Metabolic and cellular profile testing in calves maintained under feedlot conditions: protein fractions and lactate dehydrogenase isoenzymes--changes over time.

Mean concentrations for total serum protein and serum protein fractions, and mean activities for total lactate dehydrogenase (LDH) and LDH isoenzymes were determined in 114 crossbred yearling cattle during a 56-day feeding trial. These values were to be used as predictors of performance (weight gain). The mean total serum protein concentration on day 0 was high (7.27 g/dl), reached a low on days 7 and 14 (6.47 and 6.50 g/dl), and then equilibrated toward the end of the study. The mean concentration for the albumin fraction also reached a low on days 7 and 14 (2.83 and 2.84 g/dl) and then increased, remaining steady until termination of the feeding trial. The alpha-, beta-, and gamma-globulin fractions fluctuated throughout the study. The mean for total LDH activity peaked on day 21 (1,363 IU) and then remained relatively constant through day 56. Mean serum activities for the LDH3 activity peaked on day 7 (27%) and then decreased progressively to day 56 (17%). The overall trend for LDH4 and LDH5 activities seemed to be a steady increase.