Selective Breeding: The Belgian Blue Cattle

Abstract
When comparing a Siberian husky to a Rottweiler there is a vast number of differences in their appearances; ears, color of coat and tails just to name a few. However, these dogs originate from the same species, but through artificial selection have become very different. Canines are one of the most common species that has been genetically altered to achieve a desirable appearance more pleasing to humans. Artificial selection is the process of selective breeding of closely related species (plant or animal) to achieve a more desirable trait in their offspring. Many different species have been altered through selective breeding. Selective breeding is a very common practice in the livestock breeding and has impacted the livestock industry
greatly by using information obtain from research of the myostatin protein.
History of selective breeding of cattle
In the 1800s the demand for a better quality as well as quantity of beef was high.
Cattle breeders begin to breed select breeds of cattle that appeared larger together in hopes of producing offspring with a larger quantity of meat. The selective breeding began with the Durham Shorthorns and Friesian cattle. (Lee, 2004) The result of the selective breeding produced 3 different strands of cattle breeds the Belgian Blue, Piedmontes and Parthenias. These breeds of cattle all have one similarity, that has proved to be very valuable, the inactive Myostatin protein. Due to the inactive Myostatin protein these cattle produce roughly 20 % more meat than other cattle. The Belgian Blue cattle are a common breed of cattle in the beef and livestock industry representing the double muscle trait caused by the inactive Myostatin protein.

Myostatin
In 1997 a research team from John Hopkins School of Medicine led by geneticists Dr. Se-Jin Lee and Alexandra McPherron released information from their research on how proteins regulate the growth of tissue in mice. Through their research the team unintentionally discovered the growth differentiation factor 8 (GDF-8) also known as Myostatin protein. With the discovery of the Myostatin protein the team decided to produce a mutant strain of mice that did not have
the Myostatin protein. The results showed that the mutant mice had 3 times the muscle tissue than that of a regular mouse. The research showed that with the absence of the myostatin protein the muscle tissue did not have anything to regulate the size; therefore muscle tissue was extremely larger. The Myostatin (GDF-8) protein is a member of the transforming growth factor β superfamily of secreted growth and differentiation factor. (Lee, 2004) Myostatin is a secreted protein that acts as a negative regulator of skeletal muscle mass. During embryogenesis, myostatin is expressed by cells in the myotome and in developing skeletal muscle and acts to regulate the final number of muscle fibers that are formed. (Lee, 2004) The research of Dr Se-Jin Lee and his colleagues brought the discovery of the Myostatin protein to the forefront of science. However they were not the only group of researcher. Two other research group have also reported finding on the Myostatin mutation. Micheal Georges of the University of Liege in Belgium and Timothy Smith of the U.S department of agriculture (USDA) in Clay Center, Nebraska have all contributed to the research of the Myostatin protein. Smith’s research team after many years of mapping research were able to pinpoint the location of the genetic defect causing muscular hypertrophy in double-muscled cattle to a small segment of bovine chromosome 2. (Dickman, 1997) With the information from Dr. Lee research team and the knowledge that had been obtain through their own research; Smith’s team was able to develop a DNA test for the different version of the mutated protein. (Lee, 2004) Dr. Lee’s team was also able to find the Myostatin protein pigs, birds, chicken and turkey.
Double Muscle Animals
The Belgian Blue cattle are known for the substantial amount of muscle tissue that has been created through artificial selection.
Cow breeders, who were under economic pressure from cheaper imports and high production costs, wanted to increase their yields and began to select for the double-muscling trait, which had been reported as early as 1807. Before long, nearly every beef cow in Belgium was a purebred double-muscled animal. (Dickman, 1997) Belgian Blue male cattle can weigh up to 1047lbs at one year old and up to 1709lbs at two years. The female Belgian can weight 816lbs at one year and 1102lbs at two years. In an extensive 3 year test, done by the USDA at the Meat Animal Research Center, Clay Center, Nebraska, the Belgian Blue crossbred cattle were tested with the industry standard Warner-Brazner shear test for tenderness. The Belgian Blue cattle had a lower shear value than the Hereford-Angus contemporary average, 12.8 versus 12.9, with comparable tenderness and flavor on the sensory panel. Belgian Blue cattle also exhibited less than half the fat cover, .21 inch cover versus .45 inch cover, a 53% reduction. Belgian Blue is on line for the new standards. The Belgian Blue also showed 16% less marbling and 14.2 more ribeye area than the average carcass. (Oklahoma State university,
1995)

Although the double muscle Belgian Blue produces a large amount of meat as well as a leaner meat there are still complications with the species. Due to the large size of the cattle all the births have to be done by cesarean section because the calves are too big to pass through the birth canal. Also calves may develop swelling of the tongue which makes nursing hard a cause premature death.
Artificial selection has had a significant impact on the livestock industry. Artificial selection has provided a solution to an economic problem. Being able to manipulate the size and quality of beef is a great accomplishment for livestock breeder.