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Insulin-like growth factor I in growing thoroughbreds
W B Staniar1, D S Kronfeld, R M Akers
1Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA. wstaniar@vt.edu
Journal of Animal Physiology and Animal Nutrition
|September 12, 2007
Summary
Growth and insulin-like growth factor I (IGF-I) in foals are linked to diet, season, and temperature. Diet type influenced IGF-I, impacting skeletal development strategies for young horses.
Area of Science:
- Equine Nutrition
- Animal Physiology
- Growth Biology
Background:
- Insulin-like growth factor I (IGF-I) plays a crucial role in mammalian growth.
- Dietary energy sources can influence growth and hormonal profiles in young animals.
- Environmental factors like temperature and photoperiod are known to affect physiological processes.
Purpose of the Study:
- To investigate the relationship between dietary energy sources (sugar/starch vs. fat/fiber) and growth parameters in Thoroughbred foals.
- To characterize plasma IGF-I concentrations and their correlation with growth in pasture-raised foals from 1 to 16 months of age.
- To assess the influence of environmental factors (day length, temperature) on growth and IGF-I levels.
Main Methods:
- Longitudinal study design with monthly measurements from 1 to 16 months of age.
- Random assignment of Thoroughbred mares and foals to either a sugar and starch (SS) or fat and fiber (FF) rich diet.
- Measurement of plasma IGF-I concentrations and average daily gain (ADG), correlated with day length and ambient temperature.
Main Results:
- A significant positive association was found between plasma IGF-I concentration and average daily gain (ADG) (r = 0.32, p < 0.001).
- Clear seasonal patterns were observed for both ADG and plasma IGF-I, peaking in late spring/early summer and lowest in March.
- Plasma IGF-I and ADG were positively associated with increasing day length and temperature. The fat and fiber (FF) diet did not result in higher IGF-I compared to the sugar and starch (SS) diet, though IGF-I was higher in the SS group during spring growth (p < 0.10).
Conclusions:
- Plasma IGF-I is a reliable indicator associated with average daily gain in horses.
- Environmental factors (age, season, temperature, day length) significantly influence the relationship between IGF-I and growth.
- Dietary energy source can modulate plasma IGF-I levels, particularly during specific growth phases, with implications for equine skeletal development management.
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