Before any decisions can be made about culling animals from the herd, the cow owner or manager must make two decisions: 1) which production traits are most desirable, and 2) what priority should be given to each trait.
The information to use in determining which cows to cull comes from two sources: 1) information supplied by the animal's own performance, and 2) information that compares the animal to the herd or group.
Each female entering the herd must meet these critical performance levels: breed early in the breeding season (first 40 days); deliver a live calf; rebreed on schedule (within 80 to 90 days after calving), and wean a calf.
After a cow meets these necessary performance levels, other culling criteria should be of a comparative nature. The most important of these is the size or weight of her calf. This can be established fairly only by comparing the calf's weight or standing within an age group for a particular year or similar environment.
Economically important traits that need to be selected for and retained in the herd are reproduction, functionality and production.
Heifers should calve at two years of age and raise a calf to weaning. Cows should rebreed and calve every 365 days under the environment in which they are maintained with a minimum of supplemental feed.
A replacement heifer development program, which allows for the breeding of more heifers than are needed (with final selection based on how early the heifer breeds), will have a positive effect on reproduction. Selection pressure should be toward heifers and cows that breed and rebreed early in the breeding season.
Open cows are the greatest contributors to low weaning percentages. On average, a cow that does not breed one time will lose 15 percent to 20 percent of her lifetime production potential. It will take the net return from two to three productive cows to pay for the maintenance of the open cow.
An unusually high number of open cows warrants a serious investigation. Diseases in the cow herd or bull reproductive problems could be the cause.
It would make more economic sense to sell the open cows and buy bred cows or bred heifers that have known genetic and health backgrounds rather than to wait two years for these open cows to wean their next calves, providing they conceive when next exposed.
Research has shown that open cows conceive only about two-thirds of the time. Death loss, infertility, low productivity and advanced age may result in the culling of 15 percent to 25 percent of the cow herd annually.
With the high cost of replacement heifer development, longevity becomes extremely important. Evaluate the soundness of mouth, feet, legs and udders. Cull cows with problems. Examine the eyes. Salvage cows exhibiting any signs of cancer eye before they are discounted at the market place.
Remove cows that have previously prolapsed or exhibited any other physical impairment that would increase management needs and costs in producing a calf.
The cow should provide enough milk to wean a calf that will reach the weight goal set by the manager. Genetic ability for growth is important. The most reliable means of making genetic progress for economically important traits is to utilize superior sires. If the replacement heifers are produced within a herd, 87.5 percent of the genetics contained in the calf crop will come from the last three sires or groups of sires used in the herd.
After culling for reproductive efficiency and functionality, make decisions regarding weaning weights that are a highly correlated measure of cow productivity. Individually identified cows and calves, known birth dates and calf weaning weights are highly desirable. An accurate set of records will provide the basis for evaluating performance and making management decisions with greater accuracy.
However, by simply pairing calves with their dams, a manager can identify early‑calving cows and/or those producing later, heavier calves. Culling cows that produce lightweight calves will improve overall herd productivity. When individual calf weights are obtained, they can be adjusted for age and sex of calf, as well as age of dam.
Although these adjustments do allow for maximum genetic evaluation, they do not take into account the environmental factor that may be responsible for a cow weaning a younger calf.
This can have a detrimental effect on the commercial producer who might be selling pounds at weaning or who is trying to develop a cow that will produce under a certain set of environmental conditions. In these cases, give preference to evaluating performance based upon actual weaning weights within sex and age group of the cow (with two- and three-year-olds' offspring being compared separately from those of the mature cows).
However, the cost of developing a replacement female to the point where she offers some return in the form of a weaned calf may suggest keeping the cow, if she gave birth to a calf and the reason for her not weaning it was due to something other than calving difficulty.
Support for this decision would be enhanced if she rebred early. This is where a complete set of records can help make the decision. If the cow is an aboveaverage producer, has not missed weaning a calf before and is relatively young (five years of age or less), it may be advantageous to keep her.
However, if a producer has developed an effective genetic improvement program through superior sire selection, the improved performance in a bred heifer in comparison to a below‑average cow could well make up the production difference between the cow and heifer. Also, the increased salvage value of the cow will aid in covering the cost of heifer development.
(Reprinted from the Texas Beef Cattle Management Handbook. The entire book can be ordered from Texas A&M University by calling (409) 845-3579.)