Grain Meals and Growth Hormone Production in Weanling Horses

Research has shown that some types of equine skeletal problems can be minimized by managing foals and weanlings to produce smooth, gradual growth planes that avoid serious lags or steep rises. In particular, low-glycemic feeds have been linked to healthier growth patterns.

A study conducted at Pennsylvania State University may help to explain the mechanism by which large starch-laden grain meals can disrupt safe growth patterns in young horses.

Grain meals rich in carbohydrates are known to cause a rise in blood glucose followed by an insulin surge. The study was designed to test the theory that this glycemic/insulinemic response would signal the pituitary gland to stop secreting growth hormone (GH), a reaction that would be followed by a corresponding pulse of GH secretion a few hours later.

In the study, weanlings were fed either high-glycemic or low-glycemic meals. Results of blood analysis showed that a GH pulse occurred in all the horses after eating, but the pulse was delayed for an additional 26 minutes in weanlings that ate high-glycemic meals. These horses also had larger GH pulses between meals and overnight, resulting in a 33% increase in total GH production for the high-glycemic group.

Further research is needed to assess the effect of these GH variations on skeletal development in young horses.