Prevalence of Chronic Progressive Lymphedema in the Rhenish German Draught Horse

SIMPLE SUMMARY: Chronic progressive lymphedema is a debilitating disease reported in several draught horse breeds. In this study, we analysed the prevalence of this condition and its progression with age in males, geldings, and females in Rhenish German draught horses. In addition, we recorded horse farm-related factors and evaluated their effects on chronic progressive lymphedema. All horses less than 1 year old were not affected by this disease. The first cases were seen in horses that were 1–2 years old. The prevalence of more severe cases increased with an age of 3–6 years. Males were at a 5-fold higher risk for chronic progressive lymphedema than females. Progression with age was faster in males than in females and geldings. Disease progression stopped at a mean age of 16 years in males, 18 years in geldings, and 20 years in females. We found distinct differences among the prevalence of chronic progressive lymphedema among breeding associations. Horses kept on pastures had lower disease scores. Horses with rations in winter without concentrates and rations without hay silage exhibited lower scores for chronic progressive lymphedema. Cannon bone circumference correlated with disease scores, while hoof measures and skinfold diameter at the neck did not. Reducing farm-related risk factors should help to reduce the progression of chronic progressive lymphedema in Rhenish German draught horses. ABSTRACT: Chronic progressive lymphedema (CPL) is a common disease in Rhenisch German draught horses. The objective of our study was to evaluate the prevalence of this disease and its progression with age in 493 Rhenish German draught horses from different regions in Germany. We employed generalized linear models with binomial, multinomial, and normal distributions to analyse the effects of breeding association, coat colour, sex and age within sex, time of examination, limb on which CPL was recorded, and farm-related factors on disease scores. The occurrence and severity of CPL were significantly influenced by breeding area, sex, coat colour, and interaction of age by sex. Males had significantly higher CPL-scores than geldings (1.92-fold) and females (5.02-fold) as well as a faster (1.85-fold) disease progression per year of life than females (1.44-fold) and geldings (1.25-fold). Regression on age within sex was still significant when age was restricted to a minimum of 7 years in the analysis. Bay horses exhibited 1.77-fold and 2.19-fold higher CPL-scores than chestnut and black horses. Keeping horses on pasture and keeping bedding clean reduced CPL-scores, whereas feeding of hay silage and concentrates during winter increased CPL-scores. Our analysis revealed significant regression coefficients of cannon bone circumference on CPL-scores. Relationships with hoof measures and skinfold diameter at the neck were not found. In conclusion, differences among breeding districts and sexes by age had the largest impact on CPL prevalence and scores. Disease progression was evident up to a mean age of 16 years in males and 20 years in females. The identification of risk factors and their effects on CPL should help to reduce the occurrence and progression of CPL.