PLASMA CONCENTRATION OF L. THYROXINE (T₄). L. TRIIODOTHYRONINE (T₃) AND CERTAIN OTHER BLOOD BIOCHEMICAL CONSTITUENTS IN GROWING CROSSBRED (B0S taurus × B0S indicus) CALVES

The relationship of thyroid status and certain blood biochemical constituents with body weight gains (ADG) and age (13 to 96 weeks) was studied in Holstein Friesian ${\times}$ Hariana ($1/2F{\times}1/2H$) crossbred male calves by assessing their plasma triiodo thyronine ($T_3$), Thyroxine ($T_4$), sodium, potassium, total proteins and cholesterol level at two energy levels. Body weight gains (ADG) were higher during the 50 to 72 weeks of age and declined thereafter, the plasma $T_3$ conc. was aignificantly (p < 0.01) higher during this period compared to all other periods. There was no significant variation due to energy level. Overall mean plasma $T_3$ conc. was $1.19{\pm}0.12ng/ml$. Plasma $T_4$ conc. did not show any significant variation either between the different age periods or between the two energy levels. The mean plasma $T_4$ conc. was $37.34{\pm}1.32ng/ml$. The plasma sodium and potassium concentration did not vary significantly due to energy levels. But amongst the different age periods, sodium concentration was highest ($147.70{\pm}2.29mEq/L$) during 49-60 weeks of age and lowest ($134.70{\pm}1.78mEq/L$) during 13-24 weeks, where as for potassium concentration changes were nonsignificant. There was very little variation amongst other periods. Plasma protein level was higher at 100% energy level than at 75%. Amongst the different age period, it was significantly lower ($6.44{\pm}0.36$) during 13 to 24 weeks of age than at 37 to 48 weeks of age ($7.14{\pm}0.11$). Plasma cholesterol values were higher for 75% energy level than that of 100%. Between the periods it was highest during 61 to 72 weeks of age and the difference amongst the age period were highly significant.