Effect of Age on the Inflammatory Response in Horses Following an Incremental Exercise Test

December 2022
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Horses experience systemic and external inflammation following exercise as a mechanism of recovery indicated by elevated inflammatory markers and heat. Further, aged horses are at greater risk of prolonged inflammation than young horses. Therefore, the objective of this study was to compare the inflammatory response of unconditioned young (YNG; 14 to 16 mo) and aged (OLD; 19 to 24 yr) Quarter Horses following a 17-min incremental exercise test (IET; 6.44 kph, 16.09 kph, 19.31 kph and 22.53 kph). Blood was collected pre-exercise, 12 h, 24 h, 48 h, and 72 h following exercise. Skin surface temperatures were collected on the left side pre-exercise, 15 min, 24 h, 48 h, and 72 h following exercise. Muscle soreness evaluations were conducted pre-exercise, 12 h, 36 h, 60 h, and 84 h following exercise. Data were analyzed by repeated measures ANOVA using the MIXED procedure of SAS. Plasma percentages of 18:2 were greater in YNG 24 h following exercise than OLD (P<0.05). Plasma percentages of 18:3 and 22:6 were greater (P<0.05) prior to exercise than following exercise. There was an effect of age, where plasma IL-1β concentrations, mRNA abundance of IL-1β, and mRNA abundance of IL-18 in OLD were greater (P<0.05) than YNG. There was an effect of exercise, where mRNA abundance of IL-18 and caspase-1 were greater (P<0.05) 24 h following exercise than prior to exercise. Aged horses had greater (P<0.05) muscle damage 12 h following exercise compared to prior to exercise. The shoulder, forearm, back, and gaskin skin surface temperatures were greater (P<0.05) 15 min following exercise. All four muscle groups on the right side had a greater (P<0.05) muscle soreness score 12 to 60 h following exercise, while only the neck and shoulder on the left side exhibited muscle soreness in response to exercise (P<0.05). These results indicate that the response to an IET is affected by age in regard to plasma lipid content, plasma IL-1β concentrations, plasma CK concentrations, and gene expression of IL-1β, while age and exercise affect expression of IL-18. Additionally, these results suggest that exercise affects body surface temperatures and muscle soreness, regardless of age.

Agriculture, Animal Culture and Nutrition, Biology, Animal Physiology