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Endocrine Events Prior To Puberty In Heifers: Role Of Somatotropin, Insulin-Like Growth Factor-I And Insulin-Like Growth Factor Binding Proteins, Jeffrey D. Armstrong, R. L. Stanko, W. S. Cohick, R.B. Simpson, R. W. Harvey, B.G. Huff, D. R. Clemmons, M.D. Whitacre, R.M. Campbell, E.P. Heimer
Endocrine Events Prior To Puberty In Heifers: Role Of Somatotropin, Insulin-Like Growth Factor-I And Insulin-Like Growth Factor Binding Proteins, Jeffrey D. Armstrong, R. L. Stanko, W. S. Cohick, R.B. Simpson, R. W. Harvey, B.G. Huff, D. R. Clemmons, M.D. Whitacre, R.M. Campbell, E.P. Heimer
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We have utilized active immunization against growth hormone releasing factor (GRF) to investigate relationships among somatotropin (ST), insulin-like growth factor-I (IGF-I), IGF binding proteins (IGFBP) and ovarian function in heifers. Active immunization against GRF (GRFi) has been demonstrated to abolish episodic release of ST and decrease serum concentrations of IGF-I. In initial experiments investigating onset of puberty, breeds of heifers differing in growth rate and reproductive traits (Angus, Charolais and Simmental) were immunized against GRF or served as controls (immunized against carrier protein, human serum albumin, HSAi). GRFi decreased rate of muscle and skeletal growth, but increased deposition of adipose …