44 Detecting conformational differences in Fragile Foal Syndrome carriers utilizing artificial intelligence

Conformation traits impact gait and performance, and as a result vary based on intended use of the horse. For example, a horse with longer legs can cover a greater distance per stride than one with shorter legs. Limb length, therefore, is advantageous for horses expected to travel long distances for extended periods of time but may not be for those who go short distances at top speeds. Fragile Foal Syndrome (FFS) in horses results from a sequence change in PLOD1, the same gene that causes Ehlers Danlos Syndrome type IV (EDS-IV) in humans, a condition that results in longer limbs. Based on the phenotype observed in EDS, we hypothesize that FFS in the carrier state may impact extremity length including the neck, forelimbs, and hindlimbs in horses. To measure conformation parameters, we first digitally labeled specific anatomical points on a video recording of a trotting horse using the software package DeepLabCut (DLC). Representative frames for each horse at the same point within the stride were extracted from the video. The X, Y coordinates of each anatomical label were used to quantify conformation geometry. Frame extraction was done with a custom designed graphical interface that ensured the user could identify the ideal frame matching an identical body position across all horses examined. X,Y coordinate output files were thenanalyzed with a custom gait parameter pipeline written in MatLab to calculate the neck, forelimb, and hindlimb length. Each measurement was scaled to account for the varying distance horses were from the camera. Pulled tail hair was utilized to extract DNA and genotype each horse using PCR-RFLP, then followed by Sanger Sequencing for confirmation. Conformational measures were compared between genotype categories (wild type vs, carrier) in JMP Pro. Preliminary results showed that FFS carriers (n = 7) had significantly longer forelimb (P = 0.0344, t-test), hindlimb (P = 0.0258, t-test), and neck (P = 0.0013, t-test) lengths compared with wild type horses (n = 7). Future work will increase the overall sample size and number of frames captured per individual to increase statistical power and allow investigation of more conformation traits including static joint angles and back lengths. Improved understanding of conformational phenotypes that may result from the FFS carrier genotype will inform future studies of equine physiology and connective tissue disorders, leading to better decision making for breeding, sales and training, and prev