Immunoreactive Insulin-Like Growth Factor in Plasma during Pre- and Post-Partum Periods of Thoroughbred Mares from which the Newborn were Removed

Plasma concentrations of immunoreactive (ir-) insulin-like growth factor I (IGF-I) were measured in 9 pregnant mares from 30 days before foaling to Day 7 after ovulation of the first post-partum estrus (foal heat) in order to characterize its pattern and investigate its possible role in mares during that time. A marked increase in plasma concentrations of ir-IGF-I was observed during the last month of pregnancy. After foaling, ir-IGF-I sustained its high concentration for the first week after parturition and it gradually decreased thereafter. Throughout the observation period of the current study, a significant positive correlation between ir-IGF-I and FSH (r=0.58, p