Insulin and glucose in neonatal calves after peroral insulin and intravenous glucose administration

Effects of peroral insulin on plasma concentrations of immunoreactive insulin (IRI) and glucose in newborn calves were studied. Bovine insulin was administered in amounts of 0.5 mg/kg body weight immediately preceding first colostrum. Thereafter, neither an increased IRI response nor a lowering of blood glucose level were observed, indicating that insulin was either not absorbed from the intestine or possibly retained in the liver. Feeding of whole milk was followed by a higher rise in IRI and glucose concentrations than feeding of colostrum after po insulin. However, when compared with 1-3-month old calves, IRI responses to feeding and to iv infused glucose were markedly smaller on the first and second day of life respectively, while glucose responses were similar. This indicates that insulin secretory mechanisms are not fully developed in the newborn calf.