Most producers think of colostrum as a day-one job, get it in fast and move on. This study looked at what happens when colostrum feeding gets extended out to three days postnatal instead of stopping after the first feeding, specifically tracking a hormone called GLP-1 that's tied to how a calf regulates blood sugar and insulin. Calves that kept getting colostrum through day three showed higher GLP-1 levels than those switched to milk, suggesting there's a metabolic benefit to sticking with colostrum longer than the bare minimum.
"Effect of extended colostrum feeding on plasma glucagon-like peptide-1 concentration in newborn calves" — Y. Inabu, J. Pyo, S. Pletts, L.L. Guan, M.A. Steele, T. Sugino. J Dairy Sci. 2019;102(5):4619-4627.