[The effect of a light regimen on the dynamics of biochemical indicators in the blood, serum and urine of heifers during 1 day].

: Circadian dynamics of 38 biochemical parameters of the blood, serum and urine of heifers was studied under the natural light conditions of a light (160-180 lux) and dark (10-40 lux) small cow house. In each house, eight parameters were subject to a significant influence during the day, six of them being the same in both houses: calcium, chlorides, urea and thyroxine of blood serum, glucose and haematocrit in the blood of heifers. The comparison of parameters in different groups showed that different light regimes exerted a significant influence on calcium, chlorides, total protein, cholesterol, vitamin A and thyroxine in serum, haematocrit and leucocyte count in blood, and sodium and urea in the urine of heifers. The effect of feeding regime on the dynamics of parameters was tested by the calculation of the percentual fluctuation of their average values in heifer blood and serum before feeding (samples taken at 6.30 hrs) and after feeding (sampled at 10 hrs). In the light house, six parameters were judged to be less stable and one unstable (urea in serum). In the dark house six parameters were less stable and four unstable (calcium, urea, copper and thyroxine in serum).