Student University of Arizona Chandler, AZ, United States
Abstract:
Objective: This project aimed to establish reference intervals for key metabolic biochemical measurements and assess the prevalence and impact of risk factors for metabolic syndrome in mules. Animals: 159 mules and 31 horses (2-20 years old)
Methods: Phenotypic data included fasting insulin, triglycerides, ACTH, non-esterified fatty acids (NEFA), and insulin post oral sugar test (INS-OST), body condition score (BCS), and cresty neck score (CNS). Stepwise regression was used for model analysis with farm as a random effect and sex, age, CNS, BCS, and month as fixed effects. The percentage of phenotypic variation explained by each predictor was calculated from mixed model analyses. Significant differences between horses and mules were identified using pairwise comparisons with a Tukey-corrected p-value < 0.05. Parametric reference intervals were calculated using data from 117 mules (2-15 years old, BCS 4.5-7), applying Cook's distance for outlier detection.
Results: Across our cohort, 15% of the mules were obese and 32% had a CNS ≥3. CNS and sex significantly influenced most outcome variables, explaining 1-5% of the variation (R2), while farm accounted for 18-26%. Triglycerides were 1.4 times higher (: 95% CI 1.08-1.59, p=0.007) and ACTH 1.3 times lower (95% CI 1.08-1.49, p=0.003) in mules than horses. Mule-specific reference intervals were established for ACTH (2.6-22.2 pg/mL; p< 0.001), insulin (2.6-18.0 µIU/mL; p< 0.001), triglycerides (11.6-98.6 mg/dL; p=0.02), NEFA (≤0.44 mmol/L; p< 0.001), and INS-OST (2.5-27.9 µIU/mL; p< 0.001). Conclusion and Clinical Importance: These results provide essential insights into the metabolic health of mules and provides initial information to diagnose metabolic changes in mules.
