You've reached the Virginia Cooperative Extension Newsletter Archive. These files cover more than ten years of newsletters posted on our old website (through April/May 2009), and are provided for historical purposes only. As such, they may contain out-of-date references and broken links.
To see our latest newsletters and current information, visit our website at http://www.ext.vt.edu/news/.
Newsletter Archive index: http://sites.ext.vt.edu/newsletter-archive/
Coding system identifies carriers of undesirable recessive traits
Dairy Pipeline: May 2001
Bennet Cassell
Extension Dairy Scientist,
Genetics and Management
540-231-4762
Email: bcassell@vt.edu
Widespread use of AI around the world and selection for similar traits across dairy populations has reduced diversity of pedigrees of influential cows and bulls. The frequency of carrier to carrier matings for undesirable recessive characteristics has increased as relationships between cows in dairy herds and bulls in AI service has increased in recent years. The dairy breed societies in the United States have implemented good systems for identifying carriers of undesirable recessive genes. When an animal is established as a carrier of an undesirable recessive, the information is published as part of an animal's identification. New genetic technologies have enabled scientists to establish "non-carrier" status for several genetic conditions, and codes have been developed for these as well. Following are the codes currently applied to Holstein animals. Codes referring to coat color hardly qualify as "undesirable", but are informative, nonetheless.
Recessive gene codes
| BD - Bulldog | HL - Hairless |
| MF - Mule-foot (syndactylism) | DF - Dwarfism |
| PG - Prolonged gestation | IS - Imperfect skin |
| BL - BLAD | B/R - Black-red animal |
| PT - Pink tooth (Porphyria) | DP - DUMPS |
| RC - Red hair color |
Recessive tested codes
| TM - Free of mulefoot | TL - Free of BLAD |
| TD - Free of DUMPS | TR - Free of red hair color |
The Jersey breed reports carriers of limberleg (LL) and rectovaginal constriction (RVC). The Brown Swiss breed identifies carriers of Weavers condition (W) as well as animals tested free of Weavers (TW). This listing is not necessarily exhaustive, and additional undesirable recessive genes will be added to these lists as they are discovered in years to come. All the breed societies and AI organizations deserve the support and praise of dairy producers for their commitment to the control of undesirable recessives through testing and open disclosure of carrier status.