Developing a Breeding Program to Produce the Optimum Carcass
by Don Kress, Professor of Animal Science
MSU Department of Animal and Range Sciences
The potential value of genetic improvement in carcass characteristics is large. Optimum targets for carcass traits are fairly clear, even though they may vary according to marketing strategy, and give beef cattle breeders clear targets for aiming their breeding programs. Within breed, genetic improvement requires that we identify sires which produce progeny that match the targets — and this means that we must make EPDs for carcass traits a high priority. Choice of breeds is the key issue for breeding programs that utilize multiple breeds. The breed combination target of 50% British — 50% Continental is often a good way to optimize trade–offs. In situations where the same breed combinations optimize cow maternal performance and meet the optimum targets for carcass traits, composites or rotational crossbreeding systems will work very well. Use of F1 or composite sires in rotational systems will improve uniformity and consistency of the end product. In situations where the same breed combinations do not optimize both cow maternal performance and targets for carcass traits, terminal sire systems should be considered because they allow the genetics of the end product to be different from the genetics of the cow herd. Use of AI and sexed semen will make terminal sire systems even more efficient and practical to use.
Figure 1. Average level of production per beef cow (Cattle-Fax, 1995)
Introduction
This is a very logical point in time for the beef industry to be emphasizing carcass traits. Firstly, our industry has made tremendous gains in the productivity per cow in the last 30 years (see Figure 1.Thus, it is likely that we are nearing optimal values for cow productivity in many of our environments and that emphasis of selection programs can be moved to other traits. Secondly, many producers have their cow herds at or near optimal levels for cow size and milk production. This, combined with the demonstrated need for improvement of our end product, means that considerable genetic emphasis can be placed on selecting for carcass characteristics in the near future in many of our beef herds. Seedstock breeders need to take the lead in this endeavor, but commercial producers need to play an important role as well.
What is the Reward?
It is clear that there has been an increase in the relative importance of carcass traits over the last few years. Table 1 (below) shows one example. Almost 20 years ago in 1979 reproductive traits were 10 times more important than carcass traits, and growth traits were 5 times more important. This resulted in little motivation for beef cattle breeders to emphasize selection for carcass characteristics. However, by 1995 a large shift had occurred and carcass traits were of equal importance with growth and half as important as reproduction. Some would argue that carcass traits are even more important than growth.
Table 1. Change in Relative Importance of Beef Cattle Traits
| Trait | 1979 | 1995 |
|---|---|---|
| Reproduction | 10 | 10 |
| Growth | 5 | 5 |
| Carcass | 1 | 5 |
| Melton (1979, 1995) | ||
In actual dollar values, the 1995 National Beef Quality Audit estimated a potential loss in value of $138 due to quality of end product for every fed beef steer or heifer marketed. The 1995 Texas Ranch to Rail Program found a $376 per head difference in net return between the top 10% and the bottom 10% of steers — meaning that if your herd is average you have a potential gain of one half of $376 or $188.
Not all of the $138 to $188 difference in value is genetic, so let’s be conservative and say that 30 to 40% (approximate heritability values for carcass traits) of the differences are genetic. This suggests that the potential value of genetic improvement of carcass traits is $40 to $75 per head — which makes it very worthwhile for most any breeding program to emphasize selection for carcass traits!
What is the Target?
Table 2 shows a set of targets for carcass traits that a breeder could use for guiding a breeding program. These are the target values for the progeny produced in the breeding program. In other words, if the cows in the herd are widely different than these target values, then the sires should be selected so that the resulting progeny would match up with these values. For example, if the genetic potential of the cow herd is to produce too much fat, then sires would be selected to correct for too much fat. Depending upon your market, these targets might change somewhat from one herd to another.
Table 2. Select Sires (Breeds) for Optimum Performance
| Progeny Carcass Trait Targets | ||
|---|---|---|
| Fat | Fat Thickness, in. | 0.35 |
| Muscle | Ribeye Area, sq. in. | 13.2 |
| Weight Carcass | Weight, lbs. | 750 |
| Cutability | USDA Yield Grade | 2.5 |
| Quality | USDA Quality Grade | Choice |
| Tenderness | Shear Force Test, lbs. on middle meats | <8 |
Another good way to evaluate proper targets is to examine an example pricing grid (Figure 2 at end of article) group of 70% Choice cattle. Premiums are paid for yield grade 1 and 2 carcasses, and yield grade 4 and , assuming a5 carcasses are discounted heavily. Premiums are paid for greater quality grade (marbling), but standard carcasses are heavily discounted. The answer is clear, the target carcass has a high quality grade (marbling) and is yield grade 1 or 2. However, the problem is that there is a genetic antagonism (trade–off) between quality and yield. Generally, we have to sacrifice quality to get high yield, or we sacrifice yield to get high quality. We will follow up with some answers to this dilemma in the section below titled "What is the Effect of Trade–offs?," but the answer is usually an optimum carcass that is not extreme in either characteristic.
Breeders, especially seedstock breeders, need to know how their cattle fit the grid. Two examples are illustrated in Figure 3 for two groups of 100 carcasses. Part (a) shows a group of cattle that had a high percentage of yield grade 1 and 2 carcasses, but only 60% graded Choice. These carcasses are quite tightly grouped (consistent), and represents a very desirable group of cattle for a market that emphasizes high yield. Part (b) shows another group of that cattle that is quite different, with 90% Choice, but only 50% yield grade 1 and 2. These cattle might well fit another marketing scenario, but note that they are more spread out and are less consistent. Breeders need to know how their cattle fit the grid. You need to have that information to know what needs fixing. In a 1995 NCA survey, only 40% of feedlot and stocker operators said they would price calves differently based on past carcass data and a recent Montana survey indicated that less than 15% of the breeders collected data on carcass weight, yield grade, or quality grade. More breeders need to be collecting carcass data so that we know what traits need to be improved in our Montana herds. When we have collected carcass data (through an alliance, branded beef program, USDA tags, etc.), Montana cattle have stacked up pretty well against other cattle.
Figure 3. Distribution of 100 carasses on the grid.
| (a) Yield: 96% 1’s & 2’s | |||||
| Grade: 60% Choice | |||||
|---|---|---|---|---|---|
| Lean 1 | 2 | 3 | 4 | 5 Fat | |
| Prime | |||||
| Upper 2/3 Choice | 1 | 3 | 1 | ||
| Low Choice | 15 | 38 | 2 | ||
| Select | 15 | 23 | 1 | ||
| Standard | 1 | ||||
| (b) Yield: 50% 1’s & 2’s | |||||
| Grade: 60% Choice | |||||
| Lean 1 | 2 | 3 | 4 | 5 Fat | |
| Prime | 4 | 6 | 2 | ||
| Upper 2/3 Choice | 5 | 9 | 1 | ||
| Low Choice | 2 | 32 | 28 | 1 | |
| Select | 1 | 6 | 3 | ||
| Standard | |||||
The sleeper here, in my opinion, is that the Figure 3 grid does not consider the value of increased and consistent tenderness. I believe beef cattle breeders need to also collect data on tenderness so that we can identify sires that produce progeny with tender steaks. The breeders that get a jump–start on selecting for tenderness are likely to be well–paid for their efforts.
The last point relative to targets for optimum carcass traits, is that some times the genetic potential of cows that match well with our range and resources is different from the genetic potential of progeny that produce the optimal end product. When this happens, it is more difficult to deal with when you have a single breed or single composite, but can be effectively dealt with by using a terminal sire crossbreeding system.
Do Branded Beef Programs Influence Breeding Programs?
They sure do! I believe that branded beef programs have been good for our industry and are here to stay. If you market through the Certified X Program, most times you will need to produce market progeny that are 2 breed X. This can be effectively done in several ways that many times also improves consistency: 1) Use breed X bulls on your cows — or vice versa. 2) Use a composite that is 2 breed X. 3) Use F1 bulls that are 2 breed X (cows must be at least 2 breed X also). 4) Use a terminal sire crossbreeding system where the terminal sire is breed X.
What is the Effect of Trade–offs?
Trade–offs, or genetic antagonisms, influence several important traits of beef cattle. A genetic antagonism between traits X and Y means that as we improve the genetic potential for trait X, the genetic potential for trait Y decreases — the amount of the decrease depending on the degree of the antagonism.
The primary trade–off among carcass traits is between yield and quality. For example, high yield breeds tend to have a lower quality grade. Other important trade–offs in beef cattle are between rapid growth and calving ease, between fertility/reproduction and low fat/high yield, and between cow mature size and rapid growth. Maybe these trade–offs are nature’s way of keeping traits in balance?
Research and experience have shown us that one effective way of dealing with these trade–offs is to have a target in our end product of 50% British — 50% Continental (50B-50C). In other words, a 50B–50C carcass is one way to optimize the balance between marbling and yield. The other way to deal with trade–offs is within breed selection for unique individuals (usually sires) that are superior for both traits. The best way to do this is to use a selection index, but it can also be accomplished through use of independent culling levels (minimums or maximums for each trait under consideration). This type of selection has been shown to be effective for low birth weight and greater growth rate in beef cattle and should be effective for other genetic antagonisms as well.
Is Ultrasound the Answer?
A quick summary of the research results is that real–time ultrasound is quite accurate at predicting fat thickness and longissimus muscle area, but that accuracy is still questionable for predicting intramuscular fatness and palatibility traits. The key issue relative to genetic improvement programs is the accuracy of genetic prediction. In other words, does the measurement on yearling bulls accurately predict the desired carcass trait in steer or heifer progeny? There is very little research to date that says the accuracy is high for marbling and palatibility traits.
What about Genetic Markers?
The easiest genetic answer would be to identify a genetic marker that guarantees a certain level of marbling or tenderness. But, to date it has not been that easy, probably because these traits are caused by many genes. No doubt genetic marker information will be used as a tool to increase the accuracy of EPDs for carcass traits, but I do not think we can afford to sit and wait for a possible genetic marker to save the industry.
How do I Genetically Improve Carcass Traits?
The key point to remember is that carcass traits generally have high heritability and low heterosis (Table 3). This means that genetic improvement will primarily be achieved through selection — either within breed or among breeds.
Table 3. Heritability and Heterosis of Beef Cattle Traits
| Trait | Heterosis | Heritability |
|---|---|---|
| Reproduction | High | Low |
| Growth | Mod | Mod |
| Carcass | Low | High |
Within breeds or within composites, we need to shift more selection pressure to carcass traits. As with most within breed selection programs, most of this genetic change will result from sire selection. This means that we need to identify sires that produce progeny superior for carcass traits of importance. Individual seedstock breeders need to do this, but the most critical need is that we must make EPDs for carcass traits a high priority. Breed associations are working on carcass EPDs, and various associations are at different points in development of carcass EPDs, but we all must work together to make this happen as soon as possible.
Since heterosis for carcass traits is low, we don’t utilize crossbreeding systems to produce heterosis for the purpose of genetically improving carcass traits. But, crossbreeding systems can be effectively used to combine different breeds in proper combinations to produce optimum carcasses. So, the intent is to use crossbreeding to produce a product that meets our target — such as the 50B–50C target — and at the same time produces a consistent product.
There are three primary ways to do this:
- Composites
- Rotational systems with F1 sires or composite sires, and
- Terminal sire systems. The first two will work well when the required genetic potential of the cow herd (to match cows with range and resources) also matches well with the desired genetic potential of the marketed progeny. If the two are widely different, such as a situation where 100% British breeding is required in the cows and the end product needs to be 50B–50C, then a terminal sire system is ideal. It looks like sexed semen is now a reality, and sexed semen combined with a good AI program would make terminal sire systems difficult to beat. All of these systems produce a consistent product. They all can produce market progeny that are 2 breed X. They all can produce carcasses that are 50B–50C. And, they all can maintain a crossbred cow herd.
Composites are available from many seedstock producers and many of the composites hit the 50B–50C target. If your range environment is quite extensive and you don’t believe it can support a 50C cow, then there are 75B–25C composites available that may be optimum for you. Or, make sure the 50C component is made up of smaller continental breeds.
Rotational crossbreeding systems are used by many breeders, but their consistency and uniformity of both cow herd and end product can be improved by using F1 or composite sires in the rotation. One of my favorites is the rotate F1 sire system, where each F1 sire is 50B–50C. Or, it can be modified (as in Figure 4) so that each of the F1 sires (or composite sires) has a breed in common — this gives a very consistent product, can produce a 50B–50C product, and can match up very well with a Certified X Program of branded beef.
Figure 4. Illustration of a two — pasture rotation that uses F1 sires that have a breed in common.
Two-pasture rotation using F1 sires that have a breed in common require:
- two breeding pastures or AI
- same attributes as two–breed rotation except it increases uniformity, allows consistent 50% British – 50% Continental composition of herd and decreases heterosis somewhat.
- excellent system to maintain 50% of one breed.
- genetic improvement determined primarily by genetic potential of SdRa and SaRa sires.
- expected to increase calf production per cow exposed by 18%.
Terminal crossbreeding systems are used less frequently, but offer a lot of potential for the situation where the market progeny need to be quite different from the cow herd.
Rotational–terminal (Roto-term) systems (Figure 5) offer significant advantages for producing replacement females. Sexed semen and AI make these systems even more efficient because all female calves can be produced from the rotation for replacements (making the proportion of the herd in the rotation much smaller) and all male calves can be produced from the terminal part of the system and marketed. These steer calves could be all from progeny–tested sires for carcass traits (or all sires with EPDs for carcass traits), all 50B–50C, all 2 breed X for branded beef programs, and very consistent and uniform. This, of course, is where double–muscled breeds could be used as terminal–sire breeds.
Figure 5. Illustration of a rotational — terminal sire crossbreeding system where the rotational part of the system uses two pastures and F1 sires.
Figure 5 rotational/terminal sire system using two pastures and F1 sires requires:
- three breeding pastures or AI.
- Same attributes as traditional rotational–terminal system except F1 sires increase heterosis, increase uniformity and allow consistent 50% British/50% Continental composition of herd.
- Genetic Improvement determined primarily by genetic potential of TA, SiH, and C sires.
- Expected to increase calf production per cow exposed by 23%.
Details on the crossbreeding systems named above and about two dozen other crossbreeding systems are in the recently revised A Crossbreeding Beef Cattle for Western Range Environments. This bulletin may be obtained by sending $5 (payable to MSU — Animal and Range Sciences) to Dr. Don Kress, Animal and Range Sciences Department, Montana State University, P.O. Box 172900, Bozeman, MT 59717–2900.