Date of Graduation

8-2012

Document Type

Thesis

Degree Name

Bachelor of Science in Biological Engineering

Degree Level

Undergraduate

Department

Biological and Agricultural Engineering

Advisor

Carrier, Danielle Julie, 1959-

Reader

Osborn, Scott

Third Reader

Tipsmark, Christian

Abstract

Channel catfish (Ictalurus punctatus) are the most widely farmed aquatic animal in the United States. Assessing the effect of feeding regimens on their overall growth requires grow-out trials and a subsequent inefficient use of time and money. The growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis regulates growth based upon environmental factors such as feed intake in many teleost fish species. In order to increase the efficiency of aquaculture, the components of the GH/IGF-1 axis might be used as endocrine biomarkers to evaluate instantaneous growth rate. The goal of this study was to better understand the effects of feeding regimen on the regulation of growth in channel catfish. Accelerated growth during re-feeding periods after fasting is of particular interest. These periods, termed compensatory growth (CG) periods, have been observed in several teleost fishes. To study this, mRNA expression of GH/IGF-1 axis components was examined in the liver, skeletal muscle and pituitary of channel catfish during two weeks of fasting and one week of re-feeding with a control group of animals fed daily. In addition, hepatosomatic index (HSI) and condition factor (CF) were calculated for each fish. CF data suggests CG after only a week of re-feeding. Fasting induced a significant decrease (P<0.05) in HSI, which returned to normal after re-feeding. Fasting induced a significant increase in muscular ghr-1 (P<0.01) and a significant decrease in muscular igf-1 (P<0.001). Re-feeding induced a significant increase in hepatic igf-1 (P<0.001), igfbp-5a (P<0.01), igfr-1a (P<0.001), and ghr-1 (P<0.01) and in muscular igf-2 (P<0.01), igfbp-1 (P<0.001), igfbp-2 (P<0.01), igfbp-5a (P<0.05), and igfr-1a (P<0.05). Results indicate that the GH/IGF-1 axis is highly sensitive to re-feeding in channel catfish and that CG can be induced.

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