Beef production specialist explains genetic selection tools and EPDs in cattle
Dr. Shelby Rosasco is a University of Wyoming Extension beef production specialist. She received her bachelor’s degree in agricultural education with a focus on animal science from California State University-Fresno, and her master’s and PhD from New Mexico State University with an emphasis on the effects of pre- and post-breeding nutrition on performance and reproductive efficiency of heifers.
On Feb. 16 during WESTI Ag Days in Worland, Rosasco shared with producers how genetic selection tools can help with decision making and how to understand and utilize EPDs in selection for breeding.
Setting goals
Rosasco noted it’s important for producers to set goals for their operation when making decisions on what bull to buy.
“Producers need to know why they are picking a specific bull out. It’s not as simple as, “I want to pick out the top bull at the sale” or “I want these different performance traits,” she shared. “Setting a goal can help producers when looking at a bull sale catalog and making sire selection decisions.”
She encouraged producers to write down goals and set a timeline for those goals, because genetic selection takes time.
“Having a set goal can really help,” she said. “Producers don’t want to bounce from trait to trait – one year cattle are being selected on weaning weights, the next for calving needs, the year after selecting for carcass traits – it’s not moving forward in a general direction. These goals should be profitable and sustainable.”
Goals should also be consistent but flexible, she continued.
“Producers don’t want to bounce around from all of these different ideas from year to year because it really confuses our genetic selection moving forward over time,” she explained. “This certainly doesn’t mean not to add traits to goals or ignore certain opportunities, but be thinking of the traits which have the ability to impact the profitability of the enterprise.”
Genetic selection tools
For many producers, expected progeny differences (EPDs) are a common genetic selection tool.
“EPDs allows animals within a breed to be compared for their genetic potential to produce a specific trait,” Rosasco mentioned. “EPDs are recommended to be compared within a breed – it can be difficult to compare EPDs between an Angus bull to a Hereford bull, but across-breed adjustment factors can be utilized.”
“EPDs are really telling producers, this is the genetic potential this animal has to be passed on,” said Rosasco. “EPDs are the best estimate of how a bull’s or cow’s progeny will perform on average compared to another bull or cow.”
The phenotype of an animal is influenced by the genetics coming from the cow and bull, as well as the environment the animal is raised in. EPDs are parsing out some of the environmental impact and saying, this is what is to be expected of the calves from this animal from a genetic standpoint, she explained.
Raw measurements versus EPDs
When looking at a bull sale catalog and EPDs, producers can look at an animal’s actual birth weight, weaning weight and yearling weight in addition to the EPDs. She encourages producers to pay attention to a calf’s weaning and yearling weight, but producers can have a big impact on actual performance data based on how they feed those animals, so actual performance data should be used in addition to EPDs.
“With EPDs, this is just what the genetics say,” she noted. “Selection based on EPDs is five to nine times more accurate than selection based on actual animal performance.”
“Use all the tools in the toolbox,” she said. “Focus on EPDs in addition to performance traits – don’t focus on one or the other.”
When looking at a phenotype of an animal – what their actual performance is and how they actually look – what producers are really looking at is the combination of the animal’s genotype and what the environment is doing, she noted. When comparing bulls, producers should focus on the traits impacting their goals and the profitability of the operation.
Rosasco highly encourages producers to utilize breed registries when looking at descriptions of EPD traits.
“It’s important to understand what these traits are saying when comparing two bulls,” she said.
Across-breed EPDs and accuracy
The U.S. Meat Animal Research Center (USMARC) has developed a chart to evaluate different breed EPDs. Several adjustment factors can be used to determine specific traits between breeds.
“These adjustments can be really impactful when producers are making a decision on a bull,” she noted. “If you’re going to compare bulls of two breeds, use the adjustment factors – it’s simple math.”
When looking at EPDs, there is another number listed – it’s an accuracy number and this is meaningful – it’s going to tell producers roughly how accurate the EPDs are, she said.
“Each parent passes on a random half of its genes to the offspring,” she added. “High accuracy doesn’t necessarily mean uniformity – a high accuracy bull won’t always produce offspring with uniformity across all of its progeny – there is just more faith in the EPDs when producers are reading them.”
Most registries have accuracy charts which highlight associated possible change, which can be helpful when choosing bulls, she noted.
Weaning weights and traits
Rosasco noted when choosing bulls it can be easy to focus on bulls who produce heavier weaning or yearling weights.
“When selecting bulls, it depends on the trait the operation is looking for, it depends on the goal and environmental restraints. Producers also don’t want to push certain traits too far,” she explained. “When producers select for certain traits, other traits can be positively or negatively affected.”
Weaning and yearling weight are a good example of correlated traits which can be impacted and result in a heavier mature cow weight, if the producer is always choosing the highest weaning and yearling weight when selecting stock, mature cow weight will also be increasing, she explained.
“Producers need to stay within the bounds of what the environment can handle, and not unintentionally pick out traits impacting mature cow weight,” she said.
The Milk EPD is another important trait. A Milk EPD is what the cow is contributing to calf weaning weight, she noted.
Economic indexes can also help with multiple trait selection, she explained.
“With single trait selection, all of the other traits are not taken into account. With economic indexes, all of these traits are economically relevant and will allow producers to select multiple traits all at once,” Rosasco noted. “Most breeds have economic indexes and can be a great resource.”
“Set goals – it will help make well-informed decisions,” Rosasco shared. “At the end of the day, producers should use EPDs and economic indexes to their advantage, because it can really make a difference.”
Brittany Gunn is the editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.
