Response of Plasma Glucagon-Like Peptide 1 Concentration to Oral Administration of Lactose and Casein in Preweaning Calves.

This study investigated the effects of orally administered sugars and casein, main components of whole milk, on plasma glucagon-like peptide 1 (GLP-1) concentration in preweaning calves. In Experiment 1, calves received water (CON), 2.37% (w/w) glucose (GLU), 2.37% galactose (GAL), or a mixed solution containing 2.37% each of glucose and galactose (GLU + GAL). In Experiment 2, calves received 4.5% (w/w) lactose (LAC), 3.0% casein (CAS), or a mixed solution containing lactose at 4.5% and casein at 3.0% (LAC + CAS). Because baseline plasma GLP-1 and α-amino nitrogen (AAN) concentrations varied greatly and correlated with postadministration mean concentrations, statistical analyses for these parameters included baseline values as covariates. In Experiment 1, glucose and insulin concentrations were higher in GLU and GLU + GAL than in CON (p < 0.001), whereas GLP-1 concentrations were lower in GAL than in other groups (p < 0.001). In Experiment 2, glucose and insulin concentrations were higher in LAC and LAC + CAS, AAN concentrations were higher in CAS and LAC + CAS, and GLP-1 concentrations were higher in LAC, CAS, and LAC + CAS compared with CON (p < 0.001). In conclusion, both lactose and casein promoted GLP-1 secretion in calves, although oral administration of glucose or galactose alone did not elicit a marked GLP-1 response.