Changes in the metabolic profile of equine muscle from birth through 1 yr of age.

The research investigates the development and changes in the metabolic activity of the muscle tissues of horses in their first year, from birth. The study focused on the gluteus medius muscle biopsies of 11 quarter horses and 5 Standardbreds at various stages within that first year.

Methodology of the Study

• The study involved obtaining duplicate muscle biopsies from the central part of the gluteus medius which is located 2 cm below the superficial fascia. These samples were taken at intervals of 1 day, 7 days, 1 month, 3 months, 6 months, and 1 year for the quarter horses and at 1 day, and 3, 6, and 12 months for the Standardbreds.
• Key muscle enzyme activities were determined. These were citrate synthase, 3-hydroxyacyl-CoA dehydrogenase, phosphorylase and lactate dehydrogenase.
• The styles of fiber within the muscles – namely fast-twitch, fast-twitch high oxidative, and slow-twitch oxidative types – were established by using succinate dehydrogenase and myosin adenosinetriphosphatase (at a pH of 9.4) histochemical stains.

Results

• The study revealed that there were not significant changes in the percentages of histochemically determined muscle fiber-types as the horses aged within the first year.
• Lactate dehydrogenase activity significantly increased over the first six months, by threefold in the quarter horses and twofold in the Standardbreds.
• Similarly, phosphorylase activity also grew substantially – sixfold in the quarter horses and sevenfold in the Standardbreds over the same period.
• There were decreases in the activity of both citrate synthase and 3-hydroxyacyl-CoA dehydrogenase in the quarter horses during their first three months of life.

In conclusion, this investigation has provided understanding into the development of the metabolic activity in horses’ muscle tissues during the first year of their lives, showing increased lactate dehydrogenase and phosphorylase activities and variable changes in other enzymes.