Insulin resistance is a complex pathophysiological condition that appears to underlie a number of chronic conditions often collectively called equine metabolic syndrome,including laminitis,obesity,and osteochondrosis (OC).In the horse,the effects of diet and exercise on insulin resistance have been examined,but few studies have investigated insulin resistance and bone development or in the pregnant mare.OC is a developmental disease caused by a defect in the normal process of bone formation resulting in the thickening,cracking and tearing of the joint cartilage of growing horses.In the most advanced stages the condition is termed Osteochondrosis Dissecans (OCD).This condition is known to be associated with dietary deficiencies and/or nutrient imbalances,biomechanical stress or trauma,rapid growth rates,and genetic influences.The other interesting aspect of this problem is that it is often seen in very young foals which suggests that the bone formation problems were initiated prior to birth.