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Abstract In order to understand the characteristics of genetic resources of Kazakh horses in Xinjiang， their body size， phenotypes and coat colors were investigated and analyzed using the methods of resources survey and body size measurement. The results showed that the coat color of Kazakh horses in Xinjiang is very rich， covering more than 90% of the worlds horse coat colors. The influencing factors of Kazakh horse body size data might include the environment and geographical distribution of Kazakh horses. The gap between Xinjiang Kazakh horse and Kazakhstan Kazakh horse was relatively large， which was related to the degree of breeding. There were some differences in the appearance of Kazakh horses between Altay and Ili regions with different ecological environment. The Kazakh horses in Altay were relatively strong in size， well developed in coat and long hair， long and dense in fuzz in winter， and rich in coat color. But the Kazakh horses in Ili were compact in size， less in coat than those in Altay， and have a single coat color.
Key words Kazakh horse； Genetic resources； Characteristics； Coat color； Body size； Phenotype
Xinjiang is the province with the most abundant horse species and resources in China. For both the development of national economy and the inheritance of culture， horses have played an indispensable role in Xinjiang. Horses in ancient times were very important tools in warfare， communication and cultural exchange， as well as the development of agriculture and animal husbandry[1-2]. Xinjiang is divided into north and south， and there are great differences between the north and the south in terms of climate and geographical environment. In this different ecological environment， there are many livestock resources with local characteristics， which include many local horse breeds. However， there are only 4 local horse breeds in Xinjiang approved by the National Variety Approval Committee. They are Kazakh horse， Yanqi horse， Balikun horse and Kyrgyz horse. In Xinjiang， there are also two horse breeds， Yili horse and Yiwu horse， which are bred based on Kazakh horses. In the development of the horse industry in Xinjiang， the six horse breeds have made great contributions. They all have remarkable ecological environment adaptability and unique excellent traits[3].
Kazakh horses are mainly distributed in the north of the Tianshan Mountains， Altay， Ili and Tacheng in Xinjiang， as well as overseas Kazakhstan， Mongolia and so on. Xinjiangs Kazakh horse is a relatively old breed of horse that has been formed through long-term breeding of Kazak people， with its own characteristics， which are mainly formed after long-term domestication and cultivation. The Kazakhs are nomadic people and the Kazakh horses they breed are very adaptable to terrain such as cold mountains. According to statistics， the current population of Kazakh horses in Xinjiang accounts for about 10% of the total number of existing horses in China. The body of Kazakh horses belongs to the rough and strong type， with the ecological characteristics of herds. It is relatively heavy and has a good dual-use structure. Kazakh horses also have good milk performance[4]. They belong to prairie horses and are able to adapt to the continental drought and cold climate. In extremely harsh winter conditions， they are able to look for food in snow with depth of 20-40 cm. But in the summer， they recover strength quickly. Under the grazing conditions， October-November is the best time for Kazakh horses. It is usually the best season for fat accumulation of Kazakh horses. Usually， the period from November to December is the best time for slaughtering Kazakh horses[5]. Kazakh horses have many coat colors， dominated by red horses with black mane and tail. There are also grey， bay， black， white， roan and spotted horses. According to the statistical data of body size and appearance of adult Kazakh horses in Ili in 1981， the average body height， body length， chest circumference and cannon circumference of the adult Kazakh stallions were 139.8， 143.6， 168.8 and 18.8 cm respectively， and those of the adult Kazakh mares were 132.9， 136.8， 159.1 and 16.5 cm respectively. Compared with the statistical data of Kazakh horses in Kazakhstan in 1983， it could be found that the Kazakh horses in the two countries have great differences. Kazakhstan has attached great importance to breeding of Kazakh horses， and many local horse breeds are bred based on Kazakh horses. At present， in Xinjiang， the identification standard for Kazakh horses is not yet clear. In the future， a lot of energy should be invested in related research to provide a strong theoretical basis for the protection of local horse breeds. Materials and Methods
Experimental animal and apparatus and supplies
During 2015-2016， the coat color of total 104 （44 adult stallions and 60 adult mares） Kazakh horses in Altay， Tacheng and Ili regions of Xinjiang was surveyed. The body size of 2 000 Kazakh horses in four townships of Fuhai County in Altay Prefecture was measured. The horses were 2-10 years old， and the proportion of each age was almost the same.
The used instruments included rod， tape measures， notebook， camera， etc.
Measured items
The phenotypic traits of horses mainly include the description of body appearance and measurement of body size. Only the horses coat color and other characteristics can be observed with the naked eyes. Body size measurement refers to measuring the size of all parts of the horses using measuring tools. When measuring， the individual to be measured maintained an upright posture in a flat place. Usually， the measurer stands on the left side of the measured horses.
（1） Body height： The height of the straight line from the top of the withers to the ground.
（2） Body length： Oblique liner distance from shoulder to hip.
（3） Chest circumference： Vertical circumference of the body passing through the posterior edge of the scapulas. When the index finger and the middle finger could be inserted into， the looseness was considered appropriate.
（4） Cannon circumference： Circumference of the lower end of the top one third of the left forelimb， usually the perimeter of the smallest part of the cannon.
Data statistics and analysis
Means and standard deviations of body height， body length， chest circumference and cannon circumference of the horses were calculated using Excel. In the resources survey， the phenotypic differences of Kazakh horses between Altay and Ili were analyzed. The coat color of the Kazakh horses was analyzed and photographed.
Results and Analysis
Phenotypic differences of Kazakh horse
There is not much difference in the appearance of Kazakh horse between Xinjiang and Kazakhstan. However， in the resources survey in Xinjiang， it was found that the appearance of the Kazakh horse in the Altay area is quite different from that of the Kazakh horse in the Ili area. The phenotypic differences were as follows. The coat color of Kazakh horses in Ili area is relatively sample， the body is strong and dry， the mane， tail and fetlock hair is relatively less， the chest circumference is larger， and the adaptability to the cold winter is strong. The Kazakh horses in the Altay region are rich in coat color and have a rough and strong body， knife-like hindlimbs， and developed mane， tail and fetlock hair. They are mainly used for riding （Table 1）. Statistics on coat color of Kazakh horse
The classification of coat color of horses in China and abroad is shown in Table 2. During the resources survey in Xinjiang in 2015-2016， it was found that the coat color of Kazakh horses in Xinjiang is very rich and can be divided into several categories according to different classification criteria. These categories almost include all the coat colors described in Cui Yuxis Hippology.
As shown in Table 2， China and foreign countries have different method of classifying horses coat color， and the categories of coat color are also different. The coat color of Kazakh horses in Kazakhstan is most abundant. Due to language restrictions， many classifications of horsehair in Kazakhstan have not been translated.
Statistics on body size of Kazakh horse
The data about body size of Kazakh horses in various townships of Fuhai County， Altay Prefecture are shown in Table 3. The data about body size of adult Kazakh horses in China over the years are shown in Table 4.
The data about body size of Kazakh horses in 1981 were quoted from Ili Livestock and Poultry Resources， and the Kazakh horses mainly refer to those in the Ili region. Therefore， they cannot represent the body size of Kazakh horses in Xinjiang. In 2008， Modern Horse Studies and The Production Management of Horses all stated the body size data of Kazakh horses. There are big differences between the two. The two books do not explain in detail the distribution range and age of Kazakh horses， and cannot accurately explain the changes in the body size of Kazakh horses. In this survey， the adult Kazakh horses in the Altay region of Xinjiang were measured. From the data shown in Table 3， it could preliminarily concluded that the differences in Kazakh horses living environment and geographical location will lead to inconsistent data on the body size.
The body height， body length， chest circumference and cannon circumference of adult Kazakh stallions in Kazakhstan in 1983 were 141， 149， 178 and 18.7 cm respectively， and those of adult mares were 139， 145， 168 and 17.9 cm respectively[6-7]. According to the body size data of Kazakhstans Kazakh horses， it can be seen that he body height， body length and chest circumference of Kazakh horses in Kazakhstan in 1983 are significantly higher than those in 1981. The body size data of Kazakh stallions in Altay region of Xinjiang in 2015 are similar to those in Kazakhstan in 1983. Discussion and Conclusions
In the process of resources survey， it was found that the Kazakh horses in Xinjiang and Kazakhstan have similar physical characteristics， and there is not much difference. The coat colors of Kazakh horses in Xinjiang are complete， covering almost all of the coat colors described by Cui Yuxis Hippology. The Kazakh horse in Xinjiang belongs to a relatively old breed of horse， and its genetic diversity is richer than other horse breeds in Xinjiang. The rich coat colors also illustrate this conclusion. In terms of classification of coat color， there are some differences between China and foreign countries. In China， the coat color of horses is divided into 13 categories and 33 kinds； In Kazakhstan， the coat color of horses is divided into 14 categories and 203 kinds； while in other countries， the coat color of horses is divided into 4 categories and 53 kinds. In the process of statistics on the coat color of Kazakh horses， it was also found that the coat color of some horses changes during foal， adult and old ages. The related molecular mechanisms need further study.
In 1981， the body size of Kazakh horses in Ili region is significantly smaller than that in Kazakhstan. The reason is that Kazakh horse in Kazakhstan is also an ancient breed and is usually used as a basic breed for the cultivation of other horse breeds， and Kazakhstan has paid more attention to the cultivation of horse breeds. However， Xinjiang places relatively little emphasis on local horse breeds. Many local breeds of horses are only breeding in herdsmens homes. They are not hybridized with exotic horses and have not been improved. There is no clear measurement range and age in the two data in 2008， which are impossible to accurately explain the changes in the body size of Kazakh horses. The measurement data of the Kazakh stallions in the Altay region of Xinjiang in 2015 is similar to that of the Kazakh stallions in Kazakhstan in 1983， indicating that there is still very large space for improvement of body height in Kazakh horse breeding.
It was also found in this resources survey that the phenotypes of Kazakh horses in the Altay and Ili regions of Xinjiang are very different. The Kazakh horses in the Ili area have relatively simple coat color， strong and dry body， less mane， tail and fetlock hair， and large chest circumference， while the Kazakh horses in the Altay region are rich in coat color， rough and strong in physique， knife-like in limbs， and developed in mane， tail and fetlock hair. This may be due to different historical backgrounds and geography that cause Kazakh horses to have different appearance in different regions. Phenotypic variation is part of the genetic diversity of the population studied. In this study， the genetic resources of Kazakh horses in different regions of Xinjiang were surveyed， and the results will provide a theoretical basis for the future protection of local horse breeds. There are no uniform standards for the classification of Kazakh horses throughout Xinjiang. In some areas， the Kazak peoples horses are considered to be Kazakh horses. But in other areas， the horses with shorter height are considered to be Kazakh horses. Therefore， the criteria for identifying Kazakh horse must be further studied.
References
[1] KELEKNA P. The horse in human history[M]. New York：Cambridge University Press，2009.
[2] CIESLAK M，PRUVOST M， BENECKE N， et al. Origin and history of mitochondrial DNA lineages in domestic horses [J]. PLoS One，2010，5（12）： 15311-15315.
[3] LI ZJ. Analysis of genetic diversity of three horse breeds by STR [D]. Urumqi： Xinjiang Agricultural University， 2013. （In Chinese）
[4] YAO XK， HAN GC. Horse Production Management [M]. Beijing： China Agricultural University Publishing Society， 2008. （In Chinese）
[5] Comparative analysis of production performance of Kazakh horses. China Herbivores， 2011， 31（2）： 69-71. （In Chinese）
[6] CANON J， CHECA M L， CARLEOS C，et al. The genetic structure of Spanish Celtic horse breeds inferred from microsatellite data [J]. Animal Genetics， 2000，31（1）： 39-48.
[7] KELLY L， POSTIGLIONI A， DE ANDRES DF， et al. Genetic characterisation of the Uruguayan Creole horse and analysis of relationships among horse breeds [J]. Research in Veterinary Science， 2002， 72 （1）： 69-73.
Key words Kazakh horse； Genetic resources； Characteristics； Coat color； Body size； Phenotype
Xinjiang is the province with the most abundant horse species and resources in China. For both the development of national economy and the inheritance of culture， horses have played an indispensable role in Xinjiang. Horses in ancient times were very important tools in warfare， communication and cultural exchange， as well as the development of agriculture and animal husbandry[1-2]. Xinjiang is divided into north and south， and there are great differences between the north and the south in terms of climate and geographical environment. In this different ecological environment， there are many livestock resources with local characteristics， which include many local horse breeds. However， there are only 4 local horse breeds in Xinjiang approved by the National Variety Approval Committee. They are Kazakh horse， Yanqi horse， Balikun horse and Kyrgyz horse. In Xinjiang， there are also two horse breeds， Yili horse and Yiwu horse， which are bred based on Kazakh horses. In the development of the horse industry in Xinjiang， the six horse breeds have made great contributions. They all have remarkable ecological environment adaptability and unique excellent traits[3].
Kazakh horses are mainly distributed in the north of the Tianshan Mountains， Altay， Ili and Tacheng in Xinjiang， as well as overseas Kazakhstan， Mongolia and so on. Xinjiangs Kazakh horse is a relatively old breed of horse that has been formed through long-term breeding of Kazak people， with its own characteristics， which are mainly formed after long-term domestication and cultivation. The Kazakhs are nomadic people and the Kazakh horses they breed are very adaptable to terrain such as cold mountains. According to statistics， the current population of Kazakh horses in Xinjiang accounts for about 10% of the total number of existing horses in China. The body of Kazakh horses belongs to the rough and strong type， with the ecological characteristics of herds. It is relatively heavy and has a good dual-use structure. Kazakh horses also have good milk performance[4]. They belong to prairie horses and are able to adapt to the continental drought and cold climate. In extremely harsh winter conditions， they are able to look for food in snow with depth of 20-40 cm. But in the summer， they recover strength quickly. Under the grazing conditions， October-November is the best time for Kazakh horses. It is usually the best season for fat accumulation of Kazakh horses. Usually， the period from November to December is the best time for slaughtering Kazakh horses[5]. Kazakh horses have many coat colors， dominated by red horses with black mane and tail. There are also grey， bay， black， white， roan and spotted horses. According to the statistical data of body size and appearance of adult Kazakh horses in Ili in 1981， the average body height， body length， chest circumference and cannon circumference of the adult Kazakh stallions were 139.8， 143.6， 168.8 and 18.8 cm respectively， and those of the adult Kazakh mares were 132.9， 136.8， 159.1 and 16.5 cm respectively. Compared with the statistical data of Kazakh horses in Kazakhstan in 1983， it could be found that the Kazakh horses in the two countries have great differences. Kazakhstan has attached great importance to breeding of Kazakh horses， and many local horse breeds are bred based on Kazakh horses. At present， in Xinjiang， the identification standard for Kazakh horses is not yet clear. In the future， a lot of energy should be invested in related research to provide a strong theoretical basis for the protection of local horse breeds. Materials and Methods
Experimental animal and apparatus and supplies
During 2015-2016， the coat color of total 104 （44 adult stallions and 60 adult mares） Kazakh horses in Altay， Tacheng and Ili regions of Xinjiang was surveyed. The body size of 2 000 Kazakh horses in four townships of Fuhai County in Altay Prefecture was measured. The horses were 2-10 years old， and the proportion of each age was almost the same.
The used instruments included rod， tape measures， notebook， camera， etc.
Measured items
The phenotypic traits of horses mainly include the description of body appearance and measurement of body size. Only the horses coat color and other characteristics can be observed with the naked eyes. Body size measurement refers to measuring the size of all parts of the horses using measuring tools. When measuring， the individual to be measured maintained an upright posture in a flat place. Usually， the measurer stands on the left side of the measured horses.
（1） Body height： The height of the straight line from the top of the withers to the ground.
（2） Body length： Oblique liner distance from shoulder to hip.
（3） Chest circumference： Vertical circumference of the body passing through the posterior edge of the scapulas. When the index finger and the middle finger could be inserted into， the looseness was considered appropriate.
（4） Cannon circumference： Circumference of the lower end of the top one third of the left forelimb， usually the perimeter of the smallest part of the cannon.
Data statistics and analysis
Means and standard deviations of body height， body length， chest circumference and cannon circumference of the horses were calculated using Excel. In the resources survey， the phenotypic differences of Kazakh horses between Altay and Ili were analyzed. The coat color of the Kazakh horses was analyzed and photographed.
Results and Analysis
Phenotypic differences of Kazakh horse
There is not much difference in the appearance of Kazakh horse between Xinjiang and Kazakhstan. However， in the resources survey in Xinjiang， it was found that the appearance of the Kazakh horse in the Altay area is quite different from that of the Kazakh horse in the Ili area. The phenotypic differences were as follows. The coat color of Kazakh horses in Ili area is relatively sample， the body is strong and dry， the mane， tail and fetlock hair is relatively less， the chest circumference is larger， and the adaptability to the cold winter is strong. The Kazakh horses in the Altay region are rich in coat color and have a rough and strong body， knife-like hindlimbs， and developed mane， tail and fetlock hair. They are mainly used for riding （Table 1）. Statistics on coat color of Kazakh horse
The classification of coat color of horses in China and abroad is shown in Table 2. During the resources survey in Xinjiang in 2015-2016， it was found that the coat color of Kazakh horses in Xinjiang is very rich and can be divided into several categories according to different classification criteria. These categories almost include all the coat colors described in Cui Yuxis Hippology.
As shown in Table 2， China and foreign countries have different method of classifying horses coat color， and the categories of coat color are also different. The coat color of Kazakh horses in Kazakhstan is most abundant. Due to language restrictions， many classifications of horsehair in Kazakhstan have not been translated.
Statistics on body size of Kazakh horse
The data about body size of Kazakh horses in various townships of Fuhai County， Altay Prefecture are shown in Table 3. The data about body size of adult Kazakh horses in China over the years are shown in Table 4.
The data about body size of Kazakh horses in 1981 were quoted from Ili Livestock and Poultry Resources， and the Kazakh horses mainly refer to those in the Ili region. Therefore， they cannot represent the body size of Kazakh horses in Xinjiang. In 2008， Modern Horse Studies and The Production Management of Horses all stated the body size data of Kazakh horses. There are big differences between the two. The two books do not explain in detail the distribution range and age of Kazakh horses， and cannot accurately explain the changes in the body size of Kazakh horses. In this survey， the adult Kazakh horses in the Altay region of Xinjiang were measured. From the data shown in Table 3， it could preliminarily concluded that the differences in Kazakh horses living environment and geographical location will lead to inconsistent data on the body size.
The body height， body length， chest circumference and cannon circumference of adult Kazakh stallions in Kazakhstan in 1983 were 141， 149， 178 and 18.7 cm respectively， and those of adult mares were 139， 145， 168 and 17.9 cm respectively[6-7]. According to the body size data of Kazakhstans Kazakh horses， it can be seen that he body height， body length and chest circumference of Kazakh horses in Kazakhstan in 1983 are significantly higher than those in 1981. The body size data of Kazakh stallions in Altay region of Xinjiang in 2015 are similar to those in Kazakhstan in 1983. Discussion and Conclusions
In the process of resources survey， it was found that the Kazakh horses in Xinjiang and Kazakhstan have similar physical characteristics， and there is not much difference. The coat colors of Kazakh horses in Xinjiang are complete， covering almost all of the coat colors described by Cui Yuxis Hippology. The Kazakh horse in Xinjiang belongs to a relatively old breed of horse， and its genetic diversity is richer than other horse breeds in Xinjiang. The rich coat colors also illustrate this conclusion. In terms of classification of coat color， there are some differences between China and foreign countries. In China， the coat color of horses is divided into 13 categories and 33 kinds； In Kazakhstan， the coat color of horses is divided into 14 categories and 203 kinds； while in other countries， the coat color of horses is divided into 4 categories and 53 kinds. In the process of statistics on the coat color of Kazakh horses， it was also found that the coat color of some horses changes during foal， adult and old ages. The related molecular mechanisms need further study.
In 1981， the body size of Kazakh horses in Ili region is significantly smaller than that in Kazakhstan. The reason is that Kazakh horse in Kazakhstan is also an ancient breed and is usually used as a basic breed for the cultivation of other horse breeds， and Kazakhstan has paid more attention to the cultivation of horse breeds. However， Xinjiang places relatively little emphasis on local horse breeds. Many local breeds of horses are only breeding in herdsmens homes. They are not hybridized with exotic horses and have not been improved. There is no clear measurement range and age in the two data in 2008， which are impossible to accurately explain the changes in the body size of Kazakh horses. The measurement data of the Kazakh stallions in the Altay region of Xinjiang in 2015 is similar to that of the Kazakh stallions in Kazakhstan in 1983， indicating that there is still very large space for improvement of body height in Kazakh horse breeding.
It was also found in this resources survey that the phenotypes of Kazakh horses in the Altay and Ili regions of Xinjiang are very different. The Kazakh horses in the Ili area have relatively simple coat color， strong and dry body， less mane， tail and fetlock hair， and large chest circumference， while the Kazakh horses in the Altay region are rich in coat color， rough and strong in physique， knife-like in limbs， and developed in mane， tail and fetlock hair. This may be due to different historical backgrounds and geography that cause Kazakh horses to have different appearance in different regions. Phenotypic variation is part of the genetic diversity of the population studied. In this study， the genetic resources of Kazakh horses in different regions of Xinjiang were surveyed， and the results will provide a theoretical basis for the future protection of local horse breeds. There are no uniform standards for the classification of Kazakh horses throughout Xinjiang. In some areas， the Kazak peoples horses are considered to be Kazakh horses. But in other areas， the horses with shorter height are considered to be Kazakh horses. Therefore， the criteria for identifying Kazakh horse must be further studied.
References
[1] KELEKNA P. The horse in human history[M]. New York：Cambridge University Press，2009.
[2] CIESLAK M，PRUVOST M， BENECKE N， et al. Origin and history of mitochondrial DNA lineages in domestic horses [J]. PLoS One，2010，5（12）： 15311-15315.
[3] LI ZJ. Analysis of genetic diversity of three horse breeds by STR [D]. Urumqi： Xinjiang Agricultural University， 2013. （In Chinese）
[4] YAO XK， HAN GC. Horse Production Management [M]. Beijing： China Agricultural University Publishing Society， 2008. （In Chinese）
[5] Comparative analysis of production performance of Kazakh horses. China Herbivores， 2011， 31（2）： 69-71. （In Chinese）
[6] CANON J， CHECA M L， CARLEOS C，et al. The genetic structure of Spanish Celtic horse breeds inferred from microsatellite data [J]. Animal Genetics， 2000，31（1）： 39-48.
[7] KELLY L， POSTIGLIONI A， DE ANDRES DF， et al. Genetic characterisation of the Uruguayan Creole horse and analysis of relationships among horse breeds [J]. Research in Veterinary Science， 2002， 72 （1）： 69-73.