[The effect of extreme temperatures on hematologic and biochemical indicators in heifers].

The study was aimed at finding the effect of low and high temperatures on some biochemical parameters in heifers. Thirty half-sister heifers were used as the experimental material. The animals were divided into two groups. The experimental group including 16 heifers was kept loose on deep litter in an open barn with no thermal insulation. The control heifers (n = 14) were kept in a thermally insulated house. Blood was collected at extreme temperatures: above 30 degrees C and below -5 degrees C. An insignificant decrease of haemoglobin and haematocrit was recorded in the blood collected at low and high temperatures from the heifers kept in the open barn; a reduction of cholesterolaemia and total lipaemia was recorded at high temperatures. High and low temperatures significantly increased the concentration of free amino acids; the differences between the experimental and control group being from 36 to 76 mumol per litre. The content of 3.5-cyclic adenosine monophosphate was increased insignificantly at extreme temperatures. Hyperglycaemia was recorded in the heifers at high temperatures and at the beginning of the winter season. At low temperatures the concentration of thyroxine was found to be increased in the blood of the experimental animals: 120 nmol per litre and 161 nmol per litre vs. 95 nmol and 116 nmol in the control group.