Buying bulls is like making soup. You put in a bit of this and a bit of that and in the end, you have good soup. Likewise, a piece of this and a piece of that and you assemble a good bull. Unlike the soup you make from scratch, the bull already is made, but you have to find him.
Ultimately, the bull will supply half the pieces for your next calf crop. So what are the pieces? Just like soup, every spoonful should be complete and savored. When the spices are added, they literally dissolve into every spoonful.
Likewise, when the bull's DNA is added to the herd, the DNA literally dissolves into the calves and all future generations.
With today's technology, those pieces of DNA can be detected and isolated generations later. Even more so than the bull, the herd is this massive pool of genes that produce a working, manageable herd.
So how does one know what genes one has in the herd? There are a few traits such as certain colors or horns that are the result of a single gene and can be detected and screened for fairly easily.
Another example is the many genetic defects in cattle where a single gene has caused a "kink" in the production line so calf deformities are the end result.
These single genes can float around and occasionally express themselves.
However, production genes are our main interest today. Production genes are best managed through the utilization of expected progeny differences (EPDs). They are not seen individually and are expressed best if allowed to work as a team.
Unlike adding salt or spice to a soup, production genes are more like the meat and potatoes.
Production genes determine how an animal exists, such as fast or slow daily gains, how heavy the calf is at birth, how well the calf grades, how large the rib eye is or even how much milk the cow will produce. The list is long and the traits are numerous.
These production genes are named by the effect they are expected to have on a particular trait. For the sake of understanding, let's visit five of these traits. The five are birth weight (BW), weaning weight (WW), yearling weight (YW), marbling (MARB) and rib-eye area (REA).
The process is linked to the various breed associations that register cattle and provide EPDs. For discussion purposes, let's use the Red Angus Association's website (http://redangus.org/). EPDs are defined by each breed association, but the basic EPDs have the same definition. Each breed also has unique traits identified as important and different selection indexes that breeders have identified as significant for their breed.