Effects of Monensin on Postprandial Changes in Concentrations of Blood Plasma Free Amino Acids, Urea, Insulin and Glucose of Steers

Abstract

Effects of monensin on postprandial changes of blood plasma metabolites were studied using 4 steers by a switchback trial with 3 weeks of each period. The steers were fed 2kg of concentrate and 10kg of grass silage twice daily. Steers in monensin-fed group were given a concentrate supplied with 40ppm monensin. On the last day of each period, blood samples were collected with test tube containing heparin for the determinations of blood plasma metabolites at 0, 1, 2, 4 and 6hr after the start of feeding. 1) Ht values in the monensin-fed group were generally higher than those in the control one. Feed intake decreased Ht values in both groups. 2) Plasma urea nitrogen was higher in the monensin-fed group than that in the control group. Feed intake increased it in all steers. 3) Plasma glucose concentrations reached maxima at 4hr after feeding in both groups. The adding of monensin produced no alteration in plasma glucose concentration. 4) The highest value of plasma insulin concentration was found at 1-2hr after the start of feeding in both groups. The elevated concentrations were maintained until 6hr after the feeding. Its concentration during 2-6hr was higher in the monensin-fed group than that in the control one. There was no evidence that the increases in insulin after feeding resulted from increases in plasma glucose. 5) Plasma free amino acids (FAA), essential amino acids (EAA) and non-essential amino acids (NEAA) concentrations decreased in all steers after feeding. Though there was no difference in FAA concentration between two groups, EAA concentration in the monensin-fed group was lower than in the control one. As the results, the ratio of EAA to NEAA was lower in the monensin-fed group than in the control one