Thyroid hormones have been recognized to be important in establishing the animal performance as, growth, maturation, reproduction, production and adaptation. The aim of this work was the estimation of triiodothyronine (Tӡ) and parathermon (PTH) hormones concentrations and their relations with some serum biochemical levels in buffalo calves. A total number of 50 male buffalo calves divided into two groups according to their age, 20 animals (3 to 6 months age) and the other 30 ones (6-9 months

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... ). These animals were apparently healthy male buffalo calves selected from a privet farms at Assiut governorate. Blood serum sample were used for determination of triiodothyronine (Tӡ) and parathermon (PTH) hormones concentrations and the total protein, albumin, globulin, glucose, cholesterol, calcium, phosphorus, and magnesium levels. The results indicated a significant decrease of both blood serum hormones (Triiodothyronine (Tӡ) and Parathermone (PTH) concentrations in the older age group of buffalo calves were collected. There were a significant difference between the two age groups in both cholesterol and glucose levels. The mean values of calcium and magnesium showed significant difference between the two age groups. The correlation coefficient (r) between the estimated blood serum Triiodothyronine (Tӡ) concentrations and the different biochemical parameters only showed significant changes for glucose and cholesterol levels. Also, there was negative correlation only between parathermone (PTH) and, calcium, phosphorus, magnesium levels. Based on the current study, it could be concluded that the recorded biochemical parameters found to be lower than that recorded by other studies and this may attributed to many factors. The nutritional factor could be controlled for buffalo calves in Assuit province by giving balanced ration to improve such parameters and consequently improving animal performance.