For as long as animals have been domesticated, people have been actively changing how they look and perform.
Size, color, body shape, milk production, and many other traits have been tinkered with in efforts to produce "better" animals. We would like to think our selection processes have improved the value of our animals. Whether this is true or not is determined primarily by how much emphasis we place on which traits.
The process can go wrong in several different ways but the main problem will usually be a poor understanding of what makes money and what does not. The current population of oversize cattle – bred to fit the box and meet the demands of the trade – is an example. These animals are poorly suited for production as grazing animals, yet at least two thirds of their slaughter weight and probably 90% of their parents' mature weight will be grown on grass.
Selecting for traits of low importance reduces the ability to select for more important traits. Even more damaging is selecting for the wrong traits.
I spent some time in high school and college judging livestock and got pretty good at identifying animals that met the breed standards. Problem is some of the breed standards have little to do with improving animal function and some are actually harmful.
Two examples come to mind: First, the insistence of the Hereford breeders that their cattle have no color in their faces when that lack of color around the eyes promotes cancer of the eye. Second, the Santa Gertrudis breed throwing out light-colored cattle even though they have superior heat tolerance compared to the deep cherry red called for in the standards.
Similar examples of selection for "pretty" can be found in most breeds of animals, from dogs and cats to food animals. The breed associations are not the only culprits; academia and producers quite frequently base their selection criteria on traits that have no relationships to animal functionality (or inverse ones). The more importance we place on trivial things, the less selection pressure we can apply to the important things.
We are all prone to carry things to extremes; "If big is good, bigger must be better" is a common attitude. We would be wise to copy nature. Extreme phenotypes seldom perform well in the natural world. While it is true that we can increase production by adding inputs, every dollar spent on inputs is a dollar put at risk, and the increased production lasts only as long as the money flows. An expense that re-occurs regularly should be a red flag signaling there is an opportunity to improve the operation by a change in management.
How, then, do we design a breeding program that will reliably turn out animals capable of profitable production? The logical start will be to identify those traits that contribute to profitability; early maturing, easy fleshing and low maintaince come to mind.
For a cow-calf program, fertility is always important and usually the most important. This can be measured as the value of calf sold per cow exposed but the value to the operation goes beyond this monetary figure. Fertility, as commonly measured, has low heritability. The reason is because fertility is the product of numerous other factors: Hormonal balance, metabolic function, immune system function, grazing effectiveness, parasite resistance, climate adaption, and other factors all contribute to fertility or the lack of fertility. It is a measure of the total fitness of an animal to its environment. If any one of the governing factors is subnormal, fertility will suffer.
The way to develop animals that perform well is simply to select replacements from the animals, male and female, that perform well under your conditions and your management. A simple way to do this is to expose all of a crop of heifers to the bulls and make cows out of the ones that calve in the first twenty three days of the calving season.
Keep bulls from cows that consistently calve early, stay in good body condition, and show resistance to parasites.
Not exactly rocket science but it works. The animals selected in this manner will be the ones best suited to your conditions. The eye of the master does fatten the ox.