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ARS Home » Southeast Area » Stoneville, Mississippi » Warmwater Aquaculture Research Unit » Research » Publications at this Location » Publication #180855
Title: EFFECT OF FASTING ON NYCHTHEMERAL CONCENTRATIONS OF PLASMA GROWTH HORMONE (GH), INSULIN-LIKE GROWTH FACTOR I (IGF-I), AND CORTISOL IN CHANNEL CATFISH (ICTALURUS PUNCTATUS)

Author
item Small, Brian

Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2005
Publication Date: 8/26/2005
Citation: Small, B.C. 2005. Effect of fasting on nychthemeral concentrations of plasma growth hormone (gh), insulin-like growth factor i (igf-i), and cortisol in channel catfish (ictalurus punctatus). Comparative Biochemistry and Physiology B. 142:217-223.

Interpretive Summary: Farmed channel catfish are sometimes subjected to periods of restricted feeding as a means of managing poor water quality and disease outbreaks. Published research results suggest that feed restriction can negatively affect catfish hormone levels. In those studies, conclusions were based on measurements taken at a single point in time and may have been confounded by normal variations in blood hormone levels. To learn more about the effects of feed restriction on blood hormone levels in channel catfish, 24-hour hormone levels of fasted and fed catfish were measured in this study. Significant differences in blood hormone levels resulting from normal daily variations and from feed restriction were observed. This study illustrates the importance of feeding status and sampling time on blood hormone levels of this economically important species.

Technical Abstract: This experiment was conducted to characterize the effect of fasting verses satiety feeding on plasma concentrations of GH, IGF-I, and cortisol over a nychthemeron. Channel catfish fingerlings were acclimated for two weeks under a 12L:12D photoperiod, then fed or fasted for 21 d. On day 21, blood samples were collected every two hours for 24 hours. Weight of fed fish increased an average of 66.2%, and fasted fish lost 21.7% of body weight on average. Average nychthemeral concentrations of plasma GH were not significantly different between fed (24.7 ng/ml) and fasted (26.8 ng/ml) fish, but average nychthermeral IGF-I concentrations were higher in fed (23.4 ng/ml) verses fasted (17.8 ng/ml) fish. An increase in plasma IGF-I concentrations was observed in fasted fish 2-h after a peak in plasma GH, but not in fed fish. Average nychthemeral plasma cortisol concentrations were higher in fed (14.5 ng/ml) verses fasted (11.0 ng/ml) fish after 21 d. Significant fluctuations and a postprandial increase in plasma cortisol were observed in fed fish, and there was an overall increase in plasma cortisol of both fasted and fed fish during the scotophase. The present experiment indicates little or no effect of 21-d fasting on plasma GH levels, but demonstrates fasting-induced suppression of plasma IGF-I and cortisol levels in channel catfish.