Paisley looks at using ultrasound to select replacement heifers
Buffalo – As ranchers select heifers to use as replacements each year, UW Extension Beef Specialist Steve Paisley says that carcass ultrasounds can be utilized to select heifers.
“In developing and selecting replacement heifers, there is a genetic component, as well as a management component,” Paisley comments. “We can impact the quality of the calf even before it is born, and developmental impacts begin in gestation.”
Some factors to include in selecting heifers include ribeye area, muscling, marbling and feed efficiency, among other traits.
Using ultrasound
Paisley notes that, as one of four certified ultrasound technicians in the state, he collects data on yearling bulls and heifers to be submitted to breed associations for expected progeny difference (EPD) data.
“That is how ultrasound has traditionally been used,” he says. “I also do chute-side ultrasound, and in commercial cattle, we can get readings instantly.”
Chute-side ultrasound is often used to determine when to send grass-fed beef to market and to look at feedlot traits.
“For most breeds, we only need to take two measurements,” Paisley explains. “We measure the ribeye area and backfat between the 12th and 13th rib, where the carcass is split.”
In measuring these traits, Paisley notes that genetic correlation is high on ultrasound data, and heritability is moderate.
Carcass implications
Ultrasounding can aid in estimating yield grade.
“Yield grade is an estimate of leanness of meat,” Paisley says. “We try to estimate the cut-ability of the carcass.”
Yield grade includes backfat thickness and intermuscular fat. When comparing two 1,400 pound animals, one of which has a 14-inch ribeye and the other with an 11.2-inch ribeye, receive very different yield grade scores.
“The 14-inch ribeye shows up as a yield grade three,” he explains. “The 11.2 square inch ribeye shows up as a yield grade four. On most grids, that animal would get a discount.”
“In some cases, we run into problems where lightly-muscled cattle have higher yield grades and receive discounts,” Paisley comments.
Marbling
Ultrasound also allows the technician to estimate the marbling in beef carcasses.
“We take a picture of the loin muscle between the 12th and 13th ribs,” Paisley explains. “The computer draws a rectangle and looks at algorithms, and it estimates intramuscular fat, or IMF. We are trying to estimate the marbling score with IMF.”
A four percent IMF is equivalent to a low-choice grade.
“Right now, about 60 percent of cattle grade choice or higher, and only seven percent grade prime or higher,” he explains. “We can use ultrasound as a way to evaluate replacement heifers based on grade.”
Genetic component
Paisley also added that some of the factors can be genetically tested.
For example, genetic tests for percent IMF are available, and IMF shows up in EPDs as %IMF.
“We can increase the marbling and fat on a high-rade diet, but there is a lot of genetics built in there,” Paisley says. “We can select for superior marbling.”
Marbling and muscling are also related, and Paisley noted that selection for more muscling may sacrifice marbling.
“A lot of these components are highly heritable,” Paisley says. “We can improve or increase marbling and reduce the potential of a small ribeye.”
Producer tool
Using the example of a set of heifers from Converse County, Paisley says, “After retaining his heifers, a producer quickly realized he had a lot of yield grade fours and fives, predominantly due to light muscling. We decided to ultrasound his replacement heifers prior to breeding.”
The producer removed the bottom 10 percent of heifers each year, using ribeye area as one selection criterion. By using a criterion of ribeye area above 1.1 square inches per hundred pounds of body weight for heifers, Paisley says the producer saw improvements.
“In 2010, the average ribeye area per 100 pounds of weight was 0.92, or less than one square inch,” Paisley says. “In 2013, with essentially the same herd, the herd average ribeye area per 100 pounds of weight was 1.07.”
“Ultrasound is just another tool to think about using,” Paisley adds.
Cautions
Paisley cautions producers against selecting for extremes.
“When we think about mature cows, we don’t want extremes, probably,” he says. “While we may want to improve our cow, we may not want to go to extremes.”
Carcass traits and expected progeny differences provide good information for producers, but Paisley also mentions that other criteria should be used in selections, as well.
Paisley comments, “We can make dramatic changes, if we use ultrasound and carcass traits in the right context.”
Paisley presented at the 2014 Heifer Development Symposium, sponsored by the University of Wyoming and the Wyoming Business Council.
Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at saige@wylr.net.
