Response of Plasma Glucagon-Like Peptide 1 Concentration to Oral Administration of Lactose and Casein in Preweaning Calves.
GLP-1 isn’t just a human story. Researchers in Japan just showed that both lactose and casein—core parts of milk—spark a clear rise in plasma glucagon-like peptide 1 (GLP-1) in preweaning calves. This is a solid reminder that peptide signaling and nutrient sensing are tightly linked, even in young livestock.
Anim Sci J
by Inabu Y, Satoh M, Obitsu T et al.
“Response of Plasma Glucagon-Like Peptide 1 Concentration to Oral Administration of Lactose and Casein in Preweaning Calves. Inabu Y(1), Satoh M(2), Obitsu T(1), Sugino T(1). Author information: (1)Graduate School of Integrated Sciences for Life, Hiroshima University, Higashihiroshima-shi, Hiroshima, Japan. (2)School of Applied Biological Science, Hiroshima University, Higashihiroshima-shi, Hiroshima, Japan. 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. © 2026 The Author(s). Animal Science Journal published by John Wiley & Sons Australia, Ltd on behalf of Japanese Society of Animal Science.”
The team ran two experiments. First, they gave calves water, glucose, galactose, or a glucose-galactose mix. Only the glucose groups ramped up blood glucose and insulin, but galactose actually dropped GLP-1 levels. Second round: calves got lactose, casein, or both. Here’s where it gets interesting—lactose and casein (alone or combined) all boosted GLP-1 compared to water.
Key takeaway: just dumping in glucose or galactose doesn’t do much for GLP-1. But give calves lactose or casein, and the gut lights up. This matters for anyone studying nutrient-driven peptide release—not just in animals, but for broader models of digestion and metabolism. If you’re tracking gut peptides, these results should be on your radar.
Other findings:
Glucose and insulin spiked with glucose and glucose+galactose, but not with galactose alone.
Amino nitrogen levels shot up with casein, confirming protein breakdown and absorption.
Baseline GLP-1 levels varied between calves—future research should factor in this individual variation.
For researchers mapping out peptide pathways, these results add new fuel. Digging into how different nutrients shape peptide release in early life could open doors for both animal science and translational models. For more on current peptide work, check our peptide research index.
Bottom line: what you feed matters for peptide signaling, even before weaning.
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