|"The first step in any selection or mating program is to decide what is your goal and what traits are economically important to you."
When it comes to pairing up bulls and cows, you might wonder if humans don't have the right idea. You can fill out a form that lists what you want, post it on the Internet and let the computer find potential matches for your herd. But, as with humans, the key to finding that perfect match is knowing what you are looking for first, and then determining the right strategy to get you to your goals.
In some cases, there are software programs that help you match cows to bulls that meet certain EPD criteria. Your seedstock provider can also help you decipher the numbers.
But when it comes down to it, genetic selection is really a balance between science and art, says Twig Marston, executive director of the Beef Improvement Federation and director of the Northeast Research and Extension Center at the University of Nebraska–
Lincoln. Before you buy bulls to put with your cows, you need to step back and create a breeding program that you can sustain while improving your herd's genetics.
Set goals. To achieve that balance, start with your goals. "The first step in any selection or mating program is to decide what is your goal and what traits are economically important to you," says Dorian Garrick, who holds the Lush Chair in Animal Breeding and Genetics at Iowa State University.
To read more on establishing a logical genetic strategy and choosing a breeding system, click here to read more specific details from Steve Hammock.
What's the difference between straightbreeding and crossbreeding systems?
• Same breed of sire and dam.
• Usually result in individuals rather uniform in appearance, but not necessarily in performance.
• But, if these individuals are not desirable, the uniformity is detrimental.
• Sire and dam of different breeds.
• Can be simple or complex to operate.
• Uniformity of individuals can be high or low.
• Has some definite advantages over straightbreeding.
Source: Steve Hammock, Texas A&M University Beef Cattle Shortcourse 2008
Look at your records to see what improvements you need to make in the herd. Also look at where and how your calf crop is marketed. For example, if you plan to sell off your calf crop, you may need to look at a terminal sire with higher EPDs in growth, weaning weights and carcass traits. If, however, you are raising your own replacement heifers, the maternal traits will be more important.
"In any business, you have to ask, ‘What will make an economic difference for me and my customers?'" says Michael Tess, animal scientist at Montana State University. That requires measuring and recording as much information about your herd as possible.
"At least get herd performance data," Tess says. This way, you can track performance over time and measure if genetic selection choices and matings have hurt or helped your herd.
Then you need to decide if you're going to straight breed or crossbreed your cattle. For many commercial producers, crossbreeding systems increase heterosis, or hybrid vigor.
Stephen Hammack, Texas Agri-Life Extension beef cattle specialist emeritus, says that to understand the real benefit, you should keep in mind that heterosis is highest in reproductive and fitness traits (such as fertility, age at puberty, livability, longevity); medium in production traits (birth weight, weight gain, mature size, milk yield); and lowest in carcass traits (marbling, leanness and tenderness).
Choose a system. From there, you want to choose a mating system that will help you achieve your goals. "When you decide on a breeding system, it needs to be sustainable," Marston advises. Too many times, producers get into a situation where they start a breeding system but run out of resources and animals to sustain it.
"It is critical to understand the pluses and minuses of breeding systems and decide on one before choosing breeds or selecting individuals within breeds," Hammack says.
There are two basic breeding systems, he explains. "If the source of replacement females is heifers produced in the herd, there is a continuous system. If heifers are not put back in the herd, there is a terminal system. Differences in these systems must be well understood, or serious mistakes can be made."
In continuous systems, there are different options as well. A true rotation option uses two or more breeds and the same number of breeding groups, Hammack says. The simplest rotation is a two-breed cross, sometimes called a crisscross. A different breed of sire is used continually in each of the two breeding groups. Replacement heifers are moved or rotated for breeding from the group where they were produced to the other group, where they will remain for their lifetime. This method, however, can be complicated and difficult to maintain depending on a producer's herd size and management system.
|This table compares breeding systems at the cow–calf level using a simple measure of production efficiency: pounds of calf weaned per cow exposed to breeding.
Another option is sire rotations, which are sometimes called rotations in time. "Instead of rotating the females among multiple breeding groups as in true rotations, sire breeds are changed periodically in a single breeding group," Hammack says.
Within these systems, you then decide if you want to straight breed or crossbreed. In a crossbreeding system, unless you have a herd of 300 or more cows, there are really only two choices that are sustainable, Tess says. One is a simple rotation system using two or three pastures. The other is using F1s or composite bulls and one or two breeding pastures.
At this point, you need to determine the breed that will help you achieve your goals, and then select individual bulls based on the criteria you developed and the system you have in place. Then be consistent and stay focused on the end point.
Hammack offers tips on selecting a simple mating system: If heifers are saved, all genetic features of both sires and dams are relevant. But in a terminal system where heifers are not saved, maternal traits of sires can be ignored. Of course, maternal traits are important in the source of replacement females for a terminal system.
Evaluate the program. Make sure your system works in your operation. "Producers get so tied up in genetic systems, they forget to see if those animals fit the environment," Hammack says.
To help determine if your cows are fitting their environment, look at:
- pregnancy rates;
- calving distribution;
- body condition scores;
- weights at different marketing opportunities.
For instance, no amount of genetic selection will help a herd if the bull you have chosen causes pregnancy rates to decline, or if the heifers and cowherd become so large or high-milking that the environment cannot sustain them.
"When you notice declines in these areas, then either your management has changed or the genetics are not balanced," Marston says. BT
A Wealth of Experience
The iconic King Ranch serves as a great example of customizing a breeding program. The ranch has 1,000 head of Santa Gertrudis in the purebred herd, which provides seedstock for the commercial herd of 24,000 head of Santa Cruz—a composite of Santa Gertrudis, Red Angus and Gelbvieh. Very few of the bulls are sold publicly.
|Scott Moore, King Ranch cattle area manager, says a customized breeding program and selection system is helping the ranch achieve its goal to differentiate its end product.
"We have a breeding system where the purebred herd is divided into six herds," explains Scott Moore, King Ranch cattle area manager. To prevent inbreeding, replacement heifers go back into the birth herd. Bulls can move into the five other herds, just not back into the birth herd. DNA fingerprinting is used to identify sires of calves.
"For us, DNA started as a way to identify single sires. Our pastures just don't work for small breeding groups," Moore says. "Now we've evolved to use DNA to select for marbling, tenderness and feed efficiency. It allows us to account for variability of the animal."
Each year, the ranch conducts an economic analysis on each herd to determine direction in marketing and breeding. That step provides a direction or goal to achieve. To measure and track those goals, the ranch developed a calf value index based on ranch-specific weighted economic values. The index has taken 10 years to develop and is a combination of genetic and phenotypic traits. Ultrasound data was used to develop an in-herd EPD system, which was combined with phenotypic traits to create the calf value index. That value helps the ranch determine which bulls to use with which herds.
DNA technology—in particular, Igenity—is used to identify tenderness, marbling and feed efficiency, traits that are difficult to measure phenotypically.
"To speed up genetic improvement, bulls are rarely used more than two years," Moore says. But first, females have to produce a calf. Non-reproductive cows get culled.
"Ultimately, our goal is to differentiate our product through marbling, tenderness and feed efficiency," Moore says.
To contact Kim Watson, e-mail firstname.lastname@example.org.
- January 2009