Studies on T3-125I uptake by resin in Hariana and its F1 crosses in relation to different climatic conditions

Series of experimental trials were undertaken on the bull calves of Haryana and its three F1 crosses with Holstein Friesian, Brown Swiss and Jersey exposed to experimental temperatures of 17 deg C to 37 deg C at 5 deg C intervals. The blood was sampled under natural climatic conditions prevailing at the time of different trials, during a week maintenance at 18.5 deg C and 37 deg C with respect to their thyroid status. An attempt has been made to assess the validity of measurement of thyroid status as an index to reflect the climatic adaptability of the different experimental groups. For the assessment of the thyroid function, in vitro techniques of tri-iodothyronine-125I uptake by resin were used. Thyroid activity tended to decline on exposure to higher temperature as observed, after the first nine days of exposure to 37 deg C. Towards the end of three weeks however, the values exhibited recovery towards normal level, indicating the relative adaptability of the indigenous Haryana and its crosses with temperate breed. The physiological implications of these studies are discussed. (author)