Plasma Concentrations of Hormones and Metabolic Substrates in Growing Pigs after Bovine Growth Hormone Injections under Various Nutritional Conditions

Abstract

The effects of GH injections on the concentrations of plasma hormones and metabolic substrates in pigs were studied under various nutritional conditions. In experiment 1, four pigs (Large white, barrows, 108 days old) were maintained at three feeding levels: (1) high level (8, 501±46kcal/day), (2) maintenance level (2, 104±44kcal/day), and (3) fasting (last meal was on day -2). The bovine GH (100μg/kg BW) was subcutaneously injected on experiment days 0, 1, and 2. In experiment 2, four pigs (Landrase, barrows, 120 days old) were maintained at the high feeding level and the bovine GH (100μg/kg BW) was injected 2, 26, and 50h after the last meal. The plasma hormone and metabolic substrate concentrations were measured. In experiment 1, the plasma IGF-I concentrations increased on days 1-4 in the high feeding level and maintenance fed pigs, but did not increase in the fasting pigs. The plasma glucose concentrations increased after the GH injection in the high feeding level and maintenance fed animals. The plasma NEFA concentrations increased after the GH injection in the maintenance fed and fasting animals. In experiment 2, the plasma IGF-I gradually decreased after the last meal. The GH injection administered 26 or 50h after the last meal still produced an increase in the plasma IGF-I levels. These data clearly show that the effect of GH was modified depending on the nutritional condition of the pigs.