Short-Term Regulation of Plasma IGF-I Concentration by Food Intake in Young Growing Pigs

Summary

The short-term regulation of plasma insulin-like growth factor-I (IGF-I) concentration by food intake has been studied in 6-8 week old pigs, both within the thermally neutral zone (26 to 30°C) and at a low (12°C) environmental temperature. In animals at thermal neutrality, the plasma level of IGF-I increased significantly after feeding (p<0.025 to <0.01); the average maximum rise of 47% occurred at approximately 12 h after the meal. When animals were acclimated to a low temperature and food intake was kept constant in relation to body weight, there was a decline in plasma IGF-I concentrations; values after 2-5 days of cold-acclimation were significantly lower than those before cold exposure (p<0.05 to <0.005). This effect of cold on plasma IGF-I was probably mediated by changes in energy balance, due to the increased metabolic demand associated with the low temperature. Animals living in the cold for 14 days, with a low fasting level of plasma IGF-I, showed a marked increase in IGF-I after a large meal; values at 8 or 12 h after food were twice as great as those immediately before or 4 h after feeding (p<0.05 to <0.005). It is concluded that in young growing animals, a rapid increase in circulating IGF-I levels can occur in response to food intake, at both thermally neutral and low temperatures, and that the peak in concentration may coincide with the anabolic effects of the meal.

Key words

Energy Balance - Food - Growth - IGF-I - Nutrition - Temperature