Traits to consider when buying a bull
Bull sale season is under way, and producers will have many opportunities to buy bulls from now through the end of May.
With all of the options – sale dates, breeders, cow families and sires – to choose from, the decision of which bull to buy may not come easily.
“The first step in bull buying is to determine your expectations of your bull,” said Carl Dahlen, North Dakota State University Extension Service beef cattle specialist. “Certainly, he needs to be fertile and get cows pregnant, but beyond that, each rancher has his or her own expectations of a bull. Some producers need a bull that will produce growthy calves that have maximum weight at the time of weaning, while some select bulls that will minimize calving problems. Still others want the highest quality carcass possible.”
However, selecting for just one trait can have consequences. For example, by continually selecting bulls for the heaviest yearling weight, producers inadvertently would increase the mature cow size in their herd if they consistently select replacement heifers from within the herd. In addition, the heaviest yearling weights may be associated with heavier birth weights, which could lead to calving difficulty.
The best way to select a bull is to decide on a combination of traits that best fits the needs of the cowherd. Once the herd’s needs are realized, the decision about which bull to purchase is much easier.
“Choosing the right bull involves both a physical evaluation of the bull and a review of the available genetic information,” said David Buchanan, an animal genetics professor in NDSU’s Animal Sciences Department. “When looking at bulls, producers need to review the structural correctness, frame size and muscling pattern, and see whether the bulls have an overall eye appeal that they want to have in their next calf crop. A breeding soundness examination is also important.”
The review of available genetic information can be difficult. Sale catalogs will list expected progeny differences (EPDs) for calving ease, birth weight, weaning weight, yearling weight, milk and scrotal circumference. In addition, EPDs are available for carcass traits including carcass weight, marbling, ribeye area and fat thickness.
“While EPDs are the best estimates we have of the genetic worth of a bull, they are often used incorrectly,” Dahlen said.
To be used appropriately, EPD values from one bull in the sale catalog need to be compared with those of another bull. A bull with a weaning weight EPD of plus-40 will not have calves that are 40 pounds heavier than the breed average.
They will, however, have calves that are 40 pounds heavier than a bull with a weaning weight EPD of 0.
All EPDs published are specific to a particular breed and should be used only for comparison of animals within that breed. Also, the breed average EPDs are quite different for any individual trait.
An Angus bull that has an EPD of plus-40 for weaning weight is much different within his breed than a Shorthorn bull with an EPD of plus-40. In this example, the Angus bull would be right at the breed average of plus-40, while the Shorthorn bull would greatly exceed the 14-pound average EPD for weaning weight.
Each breed association will have its breed average EPDs for spring 2011 available on its Web site or through its breed representatives. A listing of the breed average EPDs for 17 breeds reported by the U.S. Department of Agriculture is available at http://www.bifconference.com/bif2010/documents/10_kuehn_thallman.pdf.
In addition to EPDs, selection indexes are developed by combining several EPDs and placing weights on the EPDs according to their relative economic importance.
For example, $W is a selection index that represents economic return for calves sold at weaning. Traits included in this index (birth weight, weaning weight, maternal milk and mature cow size) contribute to the value of a weaned calf.
Other common indexes include feedlot value ($F), beef value ($B) and grid value ($G).
Some producers also are collecting and advertising carcass data from the bulls being sold. Ultrasound data includes traits for percentage of intramuscular fat (% IMF, an indication of marbling), back fat and ribeye area. The scan data for individual calves typically is available along with a ratio and EPD values for carcass traits. The best way to use this data is to look at the EPDs that the breed associations calculate from the scan session.
“If EPDs were not calculated, the next best use of the ultrasound data is to look at the ratio numbers for each trait,” Buchanan said. “The within-herd ratio for each trait adjusts the individual values for age of the animal and is listed as a percentage. For example, a bull with a ratio of 110 percent for a given trait is 10 percent greater than the age-adjusted average of the herd he originated from.”
Using the raw values for carcass traits can be difficult because of differences in age and contemporary grouping. While consignment sales may list the values of ribeye area or % IMF for the bulls being sold, the numbers are of little use when comparing bulls without proper within-herd comparisons.
“Remember that the bull you purchase today can have influence on your herd for years to come,” Dahlen said. “Choose wisely by using the information that is available to you.”
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