Relationship of Carnitine and Acylcarnitines in Ejaculated Sperm to Blood Plasma Testosterone of Dairy Bulls1

Blood plasma testosterone concentrations were significantly negatively correlated (r = −0.91, P<0.05) with blood plasma carnitine concentrations among dairy bulls of varying fertility levels. Blood plasma testosterone was positively correlated with spermatozoa total carnitine (r = 0.32), spermatozoa acylcarnitines (r = 0.35), and sperm motility (r = 0.49), whereas blood plasma carnitine concentration was negatively correlated with spermatozoa acylcarnitines (r = −0.48), spermatozoa total carnitine (r = −0.36), and sperm motility (r = −0.39). Furthermore, the concentrations of total carnitine (r = 0.67), free carnitine (r = 0.75), and acylcarnitines (r = 0.60) of spermatozoa were positively correlated with sperm motility ratings. Bulls exhibiting the highest fertility levels also had the higher concentration of blood plasma testosterone and lower concentration of blood plasma carnitine. Although several correlation coefficients are not statistically significant, they compare favorably with published values and support the biological importance of these blood plasma constituents as they are related to spermatozoa carnitines and their function in maintaining sperm motility and thus fertility.