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

J. D. Armstrong, W. S. Cohick, R. W. Harvey, E. P. Heimer, R. M. Campbell

Research output: Contribution to journalArticle

30 Scopus citations

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<.05). In addition, GRFi decreased serum IGFBP-3 (P<.01), but increased IGFBP-2 (P<.01). Feed restriction resulted in an increase in serum ST in HSAi, but not in GRFi heifers. Regardless of immunization treatment, feed restriction decreased serum IGF-I and insulin, and increased NEFA (P<.01). In conclusion, the increase in serum ST levels observed during feed restriction was blocked by active immunization against GRF. However, feed restriction resulted in decreased serum IGF-I in GRFi heifers in spite of initial low levels of IGF-I (due to GRFi). Although GRFi decreased levels of IGFBP-3 and increased levels of IGFBP-2, feed restriction for 4 d did not alter serum IGFBP.

Original languageEnglish (US)
Pages (from-to)315-324
Number of pages10
JournalDomestic Animal Endocrinology
Volume10
Issue number4
DOIs
StatePublished - Oct 1993
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Food Animals
  • Animal Science and Zoology
  • Endocrinology

Fingerprint Dive into the research topics of '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'. Together they form a unique fingerprint.

  • Cite this