Insulin-like growth factor I in growing thoroughbreds

W. B. Staniar, D. S. Kronfeld, R. M. Akers, P. A. Harris

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


The objective of this longitudinal study was to characterize growth and plasma insulin-like growth factor I (IGF-I) concentrations in pasture-raised thoroughbreds fed two sources of dietary energy. Mares and foals were randomly assigned to either a sugar and starch (SS) or fat and fibre (FF)-rich feed, and plasma IGF-I and growth were measured once a month from 1 to 16 months of age. These dependent variables were also compared with day length and ambient temperature. There was an association between plasma IGF-I concentration and average daily gain (ADG) (r = 0.32, p < 0.001). There were also clear seasonal patterns in both ADG and plasma IGF-I, with high values in June and May, and a low value in March. Plasma IGF-I and ADG were positively associated with day length and temperature. Plasma IGF-I was never higher (p > 0.10) in the FF group when compared with the SS group, and was higher in the SS group during a rapid growth phase in the spring of year 2 (p < 0.10). The results establish an association between ADG and IGF-I in the horse and indicate that environment and age may influence this relationship. In addition, plasma IGF-I is influenced by dietary energy source at particular times of year. This link has important implications in designing feeding management strategies that are aimed at addressing skeletal development.

Original languageEnglish (US)
Pages (from-to)390-399
Number of pages10
JournalJournal of Animal Physiology and Animal Nutrition
Issue number9-10
StatePublished - Oct 2007

All Science Journal Classification (ASJC) codes

  • Food Animals
  • Animal Science and Zoology


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