Marker Assisted Selection has been focused early on in cows, as they are an important dairy animal. One study using MAS was done on cattle that were infected with mastitis, an udder infection due to bacteria. Mastitis makes a cow produce less milk, need more veterinary care, and after some time, kills the cow, making the disease a serious economic and welfare-related problem. Using gene maps from Scandinavia, scientists have used MAS to discover some loci that may be related to mastitis resistance. One promising locus is the Major Histo-compatibility Complex (MHS) locus.

Another study on cattle has been done regarding double muscling cows. Cows that have this mutation have double the muscle of an ordinary cow, hence its name. At first, researchers did not know what caused double muscling in cattle. However, the gene was mapped through MAS and was being analyzed. While the gene was being analyzed and possible markers were being found, another unrelated study for mice for a mutation similar to double muscling was being done. The mice study concluded that the reason for the mice’s mutation was due to an inactive myostatin gene. When the researchers re-analyzed their data on the cattle, they found that all cattle with double muscling were due to myostatin. All this was done through MAS.