Myosin heavy chain profiles and body composition are different in old versus young Standardbred mares.

The research article investigates differences in muscle composition and body fat related to aging in Standardbred mares. The results found a variation in myosin heavy chain (MHC) profiles and differences in lean body mass between younger and older mares, while fat mass and body weight remained largely consistent.

Research Objective

• The goal of the study was to investigate age-related changes in skeletal muscle composition and body fat in Standardbred mares, a topic that has relatively limited data in the realm of equine research.
• More specifically, the team aimed to analyze the concentration of muscle myosin heavy chain (MHC) – a protein responsible for muscle contraction – and how its distribution changes with age.

Methodology

• Overall, 31 mares were evaluated in this study, separated into two age groups, young (4-8 years) and old (20+ years).
• The team measured the rump fat thickness of these mares using B-mode ultrasound, and calculated percentage body fat. They also took needle muscle biopsies from the right gluteus medius muscle of each mare to evaluate MHC composition.
• The MHC composition was determined using sodium dodecyl sulphate-polyacrylamide gel electrophoresis, a process used to separate proteins by mass and charge. The muscle fibers were then identified as type I, type IIA, and type IIX, and quantified using a scanning and densometric system.

Findings

• No significant differences were found between old and young mares in their fat percentage, fat mass, or body weight.
• However, the study did reveal that older mares had a greater lean body mass than their younger counterparts.
• There were significant differences in the MHC composition, with the older mares having fewer type I and IIA fibers but more type IIX fibers, a finding consistent with age-related changes observed in other species.

Implications

• The research contributes valuable data on age-related changes in body composition and skeletal muscle in horses, specifically Standardbred mares.
• Understanding these changes can provide insight into equine health and fitness, which may guide future care and training approaches for both young and old horses.