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Research Article
 

Genetic and Environmental Parameters Effecting Racing Performance of Turk-Arabian Horses Raised at Anatolian State Farm



H. Orhan and A. Kaygisiz
 
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ABSTRACT

In this study, some environmental factors and genetic parameters affecting performance of racing for Turk-Arabian horses at different distances raised at Anatolian Agricultural Farms were investigated. In the experiment, 3184 race records of 437 offspring of 32 horses races from 1996 to 2008 were evaluated by two statistical models. The effects of year, hippodrome, track and distance on racing time and race speed were found highly significant (p<0.01). Genetic parameters were estimated by REML procedure using DFREML program. Estimated heritabilities of race finishing times ranged from 0.106 to 0.044 and estimated repeatability from 0.714 to 0.233. Results indicated that a moderate level of genetic progress is possible for racing time if selection is based on the phenotypic value of the horses. For short and medium distance horse breeding values, calculated spearman correlation (0.26) was not significant (p>0.05). This should be taken into account in the breeding program, since the short and medium distance running abilities of horses were independent. In addition, runway type should be considered for estimation of the breeding values. Model-1 and Model-2 provided similar results for racing time. Model-1 (full model) may be preferred to Model-2 as interpretation of racing time abilities for all the factors available via Model-1.

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  How to cite this article:

H. Orhan and A. Kaygisiz, 2010. Genetic and Environmental Parameters Effecting Racing Performance of Turk-Arabian Horses Raised at Anatolian State Farm. Asian Journal of Animal and Veterinary Advances, 5: 112-119.

DOI: 10.3923/ajava.2010.112.119

URL: https://scialert.net/abstract/?doi=ajava.2010.112.119
 

INTRODUCTION

Arabian horse race is one of the most important warm-blooded horse races. Arabian horses get attention due to the harmony of morphological structure of their body. They have small head, large and dry eyes and small and upright ears. Their foreheads are broad and they have generally smooth profile. Hip heights of these horses usually range from 145 to 160 cm. They have soft, thin skin and smooth, shiny and short hairs. Their coat colors are usually Chestnuts (copper color), grey or bay. Dark (horse) coat is rare. During gallop, their tails stand up, making a curve which is called as hold queue. Arabian horses have solid bodies and have different good abilities such as ride, freightage and racing. The heritability’s of these characters are high. These horses get mature by the age of four. Turk-Arabian horse breeding in Turkey is conducted by the Turkish government in Bursa, Eskişehir and Malatya. Those horses are grown and bred since, mid times of ottoman Empire by a Anatolian farm located in Malatya. Horse breeding in the farm is an example for the region and other parts of Turkey and is considered as a horse breeding center of Turkey. Officially, horse races in Turkey are organized by Turkish Jockey Club (TJK) in İstanbul, Ankara, Bursa, İzmir and Şanlıurfa (Ekiz et al., 2005a).

The racing performance of horses is affected by environmental factors such as hippodrome track (sand or turf), distance and year. Sand makes racing condition hard, thus the races held in sand track are more difficult for horses than the races held in turf track. But sand track requires more power and endurance (Koseman, 2005).

Determination of the environmental effects and the estimation of genetic parameter effecting race performance is important in optimization of selection programs. The heritability values of racing performance parameters usually range from low to high and the repeatability are usually medium and high (Ekiz et al., 2005a).

Restricted maximum likelihood (RELM) method has been extensively used to estimate genetic parameters and variance components. The REML method has the most desirable statistical properties for estimation of variance components (Ekiz and Kocak, 2007; Ekiz et al., 2005a, b; Bakhtiari and Kashan, 2009).

The reported heritability estimates in the literature for racing time generally ranged from low to moderate (Ekiz and Kocak, 2007; Ekiz et al., 2005a, b; Bakhtiari and Kashan, 2009; Mota, 2006; Koseman, 2005). Ekiz et al. (2005b) reported moderate to high heritability estimates of 0.465, 0.293 and 0.359 for racing time of Thoroughbred horses at dirt, turf and combination of both tracks. Ekiz and Kocak (2007) estimated heritability for Thoroughbred horses to be 0.177 to 0.353 and 0.289 to 0.404, respectively depending on the racing distances 1200 to 2400 m. Bakhtiari and Kashan (2009) estimated heritability for Iranian Thoroughbred horses to be 0.13, 0.11 and 0.09 for distances 1000, 1400 and +1600 m, respectively.

These results indicated that a moderate level of genetic progress is possible for racing time if selection is based on the phenotypic value of the horses.

Race finishing time is a direct measure of speed and is regarded as the best method of the evaluation of race performance of horses (Ekiz and Kocak, 2005b; Oki et al., 1995; Mota et al., 2005).

Mota et al. (2005) reported the observed lowest and highest heritability 0.04 and 0.29 at 1500 and 1000 m races for racing time, respectively. And also lowest and highest repeatability were given 0.19 and 0.63 for the same distances, respectively. Bakhtiari and Kashan (2009) pointed out the repeatability estimates of racing time for 1000, 1400 and +1600 m were 0.26, 0.19 and 0.17, respectively.

The objective of this study was to investigate environmental effects that influence racing performance with using two statistical mathematics models and to estimate genetic parameters over various distances.

MATERIALS AND METHODS

Open and group races finishing time data from 1200, 1300, 1400, 1500, 1600, 1800, 1900, 2000, 2100, 2200 and 2400 m races belonging to years at 1996-2008 of the Arabian horses, grown by Anatolian Agricultural Institution, were obtained from Turkey Jokey Club records and used in this study.

The 3184 race records of 437 offspring of 32 horses were used in this study. Factor affecting race finishing time (racing time) and race speed such as year, the hippodrome (City), track, distance were evaluated. Two different models were used in the evaluation of research data. In model-1, year, hippodrome, track and race distance were included in the model affecting for racing time and race speed. In model-2, race distance factor were dropped the model and effects of other factors on racing time for each distance were investigated.

Mathematical models used in the analysis:

(Model-1)

(Model-2)

where, Yijkl(m) is racing time or race speed, μ is population mean, ai is ith. effect of year, bj is jth. effect of hippodrome, ck is kth. effect of track, dl is l. effect of race distance and eijkl(m) is random experimental error (normally distributed with mean zero and component of variance σ2e ).

For each model, to investigate the significance levels of factors on racing time and race speed, Analysis of Variance (ANOVA) was conducted using the GLM procedure of SAS package (Orhan et al., 2004).

Variance components and genetic parameters were estimated according to REML method by DFREML package (Meyer, 1997).

RESULTS AND DISCUSSION

Descriptive statistics and significant levels of racing time and race speed by factors included in the model-1 are given in Table 1. In terms of racing time and race speed, the effects of year, hippodrome, distance and track were found significantly (p<0.01) (Table 1). There are 2 types of racing tracks. In competitions, racing time was shorter and race speed was higher in turf tracks than dirt tracks. And also, racing time and race speed were both affected by hippodromes. The highest race speeds were observed in Istanbul and Ankara hippodrome, while the lowest race speeds were obtained in Şanlıurfa hippodrome.

Descriptive statistics and significant levels of racing time by factors included in the model-2 were shown in Table 2. In the overall evaluation of 13 year period, it was observed that race speed increased and racing time decreased.

In the separate analysis for each distance, the effects of the year and hippodrome were significant (p<0.01) for each distance and track effect was significant for all distances (p<0.01) except for 1500 m. Due to insufficient data, evaluations couldn’t be conducted for 1700 and 2800 m records distances (Table 2).

The variance components and genetic parameter estimates obtained for different race distances were shown in Table 3. The highest heritability for racing time was obtained from 1300 m (11.0%) while the lowest heritability was observed at 2200 m (4.0%). For overall race distances, the heritability was estimated as 5.0% which is considered to be low. Heritability and repeatability estimates tended to decrease with increasing distance, this indicating that selection based on racing time will be less successful.

In racing time, the highest repeatability (71.0%) was obtained in the 2200 m and the lowest repeatability (23.0%) was obtained in 1500 m. For overall race distances, racing time repeatability was estimated as 35.0% and interpreted as mid-high level.

In horse races, 800-1600 m races were classified as short distance and 1601-2400 m races were classified as medium distance races. The correlations coefficients calculated for breeding values of stallions between raced in short and medium races found 0.18, 0.26 and 0.18 by Pearson, Spearman and Kendal’s methods, respectively.

Table 1: Descriptive statistics, significance levels of race speed and racing time for Model-1
*: Significance level of ANOVA results, a-h: Means with the same letter(s) are not significantly different for race speed and racing time for each factor

Table 2: Racing time descriptive statistics and significance levels resulted for each distance by Model-2

Table 2: Continued

Table 2: Continued
N: No. of records, SE: Standard Error

Table 3: Estimated genotypic and phenotypic variances and parameter estimates for race speed for each racing distance (m)
σ2A: Additive genetic variance, σ2PE: Permanent environmental variance, σ2E: Error variance, σ2P: Phenotypic variance, h2: Heritability, P2e = σ2PE2P, r: Repeatability

Correlations between the estimated breeding values of stallions, which raced short and medium distance races, were found insignificantly (p>0.05).

DISCUSSION

The effect of the race track was significant both for race speed and racing time (p<0.01). Racing time on grass track was found shorter than in the sand track (Table 1, 2). Kocak and Ekiz (2005), Moritsu et al. (1994), Oki et al. (1995) and Mota et al. (1998) have reported similar results for Brazilian Thoroughbreds. Sand makes racing condition hard, thus the races held in sand track are more difficult for horses than the races held in turf track.

On the other hand, race finishing time showed significant differences according to the hippodromes where the races were held (p<0.01). Similar results have been reported by Bakhtiari and Kashan (2009).

The effect of year was found to be significant on the race performance (p<0.01). Over the years, race speed increased and race finishing time decreased. In terms of years, both environmental improvements and progress in the breeding selection improved race performance of horses. Ekiz and Kocak (2005) have reported that race performance affected by the year effect in Arabian horses. Also, similar findings have been mentioned by Kocak and Ekiz (2005) and Ekiz et al. (2005b) for thoroughbred horses.

Heritabilities of racing time varied according to race distances from 0.044 (2200 m) to 0.106 (1300 m). In general, heritability for racing times was low. In the Anatolian farm where the experimental data was obtained the number of breeding stock per year was about 8-9. The low number of breed-stocks for the reproduction purpose may lead decreased genetic variance, leading to low heritability values for racing times. On the other hand, the estimates of heritability and repeatability of racing time tended to decrease with increasing racing distance. Decreasing tendency in heritability could be due to the fact the racing speed could be lowered to the extend where the environmental conditions are changed by increased racing distance.

In the model-2 analysis, heritability for racing times was estimated as 0.0538. According to this, heritability belonging to the racing times was found to be higher in the shorter distances and lower for long distances. Similar result was expressed by Sobczynska (2006) and Mota et al. (2005).

Estimated heritabilities in this study were in agreement with the reports of Sobczynska (2006), Moritsu et al. (1994), Bakhtiari and Kashan (2009), Mota et al. (2005), Taveria et al. (2004). On the other hand, obtained heritability estimates in this study were lower than the values found by Ekiz and Kocak (2005), Lee et al. (1992), Park and Lee (1999), Oki et al. (1995) and Villela et al. (2002).

Observing Table 3, repeatabilities belonging to racing time varied according to race distances and ranged 0.233 (1500 m) to 0.626 (1300 m). In the analysis, without taking into account of the distance (Model-2), repeatability of racing times was estimated as 0.351. Estimated repeatabilities in this study were in agreement with the values of Park and Lee (1999) and Villela et al. (2002). On the other hand, obtained repeatability estimates in this study were lower than the values found by Oki et al. (1995) and were higher than the values found by Ekiz et al. (2005a, b), Bakhtiari and Kasan (2009) and Ekiz and Kocak (2007).

In this study, heritabilities were found to be low, while repeatabilities were found to be high in relation with race performance. Therefore, possibility of improvement by selection seemed limited. However, because of the high repeatabilities, selection could be done in the early ages.

Minimum and maximum race speeds were observed at 1800 (13:55 m sec-1) and 1200 m (14:29 m sec-1) races, respectively. Range of observed race speeds was 0.74 m sec-1. This range value was higher than 0.24 m sec-1 reported by Mota et al. (1998) and lower than 0.85 m sec-1 reported by Taveira et al. (2004).

Between breeding values of short and medium distances, in both categories which had 27 horse cubs, Pearson and Kendall correlation coefficients were found the same 0.18 and Spearman correlation coefficient was found 0.26. These correlation coefficients were lower than 0.35 reported by Moritsu et al. (1994) for between 1200 and 1800 m. Interpretations of these results, the short and medium distance running abilities of horses were independent of each other; therefore, this situation should be taken into account in the selection of breeding. Race distance and runway type should be taken into consideration for estimation of the breeding values. Model-1 and model-2 had given similar results for racing time. Model-1 (full model) may be preferred to Model-2. Because, interpretation of racing time abilities for all the factors (included in model-1) available via model-1.

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