Comparative appraisal of serum thyroid hormones in buffalo and cow bulls

Twenty two breeding bulls, comprising Murrah 4, Surti 5, Holstein Friesian 4, Jersey 4 and Crossbred bulls 5 (Holstein Friesian x Gir, and Jersey x Gir, with 50 to 75% exotic inheritance), maintained at Unit No. 16, Development Corporation of Konkan Limited, Aarey Milk Colony, Goregaon, Mumbai, were utilized for the present study. The animals were maintained throughout the experimental period under uniform plane of nutrition and management. Blood samples (10 – 15 ml) were collected by jugular venipuncture from each bull, at fortnight’s interval for 7 occasions, during the experimental period. The clear serum was separated by centrifugation and stored at -20 °C until used for Radioimmunoassay. The overall mean serum thyroidal hormones concentration obtained were: triiodothyronine 1.04±0.27, 1.34±0.15, 1.20±0.12, 1.17±0.11, 0.95±0.10 çg/ml; thyroxine 46.19±1.76, 53.03±1.26, 67.82±4.10, 70.00±3.56, 50.31±2.18 çg/ml; T₄:T₃ ratio 57.36±9.53, 41.34±4.70, 58.87±5.50, 61.40±3.65, 55.44±4.34 and TSH 0.083±0.01, 0.057±0.01, 0.109±0.01, 0.139±0.00, 0.143± 0.01 ìIU/ml in Murrah, Surti, Holstein Friesian, Jersey and crossbred bulls, respectively. The results revealed that serum triiodothyronine and the ratio of T₄:T₃, did not significantly differ and remained almost similar in buffalo and cow bulls. The serum thyroxine concentration was significantly higher in cow bulls than in buffalo bulls except in crossbreds, which was almost comparable with buffalo bulls. The mean serum TSH concentration was significantly higher in cow bulls than in buffalo bulls except in Holstein Friesian which did not significantly differ when compared with Murrah buffalo bulls. In buffalo bulls, the levels of TSH did not significantly differ.