KINETICS OF PLASMA FRUCTOSE AND GLUCOSE WHEN LACTOSE AND FRUCTOSE AREUSED AS ENERGY SUPPLEMENTS FOR NEONATAL CALVES

Shortly after birth, plasma glucose and fructose concentrations of the neonate decline and thus leave blood sugar below the homeostatic mode . Two trials mere conducted to determine the plasma glucose and fructo se kinetics in control and supplemented calves for 108 h after birth. In the shortterm trial, six Holstein calves were given 40 g of either fructose, lactose, or water (control) orally at 1 and 96 h after birth . Treatments were administered with a colostrum substitute (Life Boost (TM)) at 1 h and whole milk at 96 h. Rectal temperatures and changes i n plasma glucose and fructose concentrations were monitored at close i ntervals for 12 h after supplementation. In the long-term trial, 15 Ho lstein calves were given 40 g of either lactose, fructose, or water (c ontrol) at 1 h after birth and at 12-h intervals for 81 h. Plasma gluc ose and fructose concentrations were determined before and 4 h after e ach of the seven feedings. Early postpartal feeding of fructose suppre ssed plasma glucose (similar to 50%), with a reciprocal rise in plasma fructose. Irrespective of treatment, plasma glucose concentrations di d not stabilize (similar to 100 mg/dL) until 17 to 24 h after birth. A fter 24 h, lactose supplements increased concentrations of plasma gluc ose 4 h after supplementation (169.7 +/- 8.2 mg/dL), compared with tho se in calves that did not receive the additional lactose. After 24 h, fructose supplements did not affect plasma glucose, but plasma fructos e concentrations increased (82.6 +/- 12.4 mg/dL) 4 h after administrat ion. The response to fructose supplements declined by 11.4 mg.dL(-1).d (-1). Fructose was not detected in the plasma of control or lactose-tr eated calves after 17 h after birth. Calves that received fructose sup plements had rectal temperatures 8 and 10 h after birth that were high er than those of the other calves. The mechanisms of sugar metabolism change quickly following birth. Oral sugar supplements increase the to tal plasma sugar concentrations of treated calves.