99. Myth or Real? Measuring the rate of collagen degradation in the Friesian horse has little significance when trying to explain the predisposition of this breed to soft tissue diseases.

Answer: Myth
In a recently published paper, a group of researchers undertook a project to examine breed-related differences in the breakdown of collagen. Their interest in this stems from the thought that issues such as aortic rupture, megaesophagus and gastric rupture are ”a manifestation of a presumed underlying soft tissue disorder.” Specific components of collagen called cross-links bind adjacent collagen chains into a triple-helix type structure. This is important as when collagen is broken down/degraded, these cross-links are released into the bloodstream and excreted from the body in the urine. Two particular types of cross-links, abbreviated PYD (pyridinoline, a bone degradation marker and also found in type 1 collagen) and DPD (deoxypyridinoline, found more widely distributed in connective tissue) can be measured in the urine of a horse. This project looked at the urinary excretion of these two cross-links in 17 Warmblood horses and 17 Friesian horses. Their hypotheses was that there would be a breed-related difference in this breakdown of collagen and thus, a breed-related difference in the rate at which these two products would be found in the urine. The urine of these horses was randomly sampled once a day while either at home or at a referral facility where they were undergoing anesthesia for surgical procedures and the levels of PYD, DPD and Cr (creatinine) were measured. Their results found a higher ratio of PYD/DYD being excreted in the urine of Friesian horses as compared to Warmblood horses, leading them to conclude that this was due to an increased breakdown of collagen in the Friesian. They concluded that this increased collagen catabolism could “explain the predisposition of the Friesian horse breed to several soft tissue diseases”. Article: Saey, V. et. al. Elevated urinary excretion of free pyridinoline in Friesian horses
suggests a breed-specific increase in collagen degradation. BMC Veterinary Research (2018) 14:139. https://doi.org/10.1186/s1291-018-1454-8.

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