Comparison of Muscle Fiber types from 2-Year Old Fillies of the Belgian, Standardbred,
Thouroughbred, Quarter Horse and Welsh Breeds
Introduction
Horses have been chosen by their different breeds for thousands of years to
perform different tasks. You have the working class horses and horses which have been
bred for speed. Scientists performed this research because the horse world wants to know
how the muscle fibers of different breeds vary, and if muscle fiber composition can
determine how well a horse will be able to perform within their given commerce. They
were trying to see all of the muscle fibers within the horses and questioned if it might be
possible to examine fiber composition of selected muscles at an early age. This would
better predict the horse’s potential for the future (Albert, Stull p 342).
There was a study done by Guy and Snow (1977) in which they compared the
percentages of "white plus intermediate fibers in Thoroughbred, Standardbred, and
ponies." They found proportions of roughly 80.5, 72, and 74%. The age, sex, and
training of these horses were never mentioned (Guy, Snow 1977).
Materials and Methods
The experiment that was done on the different breeds of horses is that they stained
the muscle fibers within different regions of the horses’ legs. The group with which they
did the experiment on was four untrained two year old fillies from different groups
including the Belgian, Standardbred, Thoroughbred, Quarter Horse and Welsh breeds. In
order to extract muscle portions they put some "Rompun" which is an analgesic and a
sedative. They then extracted a 7.5 x 7.5 cm piece of muscle from each of the fillies
which they had. They took tissue samples from the biceps femoris and triceps brachii.
After the extraction had taken place, there was great care to make sure that the fillies
received a proper cleansing followed by disinfection. Following the extraction and
staining of the muscle tissues each was cut down to 10 to 12 mm and transferred to some
slides for further investigation. Each of the muscle samplings were photographed twice,
while each had approximately 50 muscle fibers. The fibers were set apart based on the
intensity with which they were stained. They ranged from very oxidative (red/fast
contracting), to the least oxidative tissues (white/slow contracting), while the
intermediate (more of a pinkish color) were established.
Results
The results were that the most common muscle tissues of all the horses were in fact
the intermediate tissues. Thoroughbreds were found to have the highest ratio of red to
white tissues, while Belgians were found to have the highest ratio of white to red tissues.
There was not, however, a large distinction between the horse breeds and the muscle
tissues found there-in. The study also showed that from muscle taken from each of the
sections of the fillies, there was no major difference between the biceps femoris and
triceps brachii regions.
Discussion
There was a big conclusion reached within this study. It just goes to show that
there are three types of muscle tissue found within all of the horses. They may consist of
slightly different ratios, but still all have the same tissue types. From the research it may
suffice to say that Thoroughbreds more oxidative capacity and higher red to white muscle
fibers makes them best suited for the race track and speed. The study also shows the
opposite and the reason that the Belgian, more of a workhorse, contains a greater ratio of
white to red tissues.
Works Cited
Guy, P.S. and D.H. Snow. 1977. The effect of training and detraining on muscle
composition in the horse. J. Physiol. 269:33.
Stull, C. L., and W. W. Albert. "Comparison of Muscle Fiber Types from 2-Year Old
Fillies of the Belgian, Standardbred, Thouroughbred, Quarter Horse and Welsh
Breeds." Journal of Animal Science 51.2 (1981): 340-43. Print.