Comparison of muscle fiber types from 2-year-old fillies of the Belgian, Standardbred, Thoroughbred, Quarter horse and Welsh breeds.

The study investigates the composition of different muscle fiber types in the biceps femoris and triceps brachii of five breeds of young, female, untrained horses; Belgian, Standardbred, Thoroughbred, Quarter Horse, and Welsh ponies.

Overview of the Research

• The research focused on determining the percentages of three distinct muscle fiber types in two significant muscles, biceps femoris and triceps brachii, of five breeds of horses.
• The horse breeds included in the research were Belgians, Standardbreds, Thoroughbreds, Quarter Horses, and Welsh ponies.
• Biopsies were extracted from each of the two muscles from four 2-year-old, untrained fillies of each breed.
• The three types of muscle fibers investigated were red, white, and intermediate fibers.

Methodology

• The muscle fiber types were identified using tissue samples stained for succinic dehydrogenase activity, an enzyme involved in cellular energy production.
• The three fiber types include red (slow-twitch) fibers, white (fast-twitch) fibers, and intermediate (moderate-twitch) fibers.

Main Findings

• Amongst all breeds, intermediate fibers were found to be the most abundant.
• The distribution of red and white fibers varies significantly depending on the breed of the horse.
• Thoroughbred horses had the highest percentage of red (slow-twitch, endurance-dominant) fibers. These fibers are ideal for endurance as they use oxygen efficiently for sustained energy.
• Belgian horses, on the other hand, had more white (fast-twitch, strength-dominant) fibers. These fibers are better suited for short, speedy activities as they generate power and speed rapidly but fatigue quickly.