Title

Effect of feed restriction on serum somatotropin, insulin-like growth factor-I-(IGF-I) and IGF binding proteins in cyclic heifers actively immunized against growth hormone releasing factor

Author Info

Jeffrey D. Armstrong, North Carolina State University at RaleighFollow
W. S. Cohick, University of North Carolina at Chapel Hill
R. W. Harvey, North Carolina State University at Raleigh
E. P. Heimer, Hoffmann-La Roche, Inc., Nutley, New Jersey
R. M. Campbell, Hoffmann-La Roche, Inc., Nutley, New Jersey

Recommended Citation

Postprint version. Published in Domestic Animal Endocrinology, Volume 10, Issue 4, October 1, 1993, pages 315-324.

Copyright © 1993 Elsevier.

NOTE: At the time of publication, the author Jeffrey D. Armstrong was not yet affiliated with Cal Poly.

The definitive version is available at https://doi.org/10.1016/0739-7240(93)90035-A.

Abstract

Feed restriction often increases serum somatotropin (ST) and decreases insulin-like growth factor-I (IGF-I) in ruminants; however, the mechanisms responsible for this change in ST and IGF-I are not well defined. We investigated the effects of feed restriction on serum ST, IGF-I, IGF binding proteins (IGFBP), insulin and nonesterified fatty acids (NEFA) in cyclic Angus and Charolais heifers (n=15) previously immunized against growth hormone releasing factor (GRFi) or human serum albumin (HSAi). Cows were fed a concentrate diet ad libitum (AL) or were restricted to 2 kg cotton seed hulls (R) for 4 d. Each heifer received each dietary treatment in a single reversal design. As anticipated, GRFi decreased ST, IGF-I and insulin (P