[Biochemical indicators of nitrogen and energy metabolism in the plasma and blood of beef bulls during the grazing season].

Concentrations of total proteins, urea, total lipids in the blood plasma and glucose concentrations in the blood of beef bullocks were followed after their transition from winter feed rations to pasture, and in the subsequent grazing cycles within two years. Blood was taken by punctures from the vena jugularis from the same six bullocks all the time. In the 1st year of observation, blood sampling took place a week before the bullocks were moved to pasture, in the 2nd year of observation blood was taken twice in weekly intervals before pasture. During grazing, biological material was sampled in weekly intervals between 1st and 5th week (May--cycle I, June--cycle II), then in the tenth week (July--cycle III) and in the 14 week (August--pasture cycle IV). The concentrations of total proteins in the blood plasma of beef bullocks (Fig. 1) insignificantly increased after transition from indoor housing to pasture, this increase continued in the second year of observation for two weeks after transition to pasture, and in the first year of observation for four weeks with a break in the 2nd week. In the subsequent period, the concentrations of total proteins decreased to the values approaching the starting values. The concentrations of plasma urea in beef bullocks (Fig. 2) significantly increased in both years of observation after transition from stable fattening to pasture (p < 0.01 and p < 0.05, resp.). In the second week after transition to pasture, further highly significant increase in the concentrations of plasma urea was observed in both years of observation.(ABSTRACT TRUNCATED AT 250 WORDS)