CATTLE BREEDS AND GENETICS: AN OVERVIEW
Whether you're a non-farming family wanting to raise a steer as a 4-H project, an “old hand” with years of experience raising livestock, or somewhere in between, an overview of beef cattle breeds and genetics will be useful. There are many types and breeds to choose from; you should be aware of them in relation to your goals in raising beef cattle. Also, a practical knowledge of genetics will help you to select and raise good cattle.
Choosing Beef Cattle
When deciding on animals to purchase you may be influenced by earlier experiences, a favorite breed, or the breeds raised in your area. You may like the color of a breed, its unique characteristics or beef production qualities, or its interesting history. Many breeds will thrive in most areas; exceptions include breeds with specific traits that were developed to suit certain conditions (e.g., hot weather and insects of the American South and Southwest). Some breeds will do much better than others in certain regions and climates, and a few are completely unsuitable for some climates. A breed with a long, heavy hair coat and a layer of thick, insulating body fat, for example, won’t do well in a hot, humid climate, and a breed with scanty hair and a body programmed for heat dispersal rather than heat retention will do poorly in a cold climate. Whether there is a market for a certain type of animal in your area should be another primary consideration. Before making a final selection, ask yourself if the breed you are hoping to purchase will work well in your climate and on your place, and whether you’ll be able to sell the calves produced.
If you are raising a few animals for your own use or for sale to friends and family members, it won’t matter if you choose a lesser-known exotic breed, as long as it can thrive in your climate. But if you want to sell the offspring at auction or to local cattle buyers, raise a type of cattle that folks are familiar with; you will have a much easier time selling them.
Be aware that there can be wide variety in quality, body structure, and disposition among animals of any given breed. Select high-quality individuals by figuring the sum of traits that contribute to the animals’ ability to profitably produce beef and that make them desirable to buyers.
Some of the drawbacks of certain breeds can be minimized by crossbreeding (see page 8). You can often combine the desirable traits of two or more breeds in one animal and take advantage of the traits you want, including some that enable the animal to be more adaptable to your particular climate and conditions.
Breeds and Types of Beef Cattle
There were only two kinds of wild cattle in prehistoric times — the Aurochs of Europe (Bos taurus) and the Zebu cattle of Asia, India, and Africa (Bos indicus, the hump-backed, droopy-eared cattle of the tropics). Almost all breeds in America today are Bos taurus. The Brahman is the best-known breed originating from Bos indicus.
Early stockmen learned that they could improve on certain traits if they mated individuals with desired characteristics. If they chose a bull whose mother gave lots of milk and bred him to cows that gave lots of milk, the daughters might be even better milk producers. Other cattle lines were selectively bred to produce bigger, stronger animals for pulling carts. These “draft” breeds had lots of muscle and large carcasses. When cattle were no longer needed for draft, stockmen chose these heavy-muscled cattle and modified them futher to create beef animals. These were the ancestors of modern beef breeds.
Soon stockmen raising certain types of cattle created registries and formed organizations to develop standards and rules that breeders must follow when selecting their animals. Thus the characteristics of each breed were established and standardized, so that all cattle in that breed would be somewhat uniform and would embody the desired traits.
Many new breeds have been created in the past 50 years by selectively breeding and combining older breeds. Today there are many beef breeds with different characteristics in size, muscling, milking ability, calf size, carcass traits (lean or fat), weather tolerance, hair color, markings, and more. Some have horns; some are polled (hornless). Some are descendants of cattle from the British Isles, Europe, or India. Many modern American breeds are mixes of early imported breeds.
HORNED AND RED BREEDS WITH BLACK AND POLLED TRAITS
Some of the traditionally red and horned breeds, including Simmental, Limousin, Gelbvieh, and Salers, now have some family lines that are black and polled. Due to the exceptional popularity of black, polled cattle, some breeders have added black, polled genetics to the red, horned breed. By utilizing selective breeding and taking advantage of the fact that black and polled are dominant traits, some black and polled lines have been created within almost all of the red, horned breeds.
Crossbreds
Crossbreeding is used to combine the traits of two or more breeds. A crossbred animal has parents of different breeds. In fact, most breeds in existence today originated through crossbreeding — followed up by selective breeding to “fix,” or standardize, certain traits.
Crossbreeding can often produce in just one or two generations what it would take many generations to achieve in purebred animals (and may perhaps never be possible, depending on what breed you started with). Indeed, crossbreeding is the most useful tool available to the beef producer because no single breed is best in all traits important to beef production.
Heterosis (or hybrid vigor) results when you mate two animals that are very different genetically. The offspring is superior to either parent. If your goal is to raise larger calves or more fertile cows that live longer, milk better, and are more feed-efficient, you can achieve this goal more quickly by careful crossbreeding.
Which Type Is Best?
Unless you have a preference, it doesn’t matter what breed or crosses you start with as long as they are good-quality individuals with traits you want. All breeds have strong points and faults. Even if an animal is of a certain breed or type you think highly of, judge it carefully as an individual to make sure that it is what you want.
When selecting cows or heifers to start a herd, decide whether you want to raise registered purebreds, straightbreds (cattle of one breed but not necessarily purebred or registered), crossbreds, or composites (blends of traditional breeds into a uniform type of crossbred with fixed, valued characteristics). A registered heifer may cost more than a commercial (unregistered) heifer, but she may not be better; she just has registration papers (which should be transferred to you at purchase) and you could sell her calves as purebreds if you breed her to a registered bull of the same breed. To sell the calves as purebreds, you must register them after they are born. You must also join the breed association and pay a fee, as well as a registration fee for every calf you register.
Only the best heifers should be kept as cows, whether purebred or commercial cattle, and only the very best bull calves should be kept or sold for breeding purposes. Most bull calves should become steers. The only way to maintain or improve quality of beef herds is to use superior breeding stock.
If you plan to raise purebreds, shop around when selecting your first animals and evaluate them as individuals. If you are not experienced in judging cattle, have a knowledgeable person help you make your selections.
If you want to raise good-quality calves that will make good beef animals or calves that will be in strong demand for sale to cattle feeders, you should raise commercial cattle rather than purebreds. Then you can take advantage of benefits gained from crossbreeding.
Inheritance of Traits
Genes and chromosomes determine inherited traits. Genes (the chemical codes that transmit traits) are located on the chromosomes (long strands of genetic material carried in each cell of the body). Chromosomes occur in pairs. As cells divide, half the genetic material goes with the new cell; it is a perfect replica of the old one (except when chromosomes become twisted or misplaced, resulting in mutations).
Each cell contains several different chromosome pairs that carry the code of inheritance. Egg and sperm cells have only one chromosome from each pair, however, so that when egg and sperm unite, the newly formed pairs are a joining of one from the male and one from the female; the offspring inherits half its genetic material from each parent. Because there’s such a large variety of genetic material in genes and chromosomes, possibilities for different match-ups are great. No two calves (even full brothers or sisters) are ever exactly alike, except identical twins, which are produced by the splitting of the fertilized egg.
Dominant and Recessive Traits
Most characteristics are determined by several sets of genes. Some genes are dominant and some are recessive. When chromosomes come together to form a new individual, two genes (one from each chromosome — one from each parent) control the trait. If one is dominant, the trait it represents will show up in the offspring. The trait represented by the recessive gene won’t be expressed with the dominant gene present but might be passed to future offspring if not masked by a dominant gene in that next union.
Traits controlled by dominant and recessive genes are readily seen, such as color or horns. For instance, the Hereford’s white face is due to a dominant gene. When a Hereford is bred to another breed, offspring have a white face.
Not only is white dominant, but the Hereford also carries no other gene for face color, so all offspring from that first cross inherit the white face.
Red and black are controlled by dominant or recessive genes; red is recessive and black is dominant. If a red animal mates with a black one, all offspring are black unless the black parent carries a recessive red gene. The offspring can be red if it inherits a recessive red gene from each parent. Two reds mated can produce only red offspring. Two black parents can produce a red calf if both carry a red gene and the calf inherits the red gene from each.
Color is more complicated with roans, grays, and shades of brown and tan because of factors other than simple dominant or recessive genes; some are influenced by more than one pair of genes. In some breeds, colors are not clearly dominant or recessive.
Horns are determined by one pair of genes in a simple dominant-recessive relationship. Polled is dominant. If a homozygous (only polled genes) polled animal is bred to one with horns, the calf will be polled. But if a heterozygous (polled, carrying recessive horned gene) animal is bred to a horned one, the calf has a 50 percent chance of being polled (but carrying recessive horned gene) and a 50 percent chance of being horned (carrying a recessive horned gene from each parent). If two heterozygous polled animals are mated, offspring have a 50 percent chance of being polled and carrying a recessive horned gene, a 25 percent chance of being homozygous polled, and a 25 percent chance of being horned.
Horn scurs occur with mixed genetics. Scurs are incompletely developed horns, often loosely attached, ranging from tiny hard scabs to large protrusions that resemble horns. Additional genes or more than one pair of genes may be responsible for their development, since this is a sex-linked trait. Because scurs are genetically dominant in males and recessive in females, a greater number of males end up with scurs than do females.
Black heterozygous bull (Br) bred to a black heterozygous cow (Br): Offspring have a 25 percent chance of being homozygous black, a 50 percent chance of being heterozygous black (carrying a recessive red gene), and a 25 percent chance of being red.
GENETIC DEFECTS
Some undesirable traits or genetic defects are inherited. Most commonly the defective calf inherits a recessive gene from both sire and dam (as in dwarfism — parents are normal but both have defective recessive genes). A few defects are caused by genes with incomplete dominance,
and some are caused by two or more sets of genes. Genetic defects often run in families, making inbreeding (mating closely related animals) risky. Parents of a genetically defective calf often have at least one ancestor in common.
Examples of genetic defects:
1. dwarfism
2. water on the brain (hydrocephalus)
3. marble bone (ostepetrosis — marrowless, brittle bones)
4. hairlessness (hypotrichosis)
5. curly calf (stillborn with curved spine and extended leg bones)
6. mulefoot (two toes fused together)
7. parrot mouth (short lower jaw)
8. extra toes (polydactyly)
9. double muscling
To avoid genetic problems, buy bulls or semen from reputable breeders and avoid inbreeding. Crossbreeding rarely produces genetic problems.
Crossbreeding and Hybrid Vigor
Hybrid vigor (heterosis) is a phenomenon associated with crossing two breeds or species, creating traits in the offspring that are superior to those of the parents. Crossbred cows are more fertile than either parent breed. Crossbred calves are hardier and have a higher survival rate due to their stronger immune systems. They also gain faster, grow bigger, and adapt more easily to harsher environments. Heterosis beneficially influences traits such as feed efficiency and longevity, vital to beef production. Generally, the more diverse the breeds, the greater the heterosis in the calves — as when crossing Brahman with British breeds. Greater response of heterosis is also gained by crossing British breeds with Continental breeds than by crossing them among themselves.
Advantages of Crossbreeding
Many beef breeds and even a few dairy breeds can aid a beef crossbreeding program. Crossbreeding isn’t used much by dairies (80 percent of U.S. milk is produced by Holstein cows, and the rest by five other breeds that are rarely crossed). Dairy cows are bred for the maximum expression of a single trait: milk production.
By contrast, beef producers raise cattle in a wide variety of environments and conditions, and each stockman must create a herd that will perform efficiently and produce good calves in his unique situation. Thus many stockmen crossbreed, since no one breed has all the traits that might be needed in creating the most efficient cow or producing the most pounds of beef at least cost.
With careful crossbreeding — combining traits from two or more breeds and taking advantage of the added hybrid vigor — it’s possible to develop a herd of crossbred cows that perform exceptionally well. The practice of cross breeding is most beneficial to beef production when a stockman uses crossbred cows. They are the key to profitability in a cow-calf operation because hybrid vigor in the cow produces phenomenal maternal advantages. Research has shown that a crossbred cow is 8 percent more efficient (more performance on less feed) than a purebred cow, lives 38 percent longer, and has 25 percent more lifetime production in total pounds of calves weaned. This performance is partly due to the fact that crossbreeding beneficially affects traits such as fertility, age at puberty, and longevity — traits that are not easily improved by selective breeding within a breed. Because crossbred cows have increased fertility, they are less apt to be culled for being open after breeding or for calving late in the season. Any cow that can calve at 2 years of age, never miss a year of calving, and stay in your herd a year or more longer than average culling age makes you money.
Research has also shown that part of the reason crossbred animals are hardier than purebreds is due to a stronger immune system. They develop better immunity when vaccinated, and the crossbred cows supply their calves with colostrum that contains more antibodies, which in turn keeps them healthier through the risky days of early calfhood.
Weaning weights for crossbred calves produced from parents of two different breeds are generally about 5 percent higher than those of straightbred calves. A study in the 1990s found that a crossbred calf netted a producer an average of $23.37 more than a straightbred calf. But a crossbred cow with a crossbred calf netted an average of $116.88 more than a straightbred cow with a straightbred calf.
Even though one benefit of crossing two breeds is increased growth in the offspring, the benefits of most value to the stockman, over time, are increased production of the crossbred female, greater fertility (even under adverse conditions), better maternal traits such as milking ability, and increased survival rate of the calves. Crossbred females are a herd’s best producers.
CROSSBREEDING MAXIMIZES GENETIC POTENTIAL
Because all breeds were created by some degree of inbreeding to “fix” desired traits for uniformity in the offspring, breeding animals within the same breed always limits genetic potential. A breed is essentially a closed group of cattle that excludes infusion of any other genetics and therefore accumulates inbred traits over time. Inbreeding doubles up recessive genes in the limited gene pool, limits variety, and increases the probability that inherited defects will crop up. By inbreeding during the early history of the breed to gain uniformity, some degree of beef production potential — the opportunity for maximum growth and vigor — was sacrificed.
Crossbreeding is the opposite of inbreeding; it opens the door for wider genetic variation and results in heterosis, which is essentially the recovery (or reversal) of accumulated inbreeding depression. In just one generation, the crossbred offspring exhibit the greatest degree of what was lost in growth and vigor through many generations of pure breeding within a closed gene pool.
Crossbreeding Techniques
There are many types of crossbreeding programs. The traditional program involves breeding cows of one breed to a bull of another to produce a 2-breed cross. This program requires the stockman to buy all replacement heifers to keep them of one breed, and it makes the least use of hybrid vigor in the cows.
Another program that more optimally maximizes heterosis calls for pairing crossbred cows with a bull of a third breed. This technique is often done by stockmen who want to produce maximum growth in beef calves by using very maternal breeds in the crossbred cows and mating them with a bull of a “carcass” breed that is heavy muscled (see below).
Other stockmen use a 2- or 3-breed rotational cross, keeping the crossbred heifers in their herd. For instance, if they breed Angus cows to a Hereford bull, the Angus-Hereford heifers would be bred to a Hereford or Angus bull. Resulting calves would be ¼ one breed and ¾ the other. Then they breed those heifers back to the other breed, alternating Hereford and Angus bulls on the crossbred cows. Cows must be identified by breed of sire so they can be bred to a bull of the other breed. This program generates its own replacement heifers but requires two breeding pastures.
The same can be done for a 3-breed rotational cross, using bulls of the three breeds alternately. For example, if the third breed is Limousin, Hereford-sired females would be bred to an Angus, Angus-sired females to a Limousin, and Limousin-sired females to a Hereford. A 3-way cross increases heterosis in calves and maternal heterosis in cows. All cows are a mix of the three breeds.
Some stockmen feel this is too complicated and requires too many breeding pastures. An easy way to use three or more breeds is to use crossbred bulls as well as crossbred cows. If they like the results from a certain 3-way or 4-way cross, they keep the herd that way by using crossbred bulls — instead of alternating between various breeds of bulls.
For instance, if they like the Angus-Hereford cross, they use Angus-Hereford bulls with Angus-Hereford cows. Then they don’t have calves that are ¾ one breed and only ¼ the other. Or they use Hereford-Angus bulls with Hereford-Angus-Simmental cows (or any other mix), or Simmental-Hereford bulls with Limousin-Angus cows (or any other preferred cross), to create a 4-way cross in just one generation. By continuing to use crossbred bulls on crossbred cows, they keep the mix about the same and also keep most of the hybrid vigor.
Some stockmen use a terminal cross, breeding crossbred cows to a third breed (such as Charolais, Simmental, Chianina, or any breed that produces large, fast-growing calves) and selling all offspring. This creates maximum pounds of calf, especially if the crossbred cows are a mix of breeds that give superior maternal qualities. The disadvantage is in having to buy the replacement heifers or breed some of the cows to a different bull for producing heifers to go back into the herd. A combination of rotational and terminal crosses works with a 2-breed rotation on young cows and a terminal sire on older cows for large calves to sell. Replacement heifers can be kept from offspring of the young cows.
Other systems can be used, such as simply changing the breed of sire after 3 years. If you plan to keep replacement heifers, use a blend of breeds noted for good maternal qualities. With so many genetics to choose from, you can develop the type of cow you want.
Composite Cattle
A composite animal is created by mating crossbred animals of similar breeding; the breed mix is the same in both sire and dam and has been standardized into a predictable blend over several generations of breeding crossbreds to crossbreds. The animals are all the same percentage of specific breeds, such as half and half of two breeds or ⅜ one breed and ⅝ another or a certain blend of three or more breeds. Some “breeds” in use today like Brangus (Angus/Brahman), Santa Gertrudis (Shorthorn/Brahman), and Beefmaster (Shorthorn, Hereford, and Brahman) were begun as composites. Many popular composites exist today, such as Angus/Gelbvieh, Angus/Salers, Chiangus (Angus/Chianina), and numerous other combinations of British and continental breeds.
Some of the most productive composites mix beef breeds with a dairy breed such as Holstein, Brown Swiss, or a European breed known for milking ability. A little dairy blood adds maternal qualities and enhances femininity and fertility, producing a superior beef cow that is hardier, more efficient, and more versatile than any dairy cow.
Use of composites simplifies crossbreeding for the small operator because it involves breeding composite cows to composite bulls, which is like breeding crossbred cows to crossbred bulls. The rancher who uses composites need not worry about various mixes and different breeding pastures, and the animals produced retain the desired genetic blend and a high percent of the hybrid vigor.
When you use composites for crossbreeding, you can take advantage of genetic differences between breeds to select, achieve, and maintain a high performance level for many economically important traits. Therefore, you can produce cows that excel in your environment and whose calves meet your targeted market (grass finished or grain finished, for instance). Composites (home grown or commercially available) enable a stockman with any size herd to tailor the cattle to meet goals for optimum body size, fertility, milking ability, calves with exceptional growth rate, and carcass traits.
Crossbreeding, or use of a desirable composite that you’ve either created yourself or purchased, can help your herd to avoid certain reproductive and health challenges (such as calving difficulty, or cancer eye in white-faced cattle, among others) and can add traits that improve on hoof health, milk production, udder and teat conformation, and disposition, for example — qualities that may be in short supply in your present herd.
The easiest way to use the advantages of crossbreeding is to have composite cattle or to work into a mix of your own by starting with whatever cows you have and then selecting a bull of a different breed (or a crossbred bull) that will complement or enhance the cows’ qualities or add desired traits.
Maintaining the Positive Effects of Heterosis
The maximum benefit from heterosis is in the first generation (F1), in which a crossbred animal is produced from different parent breeds. The next generation (F2) loses some of that vigor if the F1 animal is bred back to one of the parent breeds. Breeding the F1 to a third breed resolves that problem and again creates maximum heterosis.
There are various degrees of hybrid vigor in calves produced from different crossbreeding systems, such as a 2- or 3-breed rotational cross. To get an idea of the range of differences, breeding a purebred to a purebred of the same breed produces 0 percent heterosis, and breeding individuals from two different breeds (especially if the breeds are very genetically different) results in 100 percent heterosis. Breeding a crossbred to another crossbred (same two breeds) results in 50 percent heterosis. In a traditional 2-breed rotational cross in which the crossbred cow is mated to a bull of one of the parent breeds, the calves are ¾ one breed and ¼ the other. If those daughters are bred back to bulls of the other breed, and the bull breed is continually switched back and forth with each new generation, the heterosis obtained stabilizes at about 67 percent. Adding a third breed to the rotation (switching sires for each generation between the three breeds) extends the effects, resulting in 86 percent heterosis in each generation. Adding a fourth breed to the rotation results in an increase to 93 percent heterosis, which continues indefinitely in each crop of calves from the mix.
One disadvantage to any kind of rotational system that utilizes purebred bulls is that you need several different breeding pastures and must sort the crossbred cows into groups, based on the bull that should breed them, in order to produce the desired percentage in the calves. Also, the breed makeup of the calves swings heavily (more than half) toward the breed of sire in each generation. These drawbacks can be resolved by using crossbred bulls or composites. Then the breed mix in the calves can stay the same or remain very similar, and heterosis still plays a significant role in the traits of the calves. A composite utilizing two breeds that contribute equally to the mix will consistently deliver 50 percent heterosis, while a 4-breed composite in which all four breeds are used equally will contribute 75 percent heterosis, in each generation, continuing over time, unless the composite animals within the herd are inbred once again.
Selecting for Certain Characteristics
When breeding beef cattle, one goal is to produce fast-growing calves with high weaning and yearling weights, to bring more money at market with less time and feed expense. Another important goal is to keep improving the quality of heifers kept for the herd, creating cows that are highly productive yet economical to feed. Keep in mind that the bigger the cow, the more feed she will eat. Very large cattle generally do not produce enough extra pounds of beef (calf size at weaning) to justify their extra feed requirements. Genetic selection can shape your herd by creating individuals with improved milking ability, udder shape, disposition, fertility, optimum size for your farm’s forage production — or whichever traits you prioritize for your business.
Some traits are passed from father to daughter or from mother to son. For instance, many important maternal traits (e.g., udder shape, teat size, milking ability) come more from the sire than the dam. The daughters of a bull may inherit many characteristics from his mother. If you want to raise heifers with good milking ability and nicely shaped udders (small teats instead of long or fat ones), select bulls carefully; their mothers should have the traits you want in your cows. A small, efficient udder is best, since it is more likely to hold up over the years without breakdown and is less likely to give problems at calving time, such as teats too large or too long for the calf to get into his mouth. The growth rate and size of a cow’s calf at weaning is a much better indication of her milking ability than is the size of her udder.
For fertile, high-producing cows that wean big calves, select for milking ability and maternal qualities — long feminine head and neck, graceful angles, and well-shaped udder with thin skin and small teats. A heifer that looks like a steer (too masculine) may be big and beefy but is genetically less likely to be a good cow.
The study of genetics, especially as it applies to your own herd, is not only fascinating but also helpful to herd management. It can help you to more wisely select breeding stock and develop a herd that will perform well and best suit your purposes. You will be able to raise better calves, not just in terms of increasing the weaning weights of those you sell, but also in terms of increasing the productivity and longevity of the females you keep.
SOME GENETICALLY LINKED TRAITS
1. disposition
2. conformation (body structure) and size
3. birth weight
4. early puberty (thus, fertility)
5. scrotal size in bulls
6. longevity
7. gestation length
8. udder characteristics
9. vulnerability to certain diseases (e.g., cancer eye)
By Heather Smith Thomas in "Storey's Guide to Raising Beef Cattle", Storey Publishing, USA, 2009, chapter 1. Adapted and illustrated to be posted by Leopoldo Costa.
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