Bull Selection – Using Economically Relevant Traits

Sire selection often encompass a variety of factors such as how well a bull fits into the breeding objectives of your operation, breed, conformation, pedigree, birthweight, and price. Recent surveys from western Canada in 2014 and 2017, Ontario in 2015/16, northern Ontario and Quebec in 2015/16, and Atlantic Canada in 2016/17 production years asked respondents to rank their top bull selection criteria.  There wasn’t a lot of variation between regions with breed, conformation, pedigree, birth weight, individual performance, expected progeny differences (EPDs), and temperament all being highly ranked by survey participants.   

Some of the criteria, like breed, may influence sire selection due to the desire to capture heterosis or breed complementarity effects.  Conformation is important for longevity and ensuring the bull gets the job done during the breeding season.  Having a bull with a desirable temperament makes everyone’s lives easier, especially if there are children or older individuals involved in the operation.  Individual performance and birth weight may give some indication of how the bull’s progeny may perform, but a better indicator in this area is actually the bull’s EPDs. Response to selection using EPDs is 7-9 times more effective than selecting based on individual animal performance⁷.

The question is, how well do these various selection criteria translate into profit?

Answering this question means taking a look at your operation.

• What are your breeding/marketing goals?
• Which traits affect the profitability of your operation?
• What constraints does your operation have (forage resources, labour, etc.)?
• Do you raise your own replacements or purchase them⁴?

Once those questions are answered, there are likely a number of traits you have identified as important to your operation.

While a number of data sources exist to help you evaluate the contribution of a potential herd sire to improving the traits of interest, it is important to recognize whether the traits you have identified are indicator or economically relevant traits.  Good record keeping is crucial to determine whether or not progress is being made in the traits you have identified as important to your operation’s productivity and profitability.

Economically relevant traits (ERTs) are those that are directly associated with a source of revenue, or a cost.  Not all EPDs represent ERTs – instead they use a related (or indicator) trait to estimate the ERT.

One of the best examples is birth weight.  Decreasing a bull’s birth weight by 5 lbs does not have any associated income or costs, but is often used as a bull buying criteria in an effort to reduce calving problems.

The actual ERT in this case is calving ease, as an increase in calving problems will reduce calf survival (less calves to sell), incurs higher labour costs (pulling calves, or more time spent monitoring), and delays cow rebreeding (younger and lighter calves to sell next year).

Similarly, ultrasound for carcass traits is another suite of common indicator traits, while the ERTs are the actual carcass measurements (weight, yield, and marbling).

We all recognize fertility (in both sires and dams) as a trait that has the biggest impacts on profitability.  But fertility has relatively low heritability, meaning that cumulative environmental influences (e.g. nutrition, weather, etc.) generally have a larger impact than genetics.  In Canada, some genetic evaluations do not report any EPDs at all for ERTs related to female fertility. While most evaluations include scrotal circumference (indicator), it actually has a near zero relationship with heifer pregnancy rate (ERT)

In the Canadian context, a stayablity or length of productive life type of EPD (probability of an animal remaining in the herd for X period of time or awarding more credit to cows remaining longer in the herd), while an ERT itself, is also the best proxy for fertility given the lack of EPDs in this area, as the most common reason for a cow to be culled is because she’s open.

When EPDs for both indicator and ERTs for the same trait are included in genetic evaluations (e.g. calving ease and birth weight), make sure you focus on the EPD for the ERT and not the indicator trait. The indicator trait cannot add more information to the selection process, as it is already used in the calculation of the EPD for the ERT in the first place.  When an EPD for an indicator trait is available, but no EPD exists for the ERT (e.g. scrotal circumference and heifer pregnancy rate), it can result in an over or under-estimation of the ability of the indicator trait to predict the ERT³.

Given the plethora of EPDs available, trying to sort through ten or fifteen or twenty individual EPDs that may not have relevance to your particular operation can easily lead to information overload.  By focusing on the ERTs, you can eliminate those bits of information that will not directly impact your operation’s profitability.

For example, if you’re using a terminal system (not keeping replacements) and selling at weaning, the weaning weight EPD is going to be one of your most important ERTs.  If you tend to retain ownership through to slaughter, the more relevant ERTs are carcass weight, quality, and yield grades.

In some cases, whether a published EPD is an indicator or ERT will depend on how that EPD is reported.  For example, carcass trait EPDs calculated using combination of ultrasound and actual carcass data would be ERTs (e.g. marbling score), but those reported on an ultrasound data basis (e.g. percent intramuscular fat) would be indicators.  Table 1 contains some common traits that may or may not have a published EPD in your breed of choice and whether they are an indicator or ERT.

Table 1.  List of selected EPDs characterized as indicator or ERT

Adapted from (4) and (6) (see references below).  This is not an exhaustive list.

Many genetic evaluations offer selection indices in addition to individual EPDs.  These are calculated by placing an economic weighting on individual EPDs to create a multi-trait selection model for different types of broad production systems (generally maternal or terminal).  These provide a way to objectively categorize a set of animals using the same criteria throughout.  Examples include the Canadian Simmental Association’s All Purpose Index (API) and Terminal Index (TI), AgSight’s BIO$ Economic Index, or the Canadian Hereford Association’s Maternal Productivity Index (MPI) and Feedlot Merit Index (FPI).  The indices offered by most breed associations are fairly robust across production environments, keeping in mind their overall objective – don’t expect high ranking terminal index bulls to give you stellar replacement heifers.

Ideally, selection indices would be tailored to each individual operation’s identified ERTs, with different economic weightings depending on the production system, but the creation of customized selection indices with real-world economic weightings requires detailed cost and return information and a complete understanding of the complex genetic relationships between traits.  This type of model may also present some difficulty for seedstock producers, as marketing based on a fluid index (where a bull could be in the top 1% for X trait in one type of production system, but only in the top 50% for the same trait in another production system) would be challenging.⁴

Regardless, the amount of detailed information required to populate these types of models may not be readily available for the average producer.

By identifying ERTs, you can narrow your selection focus to the EPDs that matter most for your breeding goals, increasing the likelihood that the decisions you make will actually have an impact on your bottom line.

Editor’s note: Stay tuned for part four in this four-part series. (See part one and part two).

¹Ahlberg, C.M., L.A. Kuehn, R.M. Thallman, S.D. Kachman, and M.L. Spangler. 2014. Genetic parameter estimates for calving difficulty and birth weight in a multi-breed population. In Proc. 10th World Congress on Genetics Applied to Livestock Production.

²Bennett, G. L., and K. E. Gregory. 2001. Genetic (co)variances for calving difficulty score in composite and parental populations of beef cattle: I. Calving difficulty score, birth weight, weaning weight, and postweaning gain. J. Anim. Sci. 79:45-51.

³Golden, B.L., D.J. Garrick, S. Newman, and R.M. Enns. 2000. Economically Relevant Traits: A framework for the next generation of EPDs. Proceedings of the 32nd
Research Symposium and Annual Meeting of the Beef Improvement Federation. Pp. 2-13

⁴Spangler, M.L. 2015.  Economically relevant traits and selection indices.  Range Beef Cow Symposium XXIV.

⁵Spangler, M.L. 2017.  Economically relevant traits.  Accessed Online at: https://beef.unl.edu/economically-relevant-traits

⁶Enns, R.M. 2010.  National Beef Cattle Evaluation Consortium Beef Sire Selection Manual 2^nd Ed.  The Role of Economically Relevant and Indicator Traits.

⁷Spangler, M.L. and R.L. Weaber. 2017. Genetic Selection vs. Visual Appraisal: Is it a Conundrum?  Range Beef Cow Symposium XXV

Don’t rock the boat while breeding heifers

Original article by S.L. Lake, R. Arias, P. Gunn, and G.A. Bridges, from 2013 Range Beef Cow Symposium
Nutrition During the 21 Days Post Breeding: Maternal recognition of pregnancy takes place around day15-17 post-insemination and that transporting animals near this time compromises conception. However, moving heifers within the first 5 days post-insemination does not cause this reduction. Although, research suggests that conception rates are compromised when heifers are placed on early growth pasture forages. Researchers hypothesized that feeding this high moisture pasture forage at turnout is limiting dry matter intake which in turn causes a temporary energy deficiency that results in temporary heifer weight loss during the critical stages of early embryonic development and maternal recognition of pregnancy. Therefore, it is beneficial to ensure heifers maintain the same plane of nutrition after breeding, at least until day 25 when the embryo should be completely attached to the uterus. If this is true, maintaining a positive plane of nutrition on heifers after breeding will increase 1st service conception rates, improving herd fertility and longevity.
Some spring-born heifers are developed from weaning to breeding in a dry-lot pens. Estrous synchronization and AI may be conducted while in the dry-lot to take advantage of proximity to corral/breeding facilities. Following AI, heifers are may be moved to pastures to expose them to clean-up bulls. The researches hypnotized (Lake et al. 2013) this shift in diet quality and quantity of nutrients, may negatively impact metabolism, body weight gains, and ultimately reproductive efficiency.
Investigators at Purdue University and the University of Wyoming jointly examined the role of post-insemination nutrition on AI pregnancy rates in beef t two locations (Purdue; n = 53, Wyoming; n = 99) heifers were fed at 125% of NRC maintenance requirements (approximate ADG of 1.5 lbs/d) from weaning until estrous synchronization and AI. Immediately following estrous synchronization and AI, feed delivery to heifers was tightly controlled as heifers were specifically fed diets formulated to:
1) 125% of maintenance requirements
2) 100% of maintenance requirements
or 3) 80% of maintenance requirements
Heifers remained on these diets for 21 days following AI. Heifers that returned to estrus during the 21-day dietary treatment were inseminated and following the conclusion of the dietary treatment all heifers were comingled and placed with fertile bulls. Pregnancy diagnosis was conducted at 30 days post-AI to determine pregnancy success following the initial AI and 30 days after the breeding season to determine 2nd service AI pregnancy rates and overall breeding season pregnancy rates.
Analyses revealed that heifers that were fed to continue their pre-breeding plane of nutrition (125% maintenance) for 21 days post-AI had greater (P = 0.04) AI pregnancy rates compared to both groups of heifers that had a decrease in dietary plane of nutrition (100% maintenance and 80% maintenance). In addition, heifers in the 100% NRC and 80% treatments had decreased (P < 0.05) 2nd service AI pregnancy rates and decreased (P < 0.05) overall breeding season pregnancy rates. If heifers are transitioned to pasture immediately following AI are supplemented with a concentrated feedstuff such as distillers grains to prevent post-AI weight loss, pregnancy rates are not negatively impacted.
Embryo Quality: It was hypothesized that day 6 embryos collected from heifers that were fed restricted, sub-maintenance diets would have poor embryo quality. This study was conducted at the University of Minnesota and South Dakota State University (SDSU). All heifers were on a common diet during development. Estrus was synchronized and timed-AI was conducted. On the day of AI, heifers were placed in one of two nutritional treatments:
At UMN
1) 120% maintenance requirements
2) 80% maintenance requirements
At SDSU
1) 125% maintenance requirements
2) 50% maintenance requirements
Dietary treatments were fed until embryo collection was done using non-surgical embryo flush techniques six days after AI. Recovered embryos were microscopically evaluated and graded on a 1 to 5 scale (1 = excellent, 2 = good, 3 = fair, 4 = poor, and 5 = degenerate) to evaluate embryo quality.
Results across both locations were combined to illustrate the effects of nutrient restriction on early embryonic development. Nutrient restriction immediately following AI resulted in poorer quality embryos that were developmentally retarded as indicated by being at an earlier stage of development and having fewer total blastomeres In addition, embryos from nutrient restricted heifers had a decreased (P = 0.01) percentage of live blastomeres.
These results suggest that the early embryo, oviduct, and uterus are sensitive to immediate changes in nutrition. Nutritional inputs to reproducing beef cows must be managed to allow for the animal to be in a positive energy balance. However the researchers indicated caution is warranted as over-nutrition may also compromise various reproductive parameters.
Source: Ohio Beef Cattle Letter

Breeding replacement heifers

I know some of you have been calving, in many cases first calf heifers, during this terrible cold and snowy weather. I realize that cattlemen have had a tremendous work load and stress during this time as the cold east winds just wouldn’t relinquish its grip and unless the new born calves were not attended to immediately some would chill to the point that they couldn’t stand and nurse on their own. I know some have experienced loss but if only those that are critical of us in the cattle business only knew the effort that is put forth to save every calf it would boggle their mind. We not only do it because it is our livelihood but more important we do it because we care deeply concerned about our livestock and their welfare.

Almost every publication and news report talks about the price or value of our cattle and often addresses the topic of rebuilding the cow herd in the United States. Even we have a lot of positive signs to rebuild we still have several parts of the United States that are experiencing drought and in some cases severe snow storms and therefore it appears the rebuilding of the cattle herd may be modest at best. This makes it even more attractive down the road if we have the resources to grow our own cow herd now. We do see considerable more interest in this region retaining and developing replacement heifers. Calls and watching the price of high quality bangs vaccinated heifers tells me we will see considerable rebuilding in this area.

Most decisions have been made on the feeding and management program to develop the heifers, however some time remains for tweaking the system. Obviously if the heifers have not been gaining enough there is still time to catch them up to a desired target weight for breeding For years it was routinely recommended to develop the heifers to achieve 65 percent of their expected mature weight at breeding time or if a heifer that was expected to mature to 1,300 pounds then she should weigh at least 845 pounds to assure good reproduction. Some still make that recommendation which does assure good reproductive performance however research now shows that this often results in a more expensive program than is needed. Ten to 12 years ago Dr. Gene Duetcher now retired from the University of Nebraska West Central Research and Extension Center challenged the 65 percent recommendation and developed some heifers to be bred near 50 percent of their mature weight or close to 200 pounds lighter. Their data found the heifers had very acceptable breeding performance and were developed with much less cost. This work has been followed up by Dr. Rick Funston reproductive specialist, University of Nebraska West Central Research and Extension Center and he writes and speaks on this concept frequently. Dr. Funston states that costs can be cut to least $100 per heifer without sacrificing reproduction plus any open heifer can be sold at a lower breakeven.

The question often arises as the most desirable way to breed heifers. By far the majority of first calf heifers are naturally mated however with innovation and lower labor synchronization programs many producers do use AI (Artificial Insemination) in conjunction with synchronization.

Natural mating is still a viable option especially with increased technology to give more accurate ESDs (Estimated Progeny Differences) for calving ease plus other traits. We see far fewer “wrecks” today than in the past when at times hide color and/or breed seemed to be the major criteria for selecting bulls for breeding heifers. As a result of more attention focusing on EPDs to predict calving ease considerably less heifers are assisted at birth and certainly fewer C-sections.

There are still some major advantages of using proven sires for first calf heifers plus often we can also look at growth traits with accuracy and perhaps maternal and carcass weights. I have felt for years that proven bulls that excel in calving ease and maternal traits are excellent candidates for next year’s replacements. They are often the oldest heifers that are born in the first cycle of calving. Currently with sexed semen perhaps we even have greater opportunities to use this as a source of replacement heifers.

AI is much more feasible today with the use of synchronization programs that allow timed AI. Breed them on a break or week-end when the kids are home from college. One can also hire a nomadic crew that comes through on a given schedule; perhaps all you need to do it keep books when they are being bred. It seems that it is never that simple but fun to think that way. Currently there are many options available that allows a large percentage for the heifers to be bred to superior bulls in a short time period.

The two synchronizing programs that are very popular are the MGA – prostaglandin and the 7 day CIDR norgestmate (GnRH) program. Basically the oldest and perhaps the lowest cost is feeding MGA for 14 days and then giving a prostaglandin 19 days after the feeding of MGA. Breeding can then be done with heat detection or heat detection and breed for approximately 80 hours and then time breed anything not heat detected and give a shot of GnRH.

The 7 day CIDR works similar however the CIDR’s are taken out on day 7 and a prostaglandin is administered at that time of CIDR removal. The heifer can then be heat detected up to 80 hours or some simply breed every heifer between 72 – 84 hours and at the time of breeding each heifer is given an injection of GnRH. The MGH program requires initiation 33 days ahead of time to start breeding while the 7 day CIDR program can be done with less time of initiating the synchronization program. Sound complex and confusing? Help is available in many places. Almost all sire catalogs have these and variations of these programs published in their catalog. Need some help in planning? An excellent spreadsheet planning aid can be downloaded from Iowa States Beef Center web site www.iowabeefcenter.org/esterus_synch.html. All you have to do is put in the date you want to breed and select the program you want to utilize and it will fill in the dates to carry out each procedure. A reproduction web site www.beefrepro.unl.edu also has considerable information on breeding programs. Semen sales representatives and beef extension specialists will also be helpful resources. Best of luck as you make breeding decisions. Also as many go into calving take care and be safe in those low rest times.

Ivan G. Rush is a Professor Emeritus at the University of Nebraska.

Building Better Beef Replacement Heifers

Written by Dr. Jim White and Mike John
Thursday, 01 March 2012 20:40

Feed them right early and have them at breeding weight in time

The goal for selecting replacement heifers is simple—you want them to conceive, calve early in the calving season, provide adequate milk production and produce a calf every year. But much of what makes a good replacement heifer begins long before you begin to eye the keepers. Dam nutrition has distinct and long-term implications for replacement heifers.

Heifer development is influenced by how the cow carrying the heifer was fed prior to the heifer being born. While you are familiar with the challenges of calf vigor born to dams calving thin, you might not know about studies that show how appropriate protein supplementation to late-gestation cows has a lasting effect on heifers.

Work at the University of Nebraska looked at the effects of nutrition of dams on growth and reproductive performance of their heifer calves. One group of last-trimester cows got a pound of 40-percent protein supplement three times a week, the control group didn’t. In the study, cows were managed similarly during calving and breeding. The research lasted three years—long enough for researchers to get a good look at the effects of feeding an appropriate protein supplement to late-gestation cows. Results showed that supplementing cows with protein during late gestation made for heavier heifers at weaning and breeding. Moreover, the heifers from protein-supplemented dams had higher pregnancy rates and earlier calving dates.

Aside from successful nutrition during gestation, pre-weaning management of heifer calves influences lifetime productivity. Heifers should be programmed to calve early during their first calving season. They will tend to calve early and wean heavier calves throughout their lifetime. Poorly developed heifers will fail to conceive or will calve late the first year and wean lighter calves.

Many of the heifers that calve late will be open after a limited breeding season.
With that in mind, there are several goals to work toward when developing heifers. Hopefully they will: 1) reach puberty by 12 to 14 months of age; 2) achieve high percentage for conceiving early in the breeding season; 3) be structurally large enough to minimize dystocia.
Due to the record-high value of feeder heifers and the high cost of developing replacement heifers, it makes sense to pay attention to genetic factors when selecting and breeding replacement heifers.

As stated above, selecting potential replacements from heifers born early in the calving season will make it easier to assure that they do the same when they calve.
Along those lines, the cost of using proven AI sires can be justified in the immediate added value of offspring from the insemination. And, it will pay in other ways in the future. One way this practice proves its future value is that heifers that conceive to AI have proven their ability to conceive early under a process that often has a lower conception rate than natural service. Odds are high that she will continue to do so in future years. Plus, bull calves from the AI services should be heavier and have predictable performance based on high accuracy EPDs. There are also well-documented advantages for multi-generational “stacking” of those predictable traits in future replacement heifers.

Feeding Replacement Heifers

Develop a ration geared toward adequate growth, not fattening. Given typical weaning ages, medium-frame heifers need to gain about 1.5 pounds per head daily from weaning to breeding. Large-framed continental breeds and crosses need to gain more than 1.5 pounds daily. Puberty is a function of both age and weight, so rate of gain can vary during the development period. Just make sure heifers reach the desired weight and appropriate body composition before breeding time.

To ensure that all heifers reach these weights before breeding, feed them separately from the cow herd. If possible, sort according to size. Smaller heifers require a more nutrient-dense diet and a higher rate of intake to attain target weights in the same timeframe as larger heifers. Remember that feeding replacement heifers similarly to terminal heifers will push the replacements heavier than they need to be—a costly proposition these days. Moreover, heifers that gain too fast have a tendency to have lower lifetime productivity, another costly proposition.

To determine the average daily gain needed for a group of heifers, subtract their average weight from the desired weight at breeding, and then divide by the number of days of feeding before the start of the breeding season.

Most heifers need to gain 1 to 1.5 pounds per day during the feeding period. Nutrient requirements for growing heifers to gain at these rates are listed in the nearby at right. These requirements are based on neutral conditions. Housing and other environmental conditions drastically influence the energy requirement of the animals.

Many combinations of feeds can be used for growing heifers—as long as intake and nutrient composition are appropriate. If you have to allow for error, it is better to overfeed protein than to overfeed energy. Heifers need to be grown rapidly but not fattened, so better-than-average forage should be offered. If heifers are on stockpiled pastures, they should be fed at least four to five pounds of Trendsetter Developer per head daily to attain the recommended weight gains; two to four pounds per head per day is the lower end of the feeding rate. Often, the feeding program can be divided into one of four scenarios: 1) the operation has a forage base; 2) the operation also has grain storage; 3) the operation uses grain co-products; 4) the operation uses corn or sorghum silages to develop heifers.

Taking periodic measurements of animal weight and height are helpful in determining if heifers are growing at the proper rate. Some cycling, estrus activity should be observed in the heifers by six weeks prior to the breeding season. If you don’t see estrus activity six weeks or so prior, it’s likely that the heifers are smaller than they need to be. If that’s the case, you have roughly a month to get enough weight on them so they will be cycling at breeding. If the situation arises in which you need to put on weight on a deadline, feed Full Throttle or Cattle Charge at two percent of bodyweight per head per day along with free-choice forage.

Dr. Jim White is ruminant nutritionist for MFA Incorporated. Mike John is director of MFA’s Health Track program.

Data Affirm Heifers Bred at Lighter Body Weight

EVIDENCE continues piling up that shows heifers can be effectively bred at lighter weights.

Significant amounts of data to this effect have come from Nebraska, in particular, and now, another project at the U.S. Meat Animal Research Center in Clay Center, Neb., adds more fuel to this fire of change.

In recent history, animal scientists recommended feeding replacement heifers a diet to achieve 60% to 65% of mature body weight, or BW, by breeding at 14 months of age. This was based on research conducted during the late 1960s through the early 1980s.

However, research conducted over the past 10 years has found that feeding beef heifers to 50% to 55% of mature BW reduced body size and development costs without compromising pregnancy rate.

Recently published research from the U.S. MARC examined whether developing pre-pubertal heifers on less dietary energy and to a BW of 55% rather than 65% at 14 months of age would compromise ovarian development and reduce fertility.

These researchers used 60 head of 8-month-old Angus and MARC II heifers each year in a study replicated in 2009, 2010 and 2011. MARC II cattle are a stable composite of a quarter Angus, a quarter Hereford, a quarter Simmental and a quarter Gelbvieh.

In each year, heifers received either a low- or high-gain diet, fed to achieve an average daily gain of either 1 or 1.75 pounds per day from 8 to 15 months of age, including the first 21 days of the breeding period.

The low-gain diet consisted of 30% corn silage and 70% alfalfa haylage, which was 13% crude protein and 61.6% total digestible nutrient. The high-gain diet was 69% corn silage and 31% high-moisture corn, which was 11.8% crude protein and 74.4% TDN.

Then they were transferred to pasture. At 14 months of age, the heifers were exposed to bulls for 47 days.

Average daily gain during the treatment period was 1.74 pounds per day for the high-gain heifers, compared with 1.04 pounds per day for the low-gain heifers. The high-gain heifers were 16% heavier than the low-gain heifers at the onset of the breeding period (926 vs. 798 pounds). They were 12% heavier at the end of the 47-day breeding period (921 vs. 824 pounds).

In 2010 and 2011, 97.2% of all the heifers were cycling by 21 days of breeding. Postweaning ovarian development was not compromised by treatment.

Researchers said a greater proportion of the high-gain heifers, compared with the low-gain heifers, conceived within the first 21 days of the breeding period. The actual numbers were 64.4% vs. 49.2%. Yet overall pregnancy rate was not affected by treatment. Those actual numbers were 83.0% vs. 77.7%, respectively. This was not statistically different.

The researchers concluded that the results from this study agree with previous similar studies. They said development of replacement beef heifers on less energy and at a smaller average daily gain from 8 months of age to achieve 55% of their mature BW at breeding may enable beef producers to reduce associated feed costs without compromising ovarian development or the proportion of heifers pregnant during a 45-day breeding period.

However, they noted that the smaller proportion of low-gain heifers becoming pregnant within the first 21 days of the breeding period may compromise their stayability in the herd as a result of calving and breeding later in subsequent years. This would be especially so if a greater restriction in body weight gain was imposed during the postweaning period.