Thyroid hormones response to marcha gait in Mangalarga Marchador horses* Resposta dos hormônios da tireoide após a execução da marcha em equinos da raça Mangalarga Marchador

The aim of this study was to evaluate thyroid hormones response to marcha gait by measuring serum concentrations of total (TT4) and free thyroxine (FT4), and total triiodothyronine (TT3) in Mangalarga Marchador horses. Blood samples were collected from 15 Mangalarga Marchador horses at four different moments: before (M0) and within five minutes (M1), 30 minutes (M2) and 2 hours (M3) after exercise (marcha gait for 40 minutes). Mean values of TT4 were 2.24 ± 0.36 µg/dL on M0, 2.41 ± 0.35 µg/dL on M1, 2.76 ± 1.36 µg/dL on M2 and 2.36 ± 0.40 µg/dL on M3 (p=0.2906). Mean values of FT4 were 0.78 ± 0.14 ng/dL on M0, 0.84 ± 0.11 ng/dL on M1, 0.89 ± 0.18 ng/dL on M2 and 0.85 ± 0.14 ng/dL on M3 (p=0.2305). For TT3, mean values were 0.92±0.28ng/mL on M0, 0.99±0.39ng/mL on M1, 1.20±1.07ng/mL on M2 and 0.87±0.24ng/mL on M3 (p=0.4697). Analysis of the results revealed that marcha gait did not influence serum mean values of thyroid hormones, although it was observed influence over heart rate and body temperature.