Category: Crossbreeding

Comparing Cattle for Crossbreeding

Across-breed EPDs and the value of shared metrics

Imagine you want to buy a horse. But you’re a tall guy, so you want a tall horse. In your search, you find advertisements for two likely potentials. They both look like great ranch horses, but one is listed as 72 tall while the other is described as 132 tall.

If you chose based on those numbers alone, without knowing the measurement systems being used in each case, you would be short-changed if you chose the second horse because of its seemingly larger height number.

If you knew the measurement system each number was coming from—inches and centimeters, respectively—and knew how to convert those systems to make them comparable, it would be clear that the first horse is taller despite the seemingly lower number (72 in. versus 132 cm, a.k.a. 52 in.). If both horses were measured using the same system—let’s say, hands, making them 18 hands versus 13 hands—to begin with, it would make finding the taller horse even easier.

Expected progeny differences (EPDs) in the cattle world are a lot like our hypothetical tall horses problem. Most breeds’ EPDs are on different bases. An EPD basis is analogous to a measurement system; it’s the system in which their measurement numbers (i.e., EPDs) make sense. If you try to directly compare the weaning weight EPD on an Angus bull to the weaning weight EPD on a Hereford bull, for example, your success at getting a bull that meets your genetic goals will be about as successful as if you had chosen the second “tall” horse.

Bull Selection: What are you looking for?

Editor’s note: The following is part two of a four-part series that will help you to evaluate different breeding programs, which bulls are optimal for your herd, and how much they’re worth. (Seepart one).

Bull selection is one of the most important decisions for cow-calf producers, with implications for short- and long-term profitability of the operation. The choice of bull can be immediately seen in the subsequent calf crop.

If the operation retains heifers and/or bulls, the genetics in the selected bull will be passed down to subsequent generations. Introducing new genetics is a permanent change to the herd, compared to the temporary nature of supplements or management practices. As such, bull selection can be seen as a long-term investment into the operation.

Research in the area of beef cattle genetics has been growing significantly. There are opportunities to improve profitability through sire selection. However, with a multitude of traits, breed differences, operational goals, and management practices, bull selection is a complex decision.

There are a range of different beef operations in Canada, and there is no one type of bull that is optimal for all operations. Bull selection depends on many factors such as management style, calving season, labour availability, age when calves are marketed, heifer retention practices, and nutritional management.

Before selecting a bull, operational goals should be established and the management and breeding practices (see Part 1) that fit those goals determined.

For example, a full-time producer who observes the cattle multiple times a day may not prioritize calving ease in a bull as much as an operation with limited labour. A farm with limited forage resources may prefer smaller cattle that are more efficient at converting low quality forage.

To assist with making bull selection decisions, consistent record keeping on the herd will help identify areas of strength and weakness in the herd and guide you towards the type of genetic change you want to see. Once operational goals and breeding programs have been determined a producer can focus in on specific Expected Progeny Differences (EPDs) to guide their bull selection.

When selecting a bull, Expected Progeny Differences (EPDs) are a helpful tool to predict bull performance. EPDs are the estimation of an animal genetic merit. They are compared to a breed average (not zero) and cannot be compared across breed. An explanation of EPDs can be found here and in NBCEC (2010).

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Table 2. Expected Progeny Difference (EPD) indicators by category

Calving ease is a key trait that influences profitability. It is estimated the majority of calf loss is a result of dystocia (difficulty calving). Dystocia results in higher labor costs, decreased calf survival, and delayed rebreeding for the cow resulting in younger calves at weaning the following year.

The EPD for calving ease takes into account numerous factors including birth weight. Studies suggest birth weight is the most important factor for calving ease – a one pound increase in birth weight increases the probability of dystocia by two percent (Herring, 1996). Birthweight, while important for calving ease, isn’t always a direct correlation, for example a larger frame score cow should have no problem giving birth to a 95 lb calf; whereas, a smaller frame score cow might, especially if that calf has a bigger head and shoulders. However, shoulder width and pelvic areas alone have not been shown to be useful predictors in calving ease (NBCEC, 2010). Purely focusing on low birth weights when selecting bulls can be ill-advised. As low birth weight is genetically correlated with weaning and yearling weights, such a breeding program may lead to lower growth performance (Herring, 1996).

“Labour availability, a high proportion of heifers, calving on pasture, or a new producer with limited time and experience, calving ease should be prioritized”

To determine the significance of calving ease in bull selection, the goals and type of the operation should be taken into consideration. For example, if there is low labour availability, a high proportion of heifers, calving on pasture, or a new producer with limited time and experience, calving ease should be prioritized. On the flip side, an intensive operation focused on selling large calves may not find calving ease to be as important. Calving ease may also be an important trait if calving in late winter (i.e., February), as cold weather has been linked to larger calves and lower calf survivability (Hamilton, 2010).

Other traits of interest are milk production and bull fertility.

High milk production results in increased weaning weights. However, it raises energy requirements for cows even when they are not lactating. If the cow-calf operation has low forage availability, selecting for high milk production may lead to feed shortages and undernourished cattle. If running a terminal system and not retaining any heifers, the milk production trait becomes less relevant.

Bull fertility is linked to higher semen quality and quantity, as well as a lower age of puberty for his daughters.

As already mentioned, there are potential trade-offs between birth weight and performance. A low birth weight may increase calving ease, but it is correlated with lower weaning weight. However, there are many cases where a low birth weight is warranted; for example, when labour availability is limited or when breeding heifers. A low birth weight can be compensated for by selecting for higher milk production; however, as milk production increases, the nutrient requirement of cows will also increase, although it’s not a direct 1:1 relationship. Selection for superior growth can lead to calving difficulty and cows too large for the existing forage resources.

When calves are marketed also affects bull selection. If calves are sold at weaning, producers can focus on traits associated with a higher weaning weight, such as milk production and weaning weight EPD. When ownership is retained, weaning weight is less of a priority, and the focus may shift to traits such as yearling weight and carcass indicators (e.g., carcass weight, ribeye area, fat thickness, marbling). EPDs can help remove some of the guessing game when it comes to carcass quality as visual appraisal of muscling does not have a strong link to carcass quality.

Bull conformation directly affects longevity, and his structural soundness is passed along to the cow herd. Conformation can be evaluated through visual appraisal. Key factors to look for are the bull’s ability to walk easily without discomfort, the slope and angle to the joints of the legs, free from defects of the claws (e.g. toes that cross over each other or turn up), and joints free of swelling and inflammation. Healthy legs and feet are particularly important for extensive operations and large pastures, especially if there is rough terrain or multiple bulls in a breeding field.

When looking at body condition, the goal is to choose a bull with a moderate score. If the score is low, the bull’s performance is reduced as they lose weight during the breeding season. If the body condition score is too high, sperm quality and stamina are adversely affected.

Temperament is another consideration for bull selection. Bulls that are aggressive, nervous, or flighty may be undesirable due to safety concerns (e.g. older operators or young children) or damage to facilities. On the other hand, as temperament is moderately heritable, overly docile cows can pose an issue if calving on pasture where predation is a concern.

There is no one-size-fits-all solution or a bull that is best for all scenarios, as the right genetics depend on the individual operation. Key EPDs include:

  • maternal and fertility traits (e.g. calving ease, milk production, bull fertility),
  • trade-offs between performance and carcass quality traits,
  • conformation and structural soundness.

For example, labour availability during calving season and how closely females are monitored will determine the emphasis on calving ease and birth weight EPDs when selecting a bull. Or if marketing calves at weaning or retaining ownership will influence trade-off producers are willing to live with. Is the higher birth weight and time spent at calving worthwhile come sale day when you see that weaning weight?

There are many different types of bulls available, and effective sire selection requires an understanding of the characteristics of the available genetics as well as your own operation. Deliberate alignment of the bull’s genetics to your operational goals will contribute to enhanced revenue and reduced costs.

Beef Improvement Federation (BIF) resources https://beefimprovement.org/library-2/fact-sheets

Kuehn, L. and M. Thallman. 2018 Across-Breed EPD Table and Improvements. Beef Improvement Federation (BIF) https://beefimprovement.org/wp-content/uploads/2019/01/18_ABEPDpressreleaseandfactsheet.pdf

Schmid, K. EPDs: What do all those numbers mean?http://www.beefresearch.ca/blog/epds/

National Beef Cattle Evaluation Consortium (NBCEC). (2010). Beef Sire Selection Manual 2nd Edition. http://www.nbcec.org/producers/sire_selection/manual.pdf

Gosey, J.A. (1991). Crossbreeding Systems and The Theory Behind Composite Breedshttp://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1235&context=rangebeefcowsymp

Weaber, R.L. (2015). Crossbreeding Strategies: Including Terminal Vs. Maternal Crosseshttp://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1331&context=rangebeefcowsymp

Agriculture Victoria (2017). Breeds of Beef Cattle. http://agriculture.vic.gov.au/agriculture/livestock/beef/breeds/breeds-of-beef-cattle Accessed January 16, 2019.

Evans, J. and McPeake, C.A. Crossbreeding Beef Cattle I. http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Rendition-2051/unknown Accessed January 20, 2019.

Gaines, J. A., McClure, W. H., Vogt, D. W., Carter, R. C., & Kincaid, C. M. (1966). Heterosis from crosses among British breeds of beef cattle: Fertility and calf performance to weaning. Journal of Animal Science 25(1): 5-13.

Gosey, J.A. (1991). Crossbreeding Systems and The Theory Behind Composite Breeds. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1235&context=rangebeefcowsympAccessed January 20, 2019.

Gregory, K. E., Cundiff, L. V., Koch, R. M., Laster, D. B., & Smith, G. M. (1978). Heterosis and Breed Maternal and Transmitted Effects in Beef Cattle I. Preweaning Traits 1, 2, 3, 6, 7. Journal of Animal Science 47(5), 1031-1041.

Hamilton, T. (2010). Summer Calving Can Be Super! http://www.omafra.gov.on.ca/english/livestock/beef/facts/info_summer_calving.htm Accessed January 20, 2019.

Herring, W.O. 1996. Calving Difficulty in Beef Cattle: BIF Fact Sheet. https://extension2.missouri.edu/g2035 Accessed January 20, 2019.

Koger, M. (1980). Effective crossbreeding systems utilizing Zebu cattle. Journal of Animal Science 50:1215.

MacNeil, M. D. (2009). Invited review: Research contributions from seventy-five years of breeding Line 1 Hereford cattle at Miles City, Montana. Journal of Animal Science 87(8): 2489-2501.

National Beef Cattle Evaluation Consortium (NBCEC). (2010). Beef Sire Selection Manual 2nd Edition. http://www.nbcec.org/producers/sire_selection/manual.pdf Accessed January 20, 2019.

Northcutt, S.L., Buchanan, D.S., & Clutter, A.C. Inbreeding in Cattle. http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-1974/ANSI-3165web.pdfAccessed January 16, 2019.

Turner, J. W., Farthing, B. R., & Robertson, G. L. (1968). Heterosis in reproductive performance of beef cows. Journal of Animal Science 27(2): 336-338.

van der Westhuizen, B. (2016) Inbreeding vs Linebreeding. http://www.ngunicattle.info/Publications/Journals/2016/Inbreeding%20vs%20line-breeding.pdfAccessed January 20, 2019.

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Bull Selection Breeding Programs That Suit Operational Goals

Editor’s note: The following is part one of a four-part series that will help you to evaluate different breeding programs, which bulls are optimal for your herd, and how much they’re worth.

There are a range of different beef operations in Canada, and there is no one breeding program that is optimal for all operations. Breeding programs will be determined by operational goals and the management practices that fit those goals.

Here are some examples.

A producer that sells weaned calves at auction may choose a crossbreed program with high calving ease and a focus on performance gained from hybrid vigour; or they may prefer the uniformity of a purebred program with reputation premiums.

A producer that retains heifers and is looking for maternal replacements may be focused on maximizing the performance through inbreeding and outcrossing within a single breed; or they may develop FI crosses with higher reproductive performance and longevity.

These choices may be limited by the number of breeding fields available or the number a producer is willing to manage. There are a variety of breeding programs available, and effective sire selection requires an understanding of the characteristics of the available genetics as well as your own operation.

Each breed of cattle has distinct traits that allow them to excel in different geographical or management environments (Table 1). Depending on the goals of the operation, a sire can be chosen that has the potential to make positive changes for your operation in the areas you’ve identified for improvement.

Table 1. Comparison between beef cattle breeds in Canada (Adapted from Agriculture Victoria, 2017)

Indicators:
• E: Early, A: Average, L: Late
• S: Small, M: Medium, L: Large
• 1 = high/desirable; 5 = low/undesirable

Source: http://agriculture.vic.gov.au/agriculture/livestock/beef/breeds/breeds-of-beef-cattle

Also see Beef Improvement Federation’s across breed EPDs

Purebred

The advantage of the purebred or straight-bred approach of using only one breed is a homogeneous herd where cattle responses to environmental and nutritional factors are easier to predict. There will be consistency in nutritional needs, weaning, yearling, or finishing weights, and days on feed. The largest advantage is the ability to market a relatively uniform product, but ease of planning, and providing breeding stock forcommercial operations intending to maximize hybrid vigour may also be considerations.

When the parents have very similar genetics, the calf is more likely to have two sets of identical genes (homozygosity), which can have beneficial effects if the genes are associated with superior performance. However, negative traits can also show up with homozygosity. This can lead to the expression of abnormal traits, such as lethal recessives (e.g. curly calf syndrome, dwarfism, neuropathic hydrocephalus, etc.) It can also have more subtle effects on overall performance by increasing the amount “inbreeding depression” in the population.

Inbreeding depression is a reduction in performance due to the mating of highly related individuals, and it most negatively affects reproductive traits, followed by growth traits, but seems to have little effect on carcass traits. It is associated with an increased percent of open cows and stillbirths, with decreased levels of survival, growth, and overall performance (Northcutt et al). Generally, caution must be exercised when inbreeding as there is a high risk of performance reduction if the breeding program is not managed very carefully.

Three common purposes of inbreeding are to:

  • to test a bull for the presence of undesirable genetics that show up with inbreeding
  • develop inbred lines for a crossbreeding system
  • linebreed, or to maintain the genetic contribution of a genetically superior individual in the larger population

Linebreeding seeks to preserve and continually improve upon the genetics of a high performing ancestor. While linebreeding mates closely related individuals, it seeks to minimize the level of homozygosity (and thus inbreeding depression) while maintaining a high level of relationship to the high performing ancestor. Linebreeding is typically merited when there is difficulty finding outside bulls with sufficient performance to improve the herd.

Key components of a successful linebreeding program include:

  • individuals selected for a linebreeding program must be of superior quality with no genetic defects
  • meticulous record keeping of breeding history, parentage records, and animal performance
  • aggressive culling at signs of defects or lower performance – the starting herd should be as large as possible to accommodate aggressive culling
  • keeping inbreeding levels low

To keep inbreeding levels low, the recommendation is to keep the genetic contribution of the same ancestor to 50% or less (van der Westhuizen, 2016). To illustrate, the progeny of mating a daughter to her sire will have 75% of genetics from the sire. Generally, matings that involve full siblings and parents to offspring are discouraged. Instead, matings of uncle/niece, half siblings, and first cousins are potential strategies.

Outcrossing, or the breeding to non-relatives or distant relatives (i.e., at least 4 generations away) within a breed, is the most widely used mating strategy in purebred herds. Outcrossing can be used to increase performance levels, avoid inbreeding depression, and restore performance lost to inbreeding depression (Evans and McPeake). The more genetically dissimilar the animals, the larger the potential benefit. One drawback of this system is that, if the outcrossed progeny were to be mated, it is more difficult to predict the phenotype of the calves due to the variation in genetic background.

Crossbreeding

With crossbreeding, cattle from different breeds are mated. As the genetics from both parents can be very different, both the positive and negative effects seen in outcrossing are magnified with crossbreeding. Crossbred herds are much more unpredictable in terms of calf weight, maturity time, and nutritional demands. However, there are two key advantages:

  • Heterosis or Hybrid vigor – this is the opposite of the performance reducing effects of inbreeding depression. Heterosis provides improvements, especially in the area of reproduction and growth. The effect of hybrid vigor is dependent on the animal having two different copies of a gene, where the more unrelated the breeds, the larger the potential improvements.
  • Breed complementarity – where the strengths of two different breeds are combined. For example, when mating Charolais bulls to Hereford-Angus crossbred cows, the Charolais bull contributes growth and performance genetics, while the Hereford-Angus cows have desirable maternal and carcass quality attributes. This may not be seen in every individual animal, but is observed in herd averages.

Studies (Gaines et al., 1966; Turner et al., 1968) have found that compared to purebred, crossbred cows have a 10% increase in calf crop and calves weaned, with the calving percentage of the crossbred cows being consistently higher than their parents. Gregory et al. (1978) found crossbred cattle to be 7 kg heavier and 9 days younger at puberty than their purebred counterparts.

Crossbreeding improves reproductive performance, longevity, and maternal ability of the cow. This is manifested through increased calf survival rate, as well as increased weaning weight. Overall, the performance improvements from crossbreeding can have significant impacts on the bottom line of beef producers.

There are many crossbreeding strategies, for example:

  • 2 or 3 breed rotation,
  • terminal cross,
  • bull rotation, or
  • composite breeds.

A terminal cross is where both parents are purebreds of different breeds, and the resulting calves are a 50:50 mix. However, to maintain this specific breed ratio, replacement breeding stock from purebred herds must be used instead of rebreeding the offspring.

Another strategy is mixed breeds, where multiple breeds are used without maintaining specific ratios of each breed in the progeny. While this strategy does not require complex breeding management, there is lower uniformity and a higher level of uncertainty regarding calf performance.

The optimal strategy will depend on the operation itself; for example, if calves are sold at a pre-sort sale or are part of a large group and able to fill an entire feedlot pen, uniformity becomes less important.

For further reading on crossbreeding, NBCEC (2010) introduces an overview of different strategies and Gosey (1991) presents a more in-depth discussion.

There are also challenges and considerations associated with a crossbreeding system (NBCEC, 2010):

  • a small herd (i.e., less than 50 cows) can limit choice in crossbreeding strategies
  • a higher requirement for breeding pastures and bull breeds for the more complex crossbreeding strategies (e.g., rotational systems)
  • more record keeping and cow identification as the current breed composition of cows can affect sire and heifer replacement selection
  • less uniformity in progeny
  • no crossbreeding system can overcome low quality bulls

There is no one-size-fits-all solution or breeding program that is best for all scenarios, as the right genetics depend on the individual operation. Key determining factors include: the management style of the operation, heifer retention (i.e., terminal versus maternal sires), number of breeding fields, and time of marketing. For example, a farm that auctions their calves at weaning may choose a mixed breed program with high calving ease, while a farm that direct markets their beef may prefer the uniformity of a purebred program.

There are many different types of bulls available, and effective sire selection requires an understanding of the characteristics of the available genetics as well as your own operation. Deliberate alignment of the bull’s genetics to your operational goals will contribute to enhanced revenue and reduced costs.

Editor’s note: Stay tuned for part two in this four-part series.

Myths and truths of crossbreeding

Crossbreeding and the resulting heterosis have been utilized for generations. But questions still remain.

Jan 23, 2019

By B. Lynn Gordon

There is always a lot of discussion and debate in the cattle business about crossbreeding. Two Kansas State University researchers have teamed up to answer some of the most common questions beef producers ask about crossbreeding and address whether the questions are myths or truths.

Here are some common questions about crossbreeding.

There are benefits to crossbreeding? Truth.

“The benefits of crossbreeding are heterosis and breed complementarity,” says Bob Weaber, Extension beef cattle specialist. Historically, heterosis or hybrid vigor has been the positive outcome from crossbreeding because of the superiority of a crossbred animal as compared to the average of its straightbred parents. An increase in weaning weight, for example.

Recently, the crossbreeding discussion has included reference to breed complementarity which is the result of taking two different breeds and pairing them to complement the core traits of each breed.

“The focus is to complement each other’s strengths and weaknesses,” says Megan Rolf, K-State assistant professor of genetics. Two animals are crossed to build on the strengths of the individual animals. For example, the muscling featured in one breed to overcome the shortcoming of muscling in the other breed. Basically, it’s building off of a strength of one breed that will complement an area of needed strength in another breed to reach the end goal.

Crossbreeding results in a large increase in calf birth weight? Myth.

A large collection of data from the Meat Animal Research Center (MARC), on a variety of the major U.S. beef breeds and their crosses (over 25,000 breedings/calves in the database), re-estimated the heterosis effects on birth weight, weaning weight and yearling weight including British x British; Continental x British; and Continental x Continental, explains Weaber. “The average increase in birth weight due to heterosis was 1-1.5 pounds,” he says, “not a large increase as often believed.”

The more genetically distant the two parental breeds, the greater the amount of heterosis? Truth.

“The more divergent or different the parental breeds are, the more heterosis a beef producer will see from the mating,” says Rolf. Heterosis is derived from combinations of different alleles (commonly referred to as forms of a gene), from parent breeds, which increases heterozygosity at many places in the genome and helps individuals recover from inbreeding depression.

“For instance, crosses of British breeds like Hereford and Angus creates slightly less heterosis effect than crosses of British and Continental breeds. Crossing Bos taurus breeds with Bos indicus breeds creates substantially more heterosis than just crosses of Bos taurusbreeds,” she notes.

In general, British breeds are more closely related to each other than to Continental European breeds. These breeds are diverged from each other 100-200 years ago. Recent data suggest Bos taurus cattle diverged from Bos indicus 80,000 to 100,000 years ago, making these two groups genetically distant.

Heterosis only exists in the first generation of crossbreeding? Myth.

“The mating of two straightbred animals [of different breeds] in a first cross will result in heterosis. However, the mating of an F1 and two F1 crosses (F1 cattle are the offspring from the initial cross) with the same breed composition will still result in 50% heterosis in the mating,” Rolf says.

“In fact, the mating of two crossbred animals does result in the retention of some heterosis, however, the amount of heterosis retained will be different in different crossbreeding systems depending on the system and number of breeds involved.”

A cross of unrelated lines within a breed, (for example a maternal line with a terminal line) will result in heterosis? Myth.

“Heterosis is not available from within-breed matings, rather only available by mating animals of two or more breeds,” says Weaber. For example, a Hereford x Hereford will not provide heterosis, yet, research indicates the most heterosis will occur from crossing a British animal with a Continental animal or to a Bos indicus animal.

Carcass traits benefit more from crossbreeding than reproduction traits? Myth.

Beef research demonstrates the level of heritability and heterosis are inversely related. As a result, those traits that are highly heritable tend to be the opposite when it comes to heterosis benefits.

“While carcass performance can benefit from crossbreeding, more benefit comes from focusing on breed complementarity than heterosis. Reproductive traits, which are very important to cow-calf producers, are lowly heritable, and thus get a large benefit from heterosis,” says Rolf.

Trait                                         Heritability                    Heterosis

Reproduction (fertility)              Low                              High

Production (growth)                  Moderate                     Moderate

Product (carcass)                       High                             Low

But there is more to crossbreeding than just heterosis, Rolf reminds cattlemen. This is due to the benefits that come from breed complementarity, where the focus is on the core strengths of each breed and allowing these core strengths to compliment each other across the two breeds utilized in crossbreeding. The end goal is to optimize performance levels.

“Producers can enhance the outcome of crossbreeding by taking advantage of the economically important traits like reproduction/fertility that benefit greatly from heterosis but are lowly heritable and then utilize breed complementarity and EPDs to gain a benefit from the more highly heritable traits,” concludes Weaber.

B. Lynn Gordon is a freelance writer from Brookings, S.D.