THE RELATIONSHIP BETWEEN PLASMA INSULIN-LIKE GROWTH-FACTOR-I (IGF-I) LEVEL AND BODY-WEIGHT IN THE HORSE

The relationship between plasma insulin-like growth factor-I (IGF-I) l evel and body weight was studied in six breeds of horse. The correlati on coefficients between plasma IGF-I and body weight in males and fema les of 1 year old heavy horses (Percheron and Breton breeds) were 0.62 and 0.12 respectively. The mean plasma IGF-I of males was higher than that of females (p<0.01). However, the plasma IGF-I levels of heavy h orses did not exceed those of light horses (Thoroughbred) or ponies (S hetland and Falabella). These data suggest that IGF-I is at least rela ted to the difference of body weights between sexes in heavy horses.