## 3 Producing High-Quality Beef--The Certified Angus Beef(r) Brand
### The Defining Phenotypic Characteristics of Angus Cattle  
The Aberdeen Angus breed originated in northeastern Scotland in the early 19 th century. Developed primarily in the counties of Aberdeenshire and Angus, the breed was created by selecting for high-quality beef traits in native polled cattle. The breed quickly became known for its superior meat quality, characterised by fine marbling and tenderness. Introduced to the United States in the 1870s, Angus cattle gained popularity and became a foundational breed for beef production. Today, Angus cattle are recognised worldwidefor their beef quality and adaptability to various environmental conditions. Angus cattle are naturally polled and characterised by their solid black or red coat colour ([[http://www.thecatllesite.com/breeds/beef/7/aberdeen-angus/](http://www.thecatllesite.com/breeds/beef/7/aberdeen-angus/)]([http://www.thecatllesite.com/breeds/beef/7/aberdeen-angus/](http://www.thecatllesite.com/breeds/beef/7/aberdeen-angus/)), accessed on 15 February 2024). They are characterised by having high muscularity, increased growth rates, greater body width, and a medium height [11]. The USDA Schedule GLA identifies Angus cattle as predominantly (51% or more) solid black colour [8], but the standard contains other criteria, such as being traceable back to provable Angus parentage, specifically that the qualifying cattle'must be traceable to one registered parent or two registered grandparents'. Phenotypically they must not display non-Angus characteristics, such as having dairy conformation, Holstein characteristics, or Brahman-type humps and dewalps.  
There are several genes that contribute in a dominant fashion to the Angus phenotype. Firstly, almost all offspring of Angus sires and some Angus-composite sires have the Angus coat colour phenotype. A dominant trait, Angus cattle are homozygous for solid black colour, which leads to all their progeny being black, even if mated to dairy cows. The gene associated with this black coat colour is \(MC1R\). It encodes the melanocortin 1 receptor (\(MC1R\)), which binds the melanocyte-stimulating hormone (\(\alpha\)-MSH) that affects eumelanin synthesis. \(MC1R\) is also known as the Extension (E) locus, and is located on bovine chromosome 18.  
Mutation in \(MC1R\) has been the subject of many studies in various species of mammals, including cattle [12; 13; 14], where the occurrence of a functional mutation has been associated with black (or dark) coat colour, while a lack of mutation at the \(MC1R\) locus has resulted in red, yellow, or white colours. Three alleles have been distinguished at the locus: the dominant black allele (E\({}^{\text{D}}\)), the recessive red allele (e), and the E\({}^{+}\) allele, which enables the expression of the separate A locus. The order of allele dominance is usually described as E\({}^{\text{D}}\) > E\({}^{+}\) > e. Studies [12] have illustrated that information obtained by sequencing, or other methods, can be used to identify the three alleles of \(MC1R\).  
Nearly all Angus cattle and most Angus-composite sires are homozygous polled, meaning that all their progeny are polled. This is a defining and highly valued Angus characteristic, but it is far less common in dairy cattle genetics and other beef breeds like the Hereford or Charolais. Angus cattle can also be defined by their classic beef phenotype: having a short head, broad muzzle, and muscular build, albeit characteristics are also true of other beef breeds. It does contrast the typically lean, 'low-muscle' characteristics of dairy cows.