Sire selection questions answered as bull-buying season is in full swing

In a recent University of Nebraska-Lincoln (UNL) BeefWatch podcast, dated Feb. 14, UNL Beef Extension Educator Aaron Berger and UNL PhD Student Drew LaKamp discuss an article titled “Sire Selection FAQs” from the February UNL BeefWatch newsletter. 

As producers looking to attend bull sales receive bull catalogs, addressing a few frequently asked questions (FAQs) might prove helpful as producers consider what bulls to buy this spring and consider the tools they need to select them. 

Balancing maternal and terminal characteristics 

Some producers keep their own replacement heifers while also retaining ownership on cattle through the feedyard. One common question is how producers can keep cow weight down while simultaneously ensuring hot carcass weights don’t go down as well. 

LaKamp explains balancing maternal and terminal characteristics can be tricky. If producers want to keep replacement heifers, but don’t want to use multiple bulls or utilize artificial insemination, the best solution is to select a herd bull that optimizes mature weight and carcass weight. 

Many breeds have expected progeny differences (EPDs) for both of these traits, which makes it possible to select for both. 

In the article, LaKamp notes, ideally, this would be done using an economic index which assumes replacements will be kept and steers and culls will be sold. Combined indexes, such as the Combined Index Value ($C) for Angus or the All-Purpose Index (API) for Simmental, are designed to optimize maternal traits, such as mature body weight, with terminal traits, like carcass weight, to maximize profit. 

Wholesale purchasing 

Berger asks if there is an advantage to buying bulls at wholesale – for instance, buying three or four bulls born of the same sire. 

“Is there an advantage in terms of calf uniformity?” he asks. 

“The general idea is if two bulls are related, their offspring should be uniform in appearance, but it’s really hard to determine how closely related those two bulls are,” says LaKamp. “On average, they share about 25 percent of their genes, but a specific pair can share anywhere between zero to 50 percent.” 

He adds if a producer is using half-sibling bulls and are not sure of their genetics, it can be a big gamble to know whether they are getting the same genes or not. 

Berger notes a better strategy would be to select bulls with similar EPD profiles for traits in which uniformity is desired.  

“Similar EPD profiles are going to push producers in a more uniform direction, rather than using two bulls or half siblings,” he says. “Unless a producer does genetic testing to see how closely related the bulls are, there’s really no way of knowing.” 

Berger further notes a dam’s genetics can vary as well, so the best practice for uniformity among bull selection is by choosing bulls with similar EPD profiles. 

Understanding genomic information 

When looking at genomic information, such as genomic percentile ranks, EPDs, adjusted weights and ultrasound scans, the data doesn’t always agree.

The genomic percentile ranks tell a different story than the EPD, and the EPD indicates a different story than the scan data. A common question among producers is which one they should believe. 

LaKamp notes when it comes to making selection decisions, EPDs are the best tool. Every other source of data for a trait, such as adjusted phenotype, genomics, pedigree, etc., are already included in the calculation of an EPD. 

Phenotypes, such as weights and scans, are affected by both genetics and the environment, whereas, genomic profiles by themselves do not account for the bull’s own performance. 

Only EPDs bring all of those pieces together and appropriately weighs them, he notes. 

“The best tools are EPDs,” he says. “EPDs tie everything together, including the adjusted phenotype and genomics.” 

Calving ease and dystocia 

For many producers, calving ease is important, especially when breeding replacement heifers. LaKamp notes choosing bulls with a good calving-ease EPD is going to be the most effective option in this situation. 

The bull’s calving-ease direct EPD is an estimate of how easily a bull’s calves will be born when he is bred to heifers, whereas the calving-ease maternal EPD is an estimate of how easily a bull’s daughters will give birth when they have their first calf. 

LaKamp notes while it may be tempting to select on birth weight, as birth weight is an indicator of calving ease, it does not tell the whole story. 

Additionally, birth weight records are used to calculate calving-ease EPD, and selecting on both will not improve calving ease more than selecting on calving ease alone. 

“From a genetic standpoint, the best tool to improve calving ease is going to be the calving-ease EPD, either by looking at the direct calving-ease EPD or the maternal calving-ease EPD,” he says.

He adds, “Calving ease already includes birth weight, so selecting based on calving ease and birth weight together is kind of like double dipping. This may result in a low birth weight, which is going to impact the calf’s weaning, yearling and final weight, which ultimately might impact a producer’s revenue.” 

For many producers, calving ease is their number one priority. Therefore, LaKamp encourages them to look at other EPDs if dystocia or calving difficulty is not a concern in their herd. 

“I’m not saying calving ease isn’t an important trait, but if there is not a dystocia problem, calving ease doesn’t need to be a number one concern. And, a bull’s calving-ease EPD doesn’t necessarily need to be at the top of the list when picking a bull.” 

Scrotal
circumference selection 

Berger notes in the last 35 years, there has been a focus on selecting bulls with a larger scrotal circumference, with the belief they will be more productive in terms of being a breeder and because scrotal size is correlated to the age at which a bull’s daughters reach puberty. 

In fact, LaKamp shares there is evidence selection for larger scrotal size leads to progeny which reach puberty at an earlier age. 

However, for taurine breeds – cattle generally adapted to cooler climates – females reaching puberty early is not as concerning as it once was. 

Therefore, according to LaKamp, scrotal circumference is not a good indicator of female fertility and has little relationship with heifer pregnancy rate or sustained fertility. He mentions selecting on heifer pregnancy or stayability EPDs would yield much greater genetic gains in female fertility. 

In closing, LaKamp says, “Go out there and find a bull that works for a specific operation and take him home.” 

Brittany Gunn is the editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.