty in Cordoba (Departments of Genetics, Physiology, Anatomy and Ethnology). In spite of being one of the oldest horse breeds in the modern world (contributing to the formation of diverse American, European and Australian horse breeds), at the present time, the objectives of selection in the breeding of the Andalusian Horse have not been clearly determined. This is a highly versatile breed in the horse world, having good qualities (‘beauty, boldness, intelligence, nobility, agility and resistance’) that make it a prized animal whether as a saddle horse, dressage, bull-fighting horse, work horse, light cart-horse and even a sports horse. This fact makes its features related to structure, functionality and temperament more economically important than in other breeds (Bruns et al., 1978; Koenen et al., 1995) and make it essential to clarify the objectives of selection (Schwark et al., 1988; Preisinger et al., 1991). To meet these objectives, it is necessary to know the genetic parameters (heritability and genetic correlations) of the characteristics which have been ‘selected’ at the present time in the Andalusian Horse. This fact will allow us in the near future to determine the evaluation strategy in response to selection of determined objectives.

2. Material and methods To carry out the present study, we used data from the evaluations of the Andalusian Horse Commission for the years 1991 to 1997. After the compilation of records, we eliminated the registers of animals evaluated at an age other than 4 years old. The later

analyses were made with the 1273 remaining animals. The traits analysed included seven zoometric body measures (height at withers, height at chest, body length, width of chest, heart girth circumference, knee perimeter and cannon bone circumference), seven scored regional conformations (evaluations of head and neck, shoulders, withers, back and loins, chest and thorax, croup and tail, and legs and stance of the legs), a scored evaluation of racial fidelity and overall features, an evaluation of movements, and a scoring temperament evaluation. The range of scores was from one to ten except the total score, which was from 10 to 100 points and are not scored on a linear scale. The punctuation for movements takes into account agility, height of the movement, extensions, harmony and pace of movements, reunion and turns on hindquarters. The punctuation for temperament takes into account the ease of response to command, basic dressage, and gentleness. The total score is obtained by adding the partial scores of each concept, multiplied by a weight coefficient, which varies with sex (Table 1). The statistical analysis of the different variables, was performed by S.A.S. (S.A.S., 1991) version 6.03 package. The genetic parameters (heritabilities and genetic correlations) of these traits were estimated by means of the VCE programs (Groeneveld, 1998) version 4,

Table 1 Weight coefficients of partial scores for obtaining the total score Partial scores

Sires

Mares

Head and neck Shoulders Withers Back and loins Chest and thorax Croup and tail Legs and stance legs Racial fidelity and overall forms Movements Temperament

1 0.5 0.5 1 1 1 1.5 1 1.5 1

1 0.5 0.5 1 1 2 1.5 1 1 0.5

A. Molina et al. / Livestock Production Science 60 (1999) 295 – 303

using a bivariate mixed animal model including sex, birth year and stud of animal as fixed effects and animal additive genetic effect and residual error as random effects. To complete the pedigree for the calculation of the inverse of the relationship matrix, the stud-book of the Andalusian Horse was used, and all the inscribed ancestors of the animals evaluated were added, giving a total figure of 5889 animals. The additive genetic variance and covariance of the traits were estimated according to the Restricted Maximum Likelihood procedure (REML) using a Quasi-Newton algorithm with exact derivatives to maximise the log likelihood. An approximate standard error (SE) of the genetic parameters was estimated from the inverse of the approximation of the Hessian matrix when convergence was reached (Groeneveld, 1996).

3. Results

3.1. Statistical description of the variables analyses

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Table 2 Descriptive statistics of the body measures and the scored morphological evaluations in 1273 Andalusian horses Means C.V.a

Min.b

Max.c

1.55 0.74 1.58 0.43 1.89 0.31 0.19

1.48 0.68 1.48 0.38 1.71 0.20 0.18

1.71 0.81 1.74 0.52 2.10 0.39 0.21

Scored regional morphological conformation ( points) Evaluations of head and neck 7.56 3.40 5.60 Evaluations of shoulders 7.79 2.84 6.66 Evaluations of withers 7.79 3.50 6.00 Evaluations of back and loins 7.34 3.50 5.00 Evaluations of chest and thorax 7.74 4.00 5.00 Evaluations of croup and tail 7.34 2.96 5.70 Evaluations of legs and stance legs 7.29 4.00 5.00

9.00 9.50 9.50 8.50 9.00 8.66 9.00

Other scored evaluations ( points) Racial fidelity and overall forms Evaluation of movements Evaluation of temperament Overall evaluation

9.00 9.00 8.60 85.30

Body measures (meters) Height at withers Height at chest Body length Width of chest Heart girth circumference Knee perimeter Cannon bone circumference

7.69 7.63 7.68 75.23

2.31 3.31 2.69 4.96 3.55 5.12 3.74

4.00 3.00 2.60 4.30

5.00 6.00 6.00 61.00

a

C.V. 5 coefficient of variation. Min. 5 minimum. c Max. 5 maximum. b

The results of the descriptive statistical study of the zoometric measurements referring to the quantitative variables, the seven regional morphological evaluations, the evaluation of the overall forms, movements, temperament and the global evaluation are shown in Table 2 (the measures are expressed in meters and variation coefficients in percentage). The variable that shows the greatest variation is the perimeter of the knee, whereas the height of the withers is the trait that shows the least coefficient of variation. The morphological evaluations of the chest-thorax, legs-stance and the overall forms are those that show a great coefficient of variation. On the other hand, the temperament evaluation shows less variation, a logical consequence of the balanced and ‘tempered’ character of the Andalusian Horse. At the same time, the evaluations of the back and the withers are those that received the greatest number of points, whereas the variables for the legs-stance were the most deficient in average punctuation, clearly showing the most serious problem of the Andalusian Horse at present.

3.2. Genetic parameters The principal goal of this work was to estimate the heritability and the genetic correlations of the 18 variables analysed (Tables 3, 4 and 5). For the zoometric body measurements analysed (Table 3) we observed that four (height of withers, body length, width of chest and knee perimeter) reached a h 2 higher than 50%. In fact, the knee perimeter had the highest h 2 (h 2 5 0.95) and the cannon bone circumference had the lowest h 2 (h 2 5 0.35). The genetic correlation ranged between 0.11 (width of chest-knee perimeter) and 0.94 (height at chest-perimeter of thorax) and those of the phenotypical correlations between 0.15 (knee perimeterheight of chest) and 0.60 (heart girth circumferenceheight at chest). For the morphological evaluations (Table 4) the

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Table 3 Estimates of heritability (diagonal), genetic correlations (below diagonal) and phenotypic correlations (above diagonal) and their standard errors (6) of seven zoometric measurements

Height at withers Height at chest Body length Width of chest Heart girth circ. Knee perimeter Cannon bone circ.

Height at withers

Height at chest

Body length

Width of chest

Heart girth circ.

Knee perimeter

Cannon bone circ.

0.5860.136

0.3660.057

0.5560.051

0.2560.059

0.3060.059

0.4760.055

0.4460.055

0.8060.083

0.4960.094

0.4760.054

0.1960.060

0.6060.049

0.1560.061

0.2960.059

0.7260.069

0.8260.100

0.7260.100

0.3460.058

0.4960.053

0.2960.059

0.3660.057

0.2260.172

0.2860.112

0.6360.102

0.5660.123

0.5060.053

0.3860.057

0.3760.057

0.6060.099

0.9460.037

0.7760.081

0.4960.102

0.4860.088

0.2460.060

0.3760.057

0.3360.132

0.2660.073

0.4460.072

0.1160.112

0.3260.106

0.9560.028

0.5760.051

0.4860.171

0.2760.160

0.2260.136

0.2260.171

0.3460.156

0.4060.138

0.3560.108

Table 4 Estimates of heritability (diagonal), genetic correlations (below diagonal) and phenotypic correlations (above diagonal) and their standard errors (6) of seven regional morphological evaluations

Head and neck Shoulders Withers Back and loins Chest and thorax Croup and tail Legs and stance

Head and neck

Shoulders

Withers

Back and loins

Chest and thorax

Croup and tail

Legs and stance

0.2360.169

0.3460.085

0.3560.085

0.2260.088

0.2260.088

0.2260.088

0.1660.089

0.7260.282 0.6060.246 n.c.

0.4760.180 0.1760.187 0.1660.626

0.5960.073 0.5060.152 0.7660.455

0.2360.088 0.3460.085 0.2760.159

0.5260.077 0.4760.080 0.2660.087

0.3460.085 0.3060.086 0.5460.076

0.3160.086 0.4160.082 0.2660.087

0.6960.292

n.c.

n.c.

n.c.

0.4060.142

0.3560.084

0.5060.078

n.c.

n.c.

n.c.

n.c.

n.c.

0.0360.065

0.2860.087

0.1260.881

n.c.

0.9160.265

n.c.

0.8360.299

n.c.

0.2960.137

n.c.: Convergence was not attained.

Table 5 Estimates of heritability (diagonal), genetic correlations (below diagonal) and phenotypic correlations (above diagonal) and their standard errors (6) of other scored evaluations and the total score

Overall forms Movement Temperament Total score

Overall forms

Movement

Temperament

Total score

0.5860.135 0.5560.453 n.c. 0.7460.191

0.3460.085 0.1560.155 n.c. n.c.

0.3260.087 0.2860.088 0.0860.044 n.c.

0.7760.058 0.5060.078 0.3760.085 0.2560.123

n.c.: Convergence was not attained.

A. Molina et al. / Livestock Production Science 60 (1999) 295 – 303

highest h 2 was reached in the score of the withers (0.50) and the lowest in the score of the head-neck (0.23). The genetic correlation ranged between 0.12 (score of legs stance-score of head neck) and 0.59 (score of withers-score of back). For the evaluation of the overall shapes the h 2 was of 0.58, the h 2 for the scoring of movement was 0.15, 0.08 for temperament and 0.25 for total score (Table 5). For this third group of variables we only got convergence in the correlations between the score for the overall forms and movement (0.55) and the score for the overall forms and total score (0.74). The phenotypic correlation ranged between 0.28 (score of temperament-score of movement) and 0.77 (total score-score of overall forms).

4. Discussion

4.1. Statistical description of the variables analysed The present investigation indicated that from a morphological and zoometric point of view, the Andalusian Horse may be regarded as an eumetric to sublongitudinal animal with a subcirtoide aloidism ´ 1953; Andrade, 1954; Castillo, 1979). (Castejon, Appreciable differences exist between results obtained by other authors for all the zoometric measurements analysed except in the case of the height of withers. In fact, the work by Pozo (1954) shows an animal with an inferior height to that found by the rest of the authors consulted and to that found in our study. On the other hand, if we compare them to the Carthusian strains animals (Valera and Molina, 1995), we find the averages obtained in this breed are higher, possibly due to the fact that this group of horses is considered one of the most prestigious and most relevant among Spanish horse ranches. The measurement of length found in our group of animals is greater than that detected by most other authors consulted, except that of Valera and Molina (1995) in a group of horses belonging to the Carthusian strain. This is possibly due to the high Carthusian influence (nearly 70%) at the present time in the rest of the population of the Andalusian Horse (Valera, 1997). The width of chest and heart girth circumference

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measurements in our animals are higher than those found in the bibliography (Molina, 1920; Pozo, 1954; Aparicio et al., 1986; Valera and Molina, 1995), whereas the knee and cannon bone circumference are lower than those found by other authors consulted (Molina, 1920; Pozo, 1954; Aparicio et al., 1986). The coefficients of variation obtained for both the body measures as well as for the different regional morphological evaluations and those of movement and temperament scores have shown that we have 17 extraordinarily fixed characteristics, since they present a very low variability ranging from 2.31% (withers height) to 5.12% (knee perimeter). These results coincide with those of Aparicio et al. (1986), where the average coefficient of variation was around 3% and with evaluations obtained by Valera and Molina (1995) with an average coefficient of variation of 2.98%. The analysis of the different zoometric measurements, in comparison with those found by the different authors, show that at the present day, Andalusian Horse tends to be more eumetric than sublongitudinal, with a great thoracic capacity along with a more open chest. It is a horse higher from the ground which is marked by the considerable height at chest but with very poor limbs, as shown by the low measurements found in its knee perimeters and cannon bone circumference with respect to those obtained by the authors consulted. This fact also is shown in the scores for the limbs where the average was inferior to the other six regional evaluations. Nevertheless, when we compare the average obtained for the total points with those of Valera (1997) for the 23 405 animals evaluated up to 1991, we can see that our punctuation (75.23) is higher by two points. Such an incongruency makes us think that there exists in recent years a search for horses higher off the ground, eumetric and of greater body size, even though one of the present problems of the Andalusian Horse, that of ‘poor’ limbs, remains unsolved.

4.2. Genetic parameters The genetic parameters of the equine traits have not been very well studied in comparison with other species, a fact even more patent in reference to

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non-functional traits, as in the case of zoometric body measurements and morphological evaluations of temperament or racial fidelity. The heritabilities obtained for the zoometric measures were of a medium-high magnitude ranging between 0.35 and 0.95. It is the height of the withers that is most studied by other authors. The value obtained in our population (0.5960.14) is similar to that found by Costa et al. (1998) in the Brazilian Pony population (0.52), Velea and Marcu (1978) in the Arabian horse (0.61) and Lippizzan horse (0.65) and that found by Von Butler (1987) in the Bavarian Heavy Horse (0.5560.19). Nevertheless, there exist many fluctuations in this measurement, having found in the bibliography values above 0.75 (Arnason, 1979; Van Bergen and Van Arendonk, 1993; Miglior et al., 1998; Saastamoinen et al., 1998a) and values below 0.37 (Varo, 1965; Georgescu et al., 1979; Silvestrelli et al., 1989, 1993; Koenen et al., 1995). For the heart girth circumference the heritability obtained was similar to Kalmykov (1973) in the Orlov Trotter (0.46–0.60) and Velea and Marcu (1978) in the Lippizzan horse (0.61). For chest width the heritability obtained was similar to Saastamoinen et al. (1998a) in the Finnhorse Trotter. Those found by other authors were clearly lower (Von Butler, 1987; Van Bergen and Van Arendonk, 1993; Costa et al., 1998). Even supposing the existence of a slight over estimation, very frequent in horse estimates, the moderate to high heritabilities obtained for the body measures indicate that a genetic improvement of these traits would be practical. This fact has a double importance: • On one hand, a legal requisite exists that demands that horses considered as fit for being reproducers have to meet certain minimum measurements (height at withers, height at chest, so on . . . ) by which a selection by independent levels of rejection is indirectly being carried out. • On the other hand, in the future selection and improvement plan for the Andalusian Horse, the incorporation of those zoometric measurements which are considered important to improve or to correct is feasible. This way we could emphasise the cannon bone circumference, especially important in our horse because frequently it shows its defects in leg-stance and in articulation prob-

lems due to the thinness of the limbs. It must be remembered that presently a high percentage of animals considered unfit by Committees of Evaluation are suffering from the ‘shank defect’. The heritability found by Silvestrelli et al. (1989, 1993) in the Maremmano Horse for this defect was 0.24. Perhaps the lesser value of heritability for this trait (0.35) with relation to the rest of the zoometric variables is an indication of the problem for its correction through selection, especially comparing this value with those obtained in the Maremmano Horse (Silvestrelli et al., 1989, 1993), in the Russian Heavy horse (Gorbukov and Gladenko, 1979), in the Orlov Trotter (Kalmykov, 1973) and those in the Finnhorse Trotter (Saastamoinen et al., 1998a). However this fact may also be a reflex of a selection, at least mass selection, during the last decades. The genetic and phenotypic correlations obtained were all positive, ranging from low to very high, in most cases high. The genetic correlation between the body measurements were moderate to high. This result agrees with Saastamoinen et al. (1998b) in the Finnhorse Trotter. Of the 21 correlations obtained among the seven zoometric measures, it is clear that the highest values were obtained between the measurements of height with length or thoracic capacity (0.94 between height at chest and heart girth circumference, 0.82 between height at chest and body length and 0.77 between body length and heart girth circumference). This fact shows the search on the part of Andalusian Horse Breeders, of proportioned animals for whom the aesthetic beauty of the horse is above the other qualities of a functional nature. The same occurs, for example, in the Brasileiro Pony (Costa et al., 1998). Also, through the genetic correlations, one of the problems existing in the Andalusian Horse is shown, its weakness in its limbs, since the correlations of the perimeter of the knee and the perimeter of the shank with the rest of the body measurements are smaller. Analysing the estimates obtained for the regional morphological evaluation, we can see that overall they show an appreciatively lower value than the zoometric measures, perhaps due to being subjected to a greater subjectivity and level of complexity. Nevertheless, the existence of heritability values of nearly 0.5 would support considering these estimates

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slightly biased (overestimated). In horses, conformation traits are mostly classified on a subjective scale and the linear system has been introduced recently. In the case of the conformation traits we consider that it is necessary to develop in this breed the linear type traits, like it is being used in many others horse breeds. The interest that these variables have in the Andalusian Horse is more than evident, not only because of the morphological importance in the sale price of these animals (much more appreciable in our horse than in other breeds with a clearer functional fitness) but also because of the relationship that exists between morphology and functional traits in any breed. In this sense, we should emphasise the score for limbs-stance (one of the lowest heritabilities of the group) for the reasons previously analysed and the scores for the withers, the back and the chest-thorax (with heritabilities between 0.4 and 0.5) for being considered the most important anatomical regions in any horse sports discipline. Nevertheless, in spite of the fact that the h 2 for limbs and stance is relatively low in comparison with the other morphological evaluations, it is superior to those found by Von Butler (1987), Van Bergen and Van Arendonk (1993), Koenen et al. (1995), Samore et al. (1997); Saastamoinen et al. (1998a). This same situation is true for the evaluation of racial fidelity and overall forms where the h 2 in the Andalusian Horse is higher than 0.5, in contrast to the values obtained by authors such as Von Butler (1987) and Preisinger et al. (1991), Samore et al. (1997), and Miglior et al. (1998) with heritabilities average 0.35. The scoring system presently in use includes several traits which mutually show high genetic correlations. When a high correlation between two traits exists, from a genetic point of view, almost no new information will be added by judging the second trait. Principal component analysis (Arnason, 1984) can be used to concentrate the available information in a reduced number of factors. This method can be used to consider if omission of some traits in the scoring system can be justified. However, reduction of the number of scored traits in practice will not be likely, as an extensive scoring report is highly appreciated by individual breeders. As for the correlations among the regional evaluations, the highest genetic correlations were obtained

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between the score of the limbs and stance with the score of the withers (0.91) and with the score of the chest-thorax (0.83). These high genetic correlations may be due to the influence that both the withers zone and the part of the chest and thorax exercise in the fore limbs of the Andalusian horse where a series of morphologic and locomotive qualities for the performance of the well-known ‘Spanish step’ is sought (the animal advances raising its forearm until it is parallel to the ground and afterwards extends the rest of the limb until all is parallel to the ground). Nevertheless, we could not determine the degree of influence that was exercised on the hind legs. The estimates obtained in the Swedish Ardenner horse by Erikison et al. (1998) were also positive and of the same magnitude. As for the following group of variables, the low heritabilities in the score for temperament and score for movement agree with the fact that not only are they the most subjective, most complex traits (being traits closely tied to behaviour), but it shows the greater relative weight of the environment. In spite of the fact that the estimates cited by Barrey (1992) were very high (0.61, 0.63 and 0.67 for scores in movements of walking, trotting and galloping, respectively), although other authors have obtained lower heritabilities (less than 0.40) (Varo, 1965; Von Butler, 1987; Chico and Langlois, 1990; Preisinger et al., 1991; Van Bergen and Van Arendonk, 1993; Oki et al., 1995; Saastamoinen et al., 1998a; Koenen et al., 1995; Miglior et al., 1998). In these non-genetic factors, training has a special importance, and it’s hard to separate in most of the cases from the rest of the effects. The value obtained for the score for temperament is similar to that found by Samore et al. (1997) of 0.02 to 0.06, although Von Butler (1987) shows an average value of around 0.25. Lastly, the heritability of the overall score trait, which includes all the previous ones indirectly, shows an intermediate magnitude. For this last group of evaluations we only obtained convergence for the score of overall forms and the movement score (0.55) and with the total score (0.74), which again shows the big influence that the overall morphology of the horse training in functional evaluation and, consequently in the total evaluation. These results agree with those obtained in other horse populations such as the Maremmano horse (Silvestrelli et al., 1989, 1993), the Trakehner

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(Preisinger et al., 1991), the Shetland Ponies (Van Bergen and Van Arendonk, 1993) and the Italian Haflinger (Miglior et al., 1998). In conclusion, and considering our results, measurements have greater heritability than subjective scoring. The heritability for zoometric measurements varied from moderate to very high, while the heritability for scored regional morphological conformation, racial fidelity and overall forms, and movements, varied from very low to intermediate. The moderate to high heritabilities obtained indicate that a genetic improvement of these traits would be practical. In the case of the conformation traits we consider that it is necessary to develop in this breed the linear type traits, like is being used in many others horse breeds. As for phenotypic and genetic correlations between variables in each group, all results were positive, and, in general, of great magnitude. These results are very important to define the selection objectives because they permit an indirect improvement of other correlated traits and not included in the improvement programme.

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