Early Changes in Plasma Insulin and Growth Hormone Levels after Feeding in Lambs and Adult Sheep

Abstract

When lambs 1-3 months of age ingested 250 or 500 m1 of milk by sucking vigorously from a teat, there was a rapid increase in their plasma insulin concentration to a maximum 5 min after starting to suck. At the same time plasma growth hormone (GH) levels declined rapidly. Changes of comparable magnitude were also seen when lambs drank milk diluted with water or vigorously ate chopped lucerne hay, when adult wether sheep ate dry feed rapidly, and when an adult wether fitted with an oesophageal fistula was 'sham-fed'. The changes were not seen when sheep, although offered food, did not eat. These responses were not closely related to changes in plasma glucose or ",-amino nitrogen concentrations and they evidently involve reflex nervous mechanisms.