Resolve to use science-based tools to select bulls.
By Matt Spangler
The topic of sire selection is popular this time of year, and it seems that annual reminders of the importance of developing breeding objectives, identifying economically relevant traits, and using EPD are common. Expected progeny differences have been around for close to 50 years, so it is nearly impossible for any reader to have avoided hearing about them at some point. Yet, survey results conducted by both academics and by popular press publications suggest that EPD do not serve as the primary selection criterion used by commercial producers.
This is a critical failure on multiple fronts, and begs the question if a known and validated tool is to be ignored can the US beef industry reasonably argue that it is on the path towards sustainability. Understanding the statistical models that are beneath the calculation of EPD are not required to use EPD any more than knowledge of thermal dynamics are needed to use your lawn mower. However, in both cases (selecting bulls and mowing your yard) knowledge of how to use the right tool for the job is important.
(Brief) HistoryTo my knowledge the first Estimated Breeding Values (EBV; twice an EPD) in beef cattle were published in a Charolais bull sale catalog. Litton Charolais had worked with Dr. Richard Willham from Iowa State University and were obviously early adopters of this technology. The American Simmental Association published the first sire summary in 1971, and analysis conducted at Boeing given the computational requirements needed. The same analysis today could likely be completed on a standard laptop.
Throughout the remainder of the 1970s and early 1980s numerous other breed associations followed suit. Importantly, the Beef Improvement Federation (BIF) was formed in 1968 as a vehicle for industry and the research and extension communities to identify and address emerging questions related to beef cattle genetic improvement. This organization holds an annual symposium and provides a set of guidelines for the recording, reporting, and utilization of performance data in beef cattle.
Although the science underpinning genetic evaluations have changed substantially since the 1970s, the fundamentals from a practitioner’s (cattle breeders) perspective have remained amazingly similar: Define a breeding objective, select breeds to utilize in a breeding system, and select individuals (bulls) based on the most reliable source of data possible.
Setting goalsI suspect that nearly everyone does this, if even informally. In the field of animal breeding and genetics this exercise is called developing a breeding objective. At a high-level a breeding objective identifies and few fundamental plans, including: how replacement females will be obtained, when calves will be sold and how calves will be sold. From simply developing plans that answer these three questions, producers can identify a list of traits that are economically relevant to their breeding objective.
Economically relevant traits (ERT) are those that are directly tied to a source of revenue or a source of cost. In example, weaning weight would be economically relevant for someone that sells calves at weaning given their revenue is related to the weight of calves when they sell them. Similarly, carcass weight would be an ERT for someone that retains ownership and sells cattle ‘in the beef.’ For someone that purchases replacement females, maternal traits are not important when selecting bulls. However, if replacement females will be kept, then traits like mature cow weight, maternal weaning weight (milk), stay-ability (sustained cow fertility) become important.
Breeding objectives can be layered with additional detail once the high-level plans outlined above are known. This additional detail could include current levels of performance of the cowherd and calves produced. In example, if a producer knows that their cattle grade low choice (on average), then there is economic incentive to increase marbling score to improve quality grade. If the same producer has a 0% incidence of dystocia in heifers, then there is little economic incentive to continually select for improved calving ease, instead emphasis should be on maintaining current levels.
Finally, constraints on the system, such as availability of labor, land, forage, can be identified as a means of determining how an individual enterprise’s costs might differ from that of other entities. Breeding objectives can vary from those that are exceptionally detailed to those that simply state core objectives. Regardless, have a breeding objective (and sticking to it) will help ensure that breed selection, breeding system design, and ultimately bull selection decisions will improve profitability.
Choosing breedsBreed choice is often steeped in tradition and sometimes a result of having succumbed to popular trends. It’s important to match breeds to the breeding objective. All breeds have strengths and areas of weakness, and there is not a single breed that excels in all areas that lead to improved profitability.
To compare breeds based on how contemporary genetics perform, use the most current U.S. Meat Animal Research Center ‘Breed of Sire Means’ table. This resource compares the performance of offspring from registered sires of several breeds when used on crossbred cows. Given this compares the impact of the breed of sire, it would be interpreted as half of the breed difference.
Breeding systemsOnce breeds have been chosen, a system that combines them is needed. Crossbreeding, which is an essential tool for commercial cattle producers, requires a plan. There are a multitude of breeding systems to choose from ranging from simple terminal systems to more complex multi-breed rotational systems. The choice of a breeding system essentially boils down to the need to produce replacements, the ability to utilize multiple breeding pastures, and a long-term plan to ensure the system is maintainable. A thorough review of different crossbreeding systems is available in the Beef Sire Selection Manual.
Advances in reproductive technology, including the use of sexed-semen, offers a potential new way to implement advanced breeding systems without the need for natural service sires of multiple breed types.
Although using artificial insemination (AI) may seem daunting for many commercial cattle producers, a careful economic analysis is required before passing judgment on the feasibility of an AI program. The ability to reduce genetic lag by having direct access to “elite” genetics is one benefit. With the use of sexed semen, the ability to reduce the frequency of the non-desired sex (i.e., females for a terminal herd) is another benefit.
Selecting bullsOnly before the steps mentioned above are considered is it time to actually select bulls. Bulls (either semen or natural service sires) must improve profitability of the enterprise. To do so, they must improve economically relevant traits (defined in the breeding objective) such that greater emphasis is placed on objectively identified weakness of the cow herd and recent calf crop.
This also means that the bulls/semen must pay for themselves. In other words, if the bull that best matches the breeding objective costs $2,000 more than the bull that is second on the list, he must return at least $2,000 more through his offspring. If he cannot, he actually takes the enterprise backwards relative to improving profitability. This is not a “green light” to go out and buy the cheapest bulls possible, but it is a cautionary note to think about buying bulls as an investment in genetics and to consider the return on the investment.
Like other business decisions, it’s important to do business with an entity/person you trust and who provides superior customer service. Buying bulls/semen should be no different. Going to bull sales, to some people, is fun. However, you should feel comfortable enough with your seedstock vendor to simply give them an order. A good seedstock supplier should ask you questions about your operation and needs/goals before ever recommending bulls to you and they should treat your money like it was theirs. Accidents with bulls do happen—breeding injury, seemingly calm bulls have a bad experience, and bulls who passed a BSE later fail or do not seem to have an interest in breeding. Make sure you understand the breeding season guarantee and contact your supplier as soon as any issue arises.
Actual bull selection can be as complicated as the buyer wants it to be. The reality is that most commercial producers buy bulls, at most, once a year. It is understandable that the plethora of data supplied in a bull sale catalog (or semen catalog) would be overwhelming. If the goal is to confuse bull buyers, we as a seedstock industry have perfected our craft. Between the actual weights, adjusted weights, ratios, brief pedigree, EPD, indexes, pictures (with the all important footnotes), and in some cases the genomic scores and in-herd rating systems it can be confusing.
However, if bull buyers remind themselves that the goal is to improve the next generation of calves, and that a bull can only pass on a sample of his genetics (not the added feed, great clip job, etc.), the chore can actually become simpler.
If you are investing in genetics as a means of improving profitability then use the tools that are designed to do this—EPD and economic selection indexes. Expected progeny differences work—that is beyond contestation. Relative to growth traits, work from USMARC has shown that for every one unit change in sire EPD, the change in average offspring performance is approximately one unit—exactly what we would expect.
It’s important to be an educated consumer, meaning you should know something about breed average EPD. If you don’t, then ask. The last thing you want is buy a seemingly great terminal bull to later find out that he ranked in the bottom of the breed for growth and carcass traits.
The inclusion of genomic information into the EPD calculation also helps bull buyers ensure that what they are getting is what they wanted. Genomics increases the accuracy of EPD, translating into more confidence that the bull’s true genetic value is represented by their predicted genetic value (i.e., EPD).
There is still uncertainty in yearling bulls, because they simply have not had registered offspring to increase the accuracy of their EPD even more. However, genomics has gone a long way to increase accuracy. In example, genomically testing a non-parent bull increases his accuracy to the same level as if he’s already sired upwards of 10-20 calves for growth traits and over 15 calves for traits like stay-ability.
Multiple trait selectionThere are multiple traits that impact profitability, and thus selecting bulls requires contemplating multiple traits simultaneously. I suspect most people use what would be called Independent Culling Levels (ICL). An ICL is the process of setting thresholds that a bull must meet before he can be considered. Bulls not meeting or exceeding the threshold for any trait is then removed from the candidate list.
This process is flawed for several reasons. The bull that misses one threshold, by only a small amount, might more than make up for the small deficiency by superiority in all other traits making him the most likely to increase profitability. The process of using ICL does not consider that not all traits are equally economically important.
The better method is to use economic selection indexes. The majority of beef breed associations offer at least one. These tools are an index of multiple EPD weighted by their economic value. It’s important to use indexes appropriately. Some are designed by terminal matings only (i.e., Angus $B) while other are designed for those that retain replacements and sell cull heifers and steers (i.e., Simmental API). Using the appropriate economic index can greatly simplify the sire selection decision making process.
For bull buyers, and bull sellers, that wish to develop more customizable economic indexes there are options. The Beef Improvement Federation offers a web-based decision support tool called iGENDEC . This software allows users to input their operational costs, pricing schedule for calves sold, current levels of phenotypic performance, breed composition of cows and other details that are unique to their enterprise. The result are weights for each trait in the customized index. Users that know more about the current performance of their herd (or their customers herds) will benefit more from using iGENDEC.
Concluding thoughtsBull buying season is upon us once again. This year, resolve to use science-based tools to select bulls. If a commercial producer is profit motivated, and I recognize that not all are, then it is hard to rationalize a breeding system that does not involve crossbreeding and a sire selection plan that does not use EPD and/or economic selection indexes.
Cattle breeding is a long-term process; the decisions we make today impact subsequent generations of family members who take over the family business. I would simply ask that we set the stage for the next generation of cattle producers to enable them to be successful — using science in a simplified form such as EPD and economic election indexes does that.
Additional resources eBEEF.orgSire Selection ManualNational Beef Cattle Evaluation ConsortiumBeef Improvement FederationUNL Beef Production
Spangler is a professor and beef genetics specialist with University of Nebraska-Lincoln.
