1- Shahrekord University
2- Animal Science Research Institute
2- Animal Science Research Institute
Abstract: (25 Views)
Introduction and Objective: Given the increasing importance of identifying factors affecting the physical structure of sport horses and the critical role of biometric traits in determining their athletic performance and capabilities, this study investigated the effect of non-genetic and environmental factors (age, sex, and rearing region) on biometric traits of Thoroughbred horses in Golestan province, Iran. The Thoroughbred, as one of the most important sport horse breeds worldwide, possesses unique characteristics, and understanding the factors influencing its body dimensions can significantly contribute to optimizing its athletic performance. The main objective of this study was to determine and quantify the effects of three factors: age (as a physiological-developmental factor), sex (as a genetic-biological factor), and rearing region (as an environmental factor) on the biometric traits of this valuable breed. A precise understanding of these relationships can be highly important for breeding programs, management practices, and selection of suitable horses for racing competitions, ultimately leading to performance optimization in various equestrian disciplines.
Materials and Methods: In this study, biometric traits of 105 Thoroughbred horses (66 stallions and 39 mares) aged 2 to 4 years were measured following ethical principles. Samples were randomly collected from three horse-rearing counties in Golestan province: Gonbad Kavous (n=61), Aqqala (n=24), and Bandar Torkaman (n=20). All horses were assessed for general health, absence of apparent skeletal abnormalities, and desirable physical condition. Measurements were performed on a flat surface from the left side of each horse by a trained individual using a standard measuring tape. A total of 16 biometric traits were measured: head length, neck length, chest width, thorax girth, withers height, abdominal girth, body mid-height, umbilical girth, croup height, back length, body length, pelvis width, croup length, croup depth, tail-set height, and tail length. Statistical analyses included descriptive statistics (mean, standard deviation, minimum, maximum, coefficient of variation), analysis of variance (ANOVA), and comparison of least squares means using the General Linear Model (GLM). The statistical model included the fixed effects of age, sex, and rearing region. The normality of data distribution was confirmed for all 16 biometric traits across the different levels of the factors (age, sex, and rearing region). Mean comparisons were performed using the Tukey-Kramer test at a significance level of 5%. All statistical analyses were conducted using SAS software.
Findings: Descriptive statistics revealed that the highest coefficient of variation (CV) was estimated for croup length (8.81%) and the lowest for body mid-height (2.41%), indicating that croup length had the greatest variability while body mid-height showed the highest stability. As expected, age had a significant effect on six biometric traits: thorax girth (P<0.01), withers height (P<0.05), croup height (P<0.05), back length (P<0.01), body length (P<0.05), and tail-set height (P<0.05). Rearing region significantly affected nine traits: head length (P<0.01), neck length (P<0.01), chest width (P<0.01), thorax girth (P<0.01), back length (P<0.01), body length (P<0.05), pelvis width (P<0.01), tail-set height (P<0.01), and tail length (P<0.01). Horses reared in Bandar Torkaman were significantly superior in several traits, whereas those from Aqqala showed lower values in some traits. These differences are likely attributable to variations in environmental conditions, management practices, and feeding systems. However, sex showed no statistically significant effect on any of the biometric traits, although mean values tended to be higher in stallions than in mares, suggesting uniformity in management and training between sexes in the study region.
Conclusion: The results indicate that Thoroughbred horses in Golestan province exhibit relatively high mean values for several biometric traits compared to previously reported values for other Iranian breeds. However, caution is warranted as these comparisons are indirect due to differences in sampling conditions (e.g., age, sex, region, tools, and measurement methods). Among the studied factors, age and rearing region were identified as determinants of biometric trait variability. Specifically, a significant improvement was observed at 3 years of age in traits such as thorax girth, withers height, back length, body length, tail-set height, and croup height. Regional differences in traits such as neck length, chest width, and croup length highlight the influence of geographical conditions and management practices. Sex had no significant effect. Given the cross-sectional and phenotypic nature of this study, and the lack of genetic (pedigree) and performance (race record) data, direct application of these findings in breeding programs requires further genetic and performance-based studies.
Materials and Methods: In this study, biometric traits of 105 Thoroughbred horses (66 stallions and 39 mares) aged 2 to 4 years were measured following ethical principles. Samples were randomly collected from three horse-rearing counties in Golestan province: Gonbad Kavous (n=61), Aqqala (n=24), and Bandar Torkaman (n=20). All horses were assessed for general health, absence of apparent skeletal abnormalities, and desirable physical condition. Measurements were performed on a flat surface from the left side of each horse by a trained individual using a standard measuring tape. A total of 16 biometric traits were measured: head length, neck length, chest width, thorax girth, withers height, abdominal girth, body mid-height, umbilical girth, croup height, back length, body length, pelvis width, croup length, croup depth, tail-set height, and tail length. Statistical analyses included descriptive statistics (mean, standard deviation, minimum, maximum, coefficient of variation), analysis of variance (ANOVA), and comparison of least squares means using the General Linear Model (GLM). The statistical model included the fixed effects of age, sex, and rearing region. The normality of data distribution was confirmed for all 16 biometric traits across the different levels of the factors (age, sex, and rearing region). Mean comparisons were performed using the Tukey-Kramer test at a significance level of 5%. All statistical analyses were conducted using SAS software.
Findings: Descriptive statistics revealed that the highest coefficient of variation (CV) was estimated for croup length (8.81%) and the lowest for body mid-height (2.41%), indicating that croup length had the greatest variability while body mid-height showed the highest stability. As expected, age had a significant effect on six biometric traits: thorax girth (P<0.01), withers height (P<0.05), croup height (P<0.05), back length (P<0.01), body length (P<0.05), and tail-set height (P<0.05). Rearing region significantly affected nine traits: head length (P<0.01), neck length (P<0.01), chest width (P<0.01), thorax girth (P<0.01), back length (P<0.01), body length (P<0.05), pelvis width (P<0.01), tail-set height (P<0.01), and tail length (P<0.01). Horses reared in Bandar Torkaman were significantly superior in several traits, whereas those from Aqqala showed lower values in some traits. These differences are likely attributable to variations in environmental conditions, management practices, and feeding systems. However, sex showed no statistically significant effect on any of the biometric traits, although mean values tended to be higher in stallions than in mares, suggesting uniformity in management and training between sexes in the study region.
Conclusion: The results indicate that Thoroughbred horses in Golestan province exhibit relatively high mean values for several biometric traits compared to previously reported values for other Iranian breeds. However, caution is warranted as these comparisons are indirect due to differences in sampling conditions (e.g., age, sex, region, tools, and measurement methods). Among the studied factors, age and rearing region were identified as determinants of biometric trait variability. Specifically, a significant improvement was observed at 3 years of age in traits such as thorax girth, withers height, back length, body length, tail-set height, and croup height. Regional differences in traits such as neck length, chest width, and croup length highlight the influence of geographical conditions and management practices. Sex had no significant effect. Given the cross-sectional and phenotypic nature of this study, and the lack of genetic (pedigree) and performance (race record) data, direct application of these findings in breeding programs requires further genetic and performance-based studies.
Type of Study: Research |
Subject:
ژنتیک و اصلاح نژاد دام
Received: 2025/10/25 | Accepted: 2026/08/17
Received: 2025/10/25 | Accepted: 2026/08/17
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