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Some Biochemical Parameters of Nitrogen and Energy-Metabolism in the Plasma and Blood of Beef Bullocks in the Grazing Season

ZITNAN R, GALLO J, GALLO M, BOMBA A, SOMMER A
Veterinarni Medicina 38, 1993, 521-529

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. In the subsequent period of grazing, urea concentrations in the blood plasma decreased to the values slightly higher than the starting values. Glucose concentrations in the blood of fattened bullocks (Fig. 3) decreased significantly after transition from stable fattening to pasture (p < 0.01), and highly significantly in the second year of observation (p < 0.001). Glycemia was increasing from the fourth week after transition to pasture in both years, while this increase was significant in the first year of observation (p < 0.01). The concentrations of total lipids in the blood plasma of beef bullocks decreased only slightly after transition from stable fattening to pasture (Fig. 4), but this decrease continued in the second week of the second year of observation and was statistically significant (p < 0.05). In the subsequent grazing season the variations of total lipid concentrations were minimum. The average daily weight gain of beef bullocks in the grazing season was 0.530 kg in the first year of observation, and 0.470 kg in the second year


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