Plasma insulin levels in weaned pigs fed protein or energy restricted diets

Two experiments were conducted with pigs to investigate changes in plasma insulin levels during protein-energy malnutrition. Three or four week old pigs were fed a control diet (18% protein), an energy-restricted diet (19% protein) or a low protein diet (6% protein) for 8 weeks. Energy restriction was achieved by feeding the control diet in amounts that allowed some growth, but only to an extent equal to the low protein diet. At the end of the restriction period, all pigs were fed the control diet for another 8 weeks. Blood samples from the superior vena cava were collected at intervals throughout the experimental period. Plasma samples were analyzed for insulin by radioimmunoassay. Protein restriction after weaning resulted in persistently low insulin levels during depletion and rehabilitation periods, while high levels of plasma insulin were observed in energy-restricted pigs only during the depletion period compared to pigs fed the control diet.