Cortisol levels after low-dosage dexamethasone treatment in cattle

In a preliminary study (Capolongo et al., 2007) the reduced urine excretion of cortisol (F) and 6beta-hydroxycortisol (6betaOHF) in cattle treated per os with low doses of dexamethasone (DEX) was proved. To confirm the previous data, 16 male cattle were divided into two groups: a control group (K - 8 animals) and a DES-treated group (T - 8 animals), administered with unifeed spiked with DEX 0.75 mg/head, daily for 43 consecutive days. Urine and blood samples were collected from all the animals at day 19th and 43th during treatment and at day 45th, the slaughter-time of 12 animals. In treated animals, plasma F content was always below the limit of quantification of the Immunolite test used. Determination of F by RIA and of 6betaOHF by ELISA confirmed a statistically significant decrease in urine excretion from treated vs control animals (p<0.01 at T19 and p<0.001 at T43 and T45 for F; and p<0.05 at T19 and p<0.001 at T43 and T45 for 6betaOHF). The decrease of both analytes was maintained also in urine of the two further animals slaughtered at day 47. The quali-quantitative analysis of the same samples were repeated by an LC-MS/MS method, developed for the detection of corticosteroids in urine. The results revealed the reduced excretion of cortisone further to that of F, 6betaOHF in treated vs control animals. This project was supported by: University of Padua (CPDA077393)