High glycemic and insulinemic responses to meals affect plasma growth hormone secretory characteristics in Quarter Horse weanlings.

This study investigates the relationship between different types of meals and how they affect the secretion of growth hormone in young horses. The research found that high-glycemic meals delay the first pulse of growth hormone secretion and increase its secretion during late night hours compared to low-glycemic meals.

Objective of Study

The aim of the study was to analyze how meals varying in glycemic responses, designated as high-glycemic (HG) and low-glycemic (LG) affect the secretion patterns of growth hormone (GH) in growing young horses. The researchers were motivated by the key role played by GH in the process of growth, and the importance of metabolic functions and nutrition regulation.

Study Methodology

• The study was conducted on twelve Quarter Horse weanlings (aged approximately 5.4 months) following a crossover design.
• It contained two 21-day periods and two treatments where horses were fed either a HG or LG concentrate meal, twice daily. In addition, the horses were allowed unlimited access to hay.
• Throughout the final day of each period, blood samples were taken at fifteen-minute intervals over 24 hours. These samples were used to measure levels of plasma glucose, insulin, non-esterified fatty acids, and GH.
• To estimate the GH secretion patterns, deconvolution analysis was used.

Outcome of the Study

• Through the analysis, it was observed that after a meal, horses fed with HG exhibited a longer delay until the first pulse of GH secretion compared to those fed with LG.
• Also, during late night hours (between 1:00 AM to 6:45 AM), HG horses secreted more pulsatile GH than LG horses.
• The results show potential associations between glycemic and insulinemic responses to meals and GH secretion patterns.

Significance of Results

The study helps understand how the source of dietary energy and metabolic disturbances caused by feeding HG meals can alter GH secretion patterns in growing horses compared to LG meals. This has potential implications on the growth and development of different tissues in young horses and could be critical in designing the optimal diet to ensure proper physical development.