Serum and urine concentrations of protein, urea, sodium, and potassium during the immediate postnatal period of the suckling pig.

Serum and urine concentrations of protein, urea, Na and K were monitored between birth and 72 h in neonatal pigs. Serum protein increased (p less than 0.05) 37 mg/ml after suckling, while urinary protein temporarily increased (p less than 0.05) to 14.7 +/- 0.98 mg/ml by 12 h but declined (p less than 0.05) to birth values by 72 h. Urinary urea levels tripled (p less than 0.05) by 12 h and remained elevated. The ratio of urea of urea in the urine to that in the serum ranged from 17 to 29. Serum Na concentrations were stable (141--146 mEq/l) during the 72 h, and urinary Na levels were low (9--4 mEq/l) and decreased (p less than 0.05) by 72 h. Serum K fluctuated and was highest (p less than 0.05) at birth (6.4 +/- 0.26 mEq/l) and lowest by 72 h (4.4 +/- 0.26 mEq/l). Levels of K excreted in the urine were high (20.0--7.6 mEq/l) compared to blood levels. Colostral concentrations of Na were low (81--73 +/- 3.8 mEq/l) while K levels were high (24.3--28.8 +/- 1.39 mEq/l) compared to piglet serum levels.