Submitted to: Global Aquaculture Advocate
Publication Type: Trade Journal
Publication Acceptance Date: 6/8/2007
Publication Date: 9/1/2007
Citation: Peterson, B.C., Small, B.C., Waldbieser, G.C., Bosworth, B.G. 2007. Gene-Based Markers Could Aid Selective Breeding. Global Aquaculture Advocate September/October p. 93. Interpretive Summary: At the Thad Cochran National Warmwater Aquaculture Center in Stoneville, MS, we tested the hypothesis that genes and gene products associated with the growth regulatory axis and stress axis could be used to explain differences in growth performance. We found that insulin like growth factor-II (IGF-II) mRNA levels in muscle were higher in fast growing families compared to slow growing families of catfish. We also found a negative correlation between weight gain and cortisol response to stress. These results suggest that the variation in growth among families of USDA 103 catfish is explained, in part, by variation in growth and stress axes. IGF-II could potentially be a candidate gene whose expression may reflect differences in muscle growth. We will further examine the relationship between stress responsiveness and weight gain toward our goal of identifying catfish with superior growth characteristics.
Technical Abstract: Research was conducted to examine the hypothesis that genes or gene products associated with the growth regulatory and stress axes could be used to describe differences in growth performance of USDA303 channel catfish (Ictalurus punctatus). Research examined mRNA levels of genes involved in the growth hormone-insulin like growth factor (GH-IGF) network in fast (Family A) and slow (Family H) growing USDA303 catfish. Fish (59.0 +/- 2.4 g) were fed for 7 wks, weighed, and tissues were taken for RNA extraction. The remaining fish were subjected to an acute 10-min dewatering stress. IGF-II mRNA was higher (P < 0.05) in muscle of fast growing compared to slow growing fish while levels of IGF-I receptor (IGF-IR) and IGF-IIR were similar. Muscle IGF-IIR mRNA was two-fold higher than muscle IGF-IR mRNA. There were no differences in liver and muscle IGF-I and GH receptor mRNA, or pituitary GH mRNA between the fast and slow growing fish. Fast growing fish consumed 135% more feed compared to slow growing fish, however abundance of ghrelin mRNA in the gut and neuropeptide Y mRNA in the hypothalamus were similar. Cortisol levels were negatively correlated (r = -0.47; P < 0.05) to weight gain. These results suggest that variation in growth among fast and slow growing USDA303 catfish is explained, in part, by variation in the GH-IGF and stress axes. The relationship between cortisol and weight gain warrants further investigation for possible exploitation into our selective breeding program.