Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2003
Publication Date: 10/27/2003
Citation: Pagan, M., Davis, M.E., Stick, D.A., Simmen, R.C., Raney, N.E., Tempelman, R.J., Ernst, C.W. 2003. Evaluation of serum insulin-like growth factor binding proteins (igfbp) in angus cattle divergently selected for serum igf-i concentration. Domestic Animal Endocrinology. 25(4):345-358.
Interpretive Summary: IGF-I is a growth factor that is regulated by growth hormone. Cattle have been bred to have high IGF-1 levels to increase growth. I is not clear just how other hormone-related parameters are affects bu the high IGF-1 levels. In this study, cattle that had either high or low serum IGF-I levels were studied to learn more about a protein to which IGF-1 binds and it carried in the blood to target tissues. This study showed that while selection for high versus low serum IGF-I concentrations has resulted in changes in body weights, it has not resulted in changes in serum IGF-Binding Protein (IGF-BP2) levels. Furthermore, circulating IGFBP-2 appears to be higher in heifers than in bulls, and also appears to be negatively correlated with body weights.
Technical Abstract: Postweaning serum insulin-like growth factor-I (IGF-I) concentrations and serum IGF binding proteins (IGFBP) were investigated in 68 (1992 Fall-born) and 84 (1999 Fall-born) Angus cattle selected for either high or low serum IGF-I concentrations since 1989. Relative serum levels of IGFBP were determined by [125I]IGF-I Western ligand blotting. IGFBP species of 38'42, 34, 30, and 24 kDa were identified. The 34 kDa species was identified as IGFBP-2 by immunoblot analysis. No significant line effects were observed for any of the IGFBP. In both 1992 and 1999, heifers had higher IGFBP-2 levels than bulls (P<0.0005). In 1992 calves, relative levels of the 38'42 and 24 kDa species were significantly correlated with serum IGF-I concentration. In 1999 calves, none of the IGFBP were correlated with serum IGF-I, although IGFBP-2 was negatively correlated with several measures of body weight. No significant line effects were observed for growth or serum IGF-I traits in 1992 calves. However, 1999 high line calves had higher serum IGF-I concentrations and body weights than low line calves (P<0.05). In both 1992 and 1999 calves, bulls had higher serum IGF-I concentrations and body weights than heifers (P<0.05). Thus, while selection for high versus low serum IGF-I concentrations has resulted in divergence between the selection lines and also in changes in body weights, it has not resulted in changes in serum IGFBP levels. Furthermore, circulating IGFBP-2 appears to be higher in heifers than in bulls, and also appears to be negatively correlated with body weights. Author Keywords: Beef cattle; Insulin-like growth factor binding proteins; IGFBP-2; IGF-I; Selection