Can Diet Affect Growth Hormones in Young Horses?

Hormones such as insulin, thyroxin, triiodothyronine, and cortisol control growth in young horses. Nutrition influences metabolic pathways and may affect hormone profiles. The objective of this study was to determine whether high-carbohydrate or high-fat diets affect certain hormone profiles associated with growth in horses.

In the study, 11 Thoroughbred, Quarter Horse, and Arabian horses aged 9 to 10 months old were assigned to one of two groups and were fed either high-energy (high carbohydrate) or high-fat diets containing the same caloric levels. Soybean oil was added to a basal diet for the high-fat group. Alfalfa hay was also fed. The horses were evaluated for obvious growth abnormalities at the beginning, midpoint, and end of the trial. They were weighed and measured weekly. Venous blood samples were taken before feeding and at 30 and 90 minutes after eating.

There was no difference in hip height, wither height, or heart girth related to diet. There was no visual evidence of bone development problems. In phase 2, glucose concentrations were higher for the high-carbohydrate diet than for the high-fat diet. Average insulin concentrations were also higher for the high carbohydrate than for the high-fat diet in the second phase. Cortisol concentrations were lower in the high-fat groups before feeding. Horses moving from the high-fat diet to the high-carbohydrate diet showed higher intakes and higher weight gains.

It is known that elevated glucose and insulin levels in growing horses have the potential of dramatically affecting growth. More study is required before dietary manipulation of growth in horses can be achieved.

This report of KER’s 1989 research was published in Proceedings of the 11th Equine Nutrition and Physiology Society Symposium.

Read the entire research paper, titled Influence of Isocaloric High Energy Carbohydrate and Fat Diets on Growth-Related Hormone Profiles in the Yearling Horse.