Plasma insulin-like growth factor-I response to cold exposure in barrows

Information about the plasma IGF-I concentrations in domestic animals in a cold environment is still limited. And mechanisms to change plasma IGF-I concentrations in cold environments are not fully elucidated. In this study, plasma insulin-like growth factor-I (IGF-I) in relation to plasma growth hormone (GH) and metabolite concentrations was investigated in pigs living at 20 degrees C and at 4 degrees C. Six pigs (Landrase breed; barrows, 118 days old, 51.0 +/- 3.5 kg body weight) were maintained for 2 weeks at 20 degrees C in a climatic room. Then a placebo or recombinant bovine GH (100 micrograms/kg body weight) was injected subcutaneously. Blood samples were taken through a catheter at -2, 0, 1, 2, 3, 4, 5, 6, 9, 12, 22, and 24 h after the injections. The same experiments were conducted on days 5 and 6 after the room temperature was changed to 4 degrees C. Mean (+/- SD) basal plasma GH concentrations in pigs without bovine GH administration living at 20 degrees C and at 4 degrees C were 4.8 +/- 1.7 ng/ml and 4.6 +/- 2.8 ng/ml, respectively. There were no significant differences between GH concentrations. On the other hand, the mean plasma IGF-I concentrations were 80.8 +/- 25.1 ng/ml and 57.3 +/- 14.3 ng/ml respectively. Plasma IGF-I concentrations in pigs living at 4 degrees C were significantly lower than in pigs living at 20 degrees C (P < 0.05). Plasma glucose and non-esterified fatty acid (NEFA) concentrations in pigs at 4 degrees C were significantly higher than in pigs at 20 degrees C (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)