Correlations between body dimensions of young trotters and motion parameters and racing performance

Body measurement of riding horses with a versatile tablet-type 3D scanning device

The measurement of various body dimensions of horses plays a significant role in quality improvement, genetic breeding, health, and soundness. There has been significant advancement in the technology for acquiring stereoscopic images with a three-dimensional (3D) scanner. This study aimed to validate the accuracy of body measurements obtained from stereoscopic images taken with a 3D scanner. We manually took the following body measurements for 8 riding horses: height at the withers, height at the back, height at the croup, chest depth, width of the chest, width of the croup, width of the waist, girth circumference, cannon circumference, and body length. Using a versatile tablet-type 3D scanning device, we captured a 3D image of each horse. Relative errors varied from −1.37% to 6.25%. The correlation coefficient between manual and 3D measurements was significant for all body measurements (P<0.01) except for width of the waist and cannon circumference. The low accuracy of cannon circumference (r=0.248) was due to effect of hair. A simple regression analysis of all body measurements revealed a strong correlation (P<0.001, R²=0.9994, root-mean-square error [RMSE]=1.522). Notable advantages of this methodology include high accuracy, good operability, non-contact, high versatility, and low cost. Further studies are required for the establishment of an accurate measurement methodology that can scan the whole body in a shorter time.

A QTL for conformation of back and croup influences lateral gait quality in Icelandic horses

BACKGROUND

The back plays a vital role in horse locomotion, where the spine functions as a spring during the stride cycle. A complex interaction between the spine and the muscles of the back contribute to locomotion soundness, gait ability, and performance of riding and racehorses. Conformation is commonly used to select horses for breeding and performance in multiple horse breeds, where the back and croup conformation plays a significant role. The conformation of back and croup plays an important role on riding ability in Icelandic horses. However, the genes behind this trait are still unknown. Therefore, the aim of this study was to identify genomic regions associated with conformation of back and croup in Icelandic horses and to investigate their effects on riding ability. One hundred seventy-seven assessed Icelandic horses were included in the study. A genome-wide association analysis was performed using the 670 K+ Axiom Equine Genotyping Array, and the effects of different haplotypes in the top associated region were estimated for riding ability and additional conformation traits assessed during breeding field tests.

RESULTS

A suggestive quantitative trait loci (QTL) for the score of back and croup was detected on Equus caballus (ECA) 22 (p-value = 2.67 × 10- 7). Haplotype analysis revealed two opposite haplotypes, which resulted in higher and lower scores of the back and croup, respectively (p-value < 0.001). Horses with the favorable haplotype were more inclined to have a well-balanced backline with an uphill conformation and had, on average, higher scores for the lateral gaits tölt (p-value = 0.02) and pace (p-value = 0.004). This genomic region harbors three genes: C20orf85, ANKRD60 and LOC100056167. ANKRD60 is associated with body height in humans. C20orf85 and ANKRD60 are potentially linked to adolescent idiopathic scoliosis in humans.

CONCLUSIONS

Our results show that the detected QTL for conformation of back and croup is of importance for quality of lateral gaits in Icelandic horses. These findings could result in a genetic test to aid in the selection of breeding horses, thus they are of major interest for horse breeders. The results may also offer a gateway to comparative functional genomics by potentially linking both motor laterality and back inclination in horses with scoliosis in humans.

An Accurate Image Analysis Method for Estimating Body Measurements in Horses

This study proposes a standardized image analysis method for assessing horse conformation. A total of 34 adult American Quarter Horses (mean age = 6.7 ± 2.9 years, body weight = 489 ± 44 kg) were used. Reference angular measurements were performed using a digital goniometer, and reference linear measurements were determined using a standard measuring tape. For image analysis, photographs from the animal's left profile were taken at a distance of 3 m using eight markers to facilitate visualization. Images were processed using ImageJ software. Reference and estimated values showed great accuracy, with v² < 1%, Pearson's correlation coefficient > 0.999 (P < .001), and coefficient of variation < 2.70. Image analysis and reference results were similar (P > .05) for most variables. The highest coefficient of variation (3.05%) was observed for coxae-femur angle, where the software obtained an underestimation of 2.8° compared with the reference method. Body length resulted in an overestimation of 3.4 cm in relation to reference values, but coefficient of variation was low (1.54%). Discrepancies between estimated and reference results can be attributed to possible errors when collecting biometric data using portable measuring tools, angles and long measurements being more difficult to obtain. Software analysis of standardized horse photographs is an accurate and precise method for obtaining body measurements and is therefore recommended for future studies on horse conformation.