Dynamic Change of Free Serum L-carnitine Concentration in Relation to Age, Sex, and Exercise in Anglo-Arabian Thoroughbred Horses

The physiological role of L-carnitine in equine species is worthy of investigation; however, the systemic content of free L-carnitine and its dynamic change in growing foals as well as in exercising horses are still poorly investigated. In this study, the influence of age and exercise on free serum L-carnitine levels was evaluated in equine species. Ten foals were monitored from 6 up to 18 months of age (group 1), whereas 60 horses were divided in six groups in accordance with their age: group 2, 2-year-old; group 3, 3-year-old; group 4, 4-year-old; group 5, 5-year-old; group 6, 6-year-old; group 7, 7-year-old. To assess the age and sex effect on free serum L-carnitine values, blood samples were collected from foals and horses. Adult horses (groups 2–7) were subjected to a simulate 1,660-m race, and blood samples were collected before the simulate race (TPRE), within 10 minutes (TPOST10) from the end of race, and after 30 minutes (TPOST30) from the end of race. The amino acid levels were influenced by age (P <.0001) in foals and horses. Decreased levels of amino acid were observed at TPOST10 with respect to TPRE and TPOST30. (P <.001). The findings suggest that the biosynthetic pathway of L-carnitine is organizing and adapting to the metabolic needs of skeletal and cardiac muscle tissue in the course of growth. L-carnitine could play a role for the provision of energy to the exercising muscles. Further studies are needed to evaluate possible beneficial effects of L-carnitine during growing phase and on parameters of equine physical performance