University of FloridaSolutions for Your Life

Download PDF
Publication #AN116

Florida Cow-Calf Management, 2nd Edition - Planning the Breeding Program1

Bob Sand, Mark Shuffitt, Pat Hogue, and Tim Olson2

Quality of the cattle produced by the beef industry is determined primarily by genetic makeup. The genetic makeup of cattle is controlled by breeders, both purebred and commercial. According to a report from the National Cattlemen's Association (Beef Business Bulletin, June 1983), about one-fourth of the calves born in the United States each year are of such poor genetic quality that they will not produce profits for any of their owners— producer, feeder, nor packer.

Genetic improvement can be accomplished by using two basic methods: selection and mating systems. Purebred producers generate genetic improvement almost exclusively through selection. Commercial producers also generate improvement through selection, but they use mating systems as well, especially crossbreeding.

“Selection” refers to the breeder's decision to use some animals as parents and to cull others. For selection to be most effective, breeders must be able to identify superior animals. This is done by placing emphasis on economically important traits that are heritable (meaning they can be inherited). National sire summaries, which furnish information on the traits of various bulls, are available from most breed associations. By using artificial insemination (AI), the average producer can select a bull of proven breeding value from the national herd rather than using a bull of lesser quality.

Since most sires are purchased from purebred breeders, these breeders exert great influence on the direction of the beef industry. Commercial producers are now insisting that purebred seedstock producers keep records and make these records available. It is important that both purebred and commercial producers understand and employ the principles and tools of genetic improvement.

Basis for Genetic Improvement

Some differences among animals result from external factors due to their differing environments; the rest are hereditary differences, transmitted to offspring by their parents. With minor exceptions, each animal receives half its inheritance from its sire and half from its dam. Inheritance units are known as genes and are carried on pieces of threadlike material (present in all cells of the body) called chromosomes. Cattle have 30 pairs of chromosomes. Chromosomes and genes both exist in pairs: one gene from each pair is located at its own specific position on a particular chromosome; the second gene is located at an identical position on the corresponding paired chromosome. Thousands of pairs of genes exist in each animal, and one member of each gene pair comes from each parent.

Tissues in the ovaries and testicles produce the reproductive cells. Each cell contains one member of every chromosome pair. The particular gene from each gene pair that goes to the unpaired chromosome in a given reproductive cell is determined purely by chance. When a male's reproductive cell fertilizes a female's reproductive cell, the full complement of genes is restored. Some reproductive cells will contain more desirable genes for economically important traits than others. The union of reproductive cells containing high proportions of desirable genes for economically important traits results in a superior individual and offers the opportunity for selection. The random segregation of genes in the production of reproductive cells and the recombination of genes upon fertilization create the possibility of genetic differences between offspring of the same parents.

Genetic merit within a large group of the same parents' offspring will average that of the parents. By definition, some individuals will be genetically superior to that average, and others inferior. Those superior animals provide the opportunity for selection and genetic improvement.

Factors Affecting Rate of Improvement from Selection

Four factors affect the rate of improvement that is possible from selection:

  • Heritability (h2)

  • Selection differential (SD)

  • Genetic association among traits

  • Generation interval (Gl)

The rate of improvement per year for a single trait can be estimated:

Rate of Improvement = (h2 * SD) ÷ Gl

If selection is based on more than one trait, the genetic association between traits becomes important.

Heritability

Heritability assigns a percentage value to a given trait, indicating what portion of the observed variation between individuals in a herd is transmitted genetically. The higher the heritability for a given trait, the greater the potential rate of genetic improvement. But since external factors can also influence development, producers must expose animals to similar environments in order to effectively compare traits for purposes of selection. Eliminating external sources of variation isolates the true genetic differences between individuals and increases the effectiveness of selection.

Average heritability estimates for some of the economically important traits in beef cattle are listed in Table 1. Actual heritability for a particular trait can be expected to vary slightly from herd to herd, depending on genetic variability within the herd and the uniformity of environment. Based on heritability estimates, selection should be reasonably effective for most performance traits. However, traits vary both in heritability and economic importance. So, just as expected rate of improvement varies according to heritability, the emphasis each trait should receive in a selection program varies according to its economic importance.

Heritability estimates for each trait, combined with that trait's economic value to a particular producer, should determine the relative emphasis each trait receives in the producer's selection program. If a trait is medium to high in heritability, the purebred producer can select for animals that are superior in that trait and expect reasonable progress. If the trait is low in heritability, little progress can be made through selection; however, considerable improvement for traits low in heritability can be generated through crossbreeding. Thus, a commercial producer improves those traits low in heritability (primarily reproductive traits) by crossbreeding while improving those traits medium to high in heritability by purchasing bulls from a purebred breeder who has been selecting for improvement in the traits desired.

Selection Differential

Selection differential for a given trait compares the average performance of selected individuals to the average of herd animals from which they were selected. For example, if average weaning weight for the herd is 450 lb, but average weaning weight of herd animals selected for breeding is 480 lb, then the selection differential is 30 lb. On average, cattle operations producing their own replacements save 30% to 40% of their heifers each year, while retaining only 2% to 5% of their bull calves. Because of these differences in replacement rates, the greatest influence on selection differential will always be from the bull's side. After several generations, up to 80% of genetic improvement in a trait is traceable to the herd sires. To accelerate the rate of genetic improvement, every effort should be made to obtain maximum selection differential for those trait(s) of greatest economic importance and highest heritability; traits that have little bearing on efficiency of production or carcass desirability are rarely emphasized.

Genetic Association Among Traits

A genetic relationship can exist between any two given traits, whereby genes favorable for the expression of one trait tend to either support or suppress expression of the other trait. So, these genetic associations can be either positive or negative. If the genetic association between traits is positive (as are associations among birth weight, preweaning gain, postweaning gain, and mature size), then selection to increase one of these traits will cause a comparative increase in the other, positively related traits. When two traits are negatively correlated, such as rate of gain and marbling, selection to increase one trait will cause the other to decrease.

There is a strong genetic relationship between the scrotal circumference of young bulls (age 12 to 15 months depending on the breed) and the age at puberty of related females (larger scrotal circumference being associated with earlier puberty in heifers). As a result, if cattle producers would like to have their replacement heifers become pregnant for the first time at an early age, they could select bulls with larger scrotal circumference to sire the heifers.

Generation Interval

The last major factor that influences rate of genetic improvement from selection is the generation interval of a herd, that is, the average age of all parents when a group of their offspring is born. Generation interval averages 4 1/2 to 6 years in most beef cattle herds. Genetic progress can be accelerated by shortening the generation interval. This is accomplished through vigorous culling of the cow herd (based on production), calving heifers as 2-year-olds, and using yearling bulls on a limited number of females.

Understanding Performance Information

Performance testing is a helpful tool that eliminates some of the guesswork involved in selection of breeding animals. Simple, raw figures on average daily gain and actual weaning weights are not very useful in bull selection. For example, if you are considering a bull and all you know is that he had a weaning weight of 600 lb, you have little to go on. He could have been raised by a heifer on drought-stricken pasture, or he could have been raised by a mature cow on lush pasture with plenty of creep feed. On the other hand, if you are informed that the bull weaned at 600 lb adjusted 205-day weight (no creep), ratioed 110 with 42 contemporaries, and his mother is a 5-year-old cow with a weaning ratio of 107 on 4 calves and an average calving interval of 365 days, then you have more information on which to make an intelligent, within-herd selection decision. This type of additional information is useful, and available from most purebred breeders.

Breeding values are determined by an animal's genetic makeup. The newest format for reporting breeding values for economically important traits is expected progeny difference (EPD). Expected progeny differences for various traits are useful only to compare the expected performance of one bull's progeny with the expected performance of the progeny of another bull of the same breed. For example, if Bull A has a weaning weight EPD of +20 lb and Bull B has a weaning weight EPD of +5 lb and they are mated to a large number of comparable cows, a 15-lb difference between the average weaning weights of their respective calves could be expected.

An accuracy value (ACC) is assigned to each EPD, indicating the reliability of the EPD. Reliability refers to a level of certainty that the EPD will not change as more offspring are tested (Table 2). Animals with more calves in several different herds will have higher accuracy values for their EPDs.

Specific traits available for comparison vary from breed to breed. Traits usually include characteristics such as birth weight, weaning weight, milking ability (expressed as pounds of weaned calf), yearling weight, hip height, scrotal circumference, and calving ease. The following are some commonly evaluated traits:

Calving Ease EPD—Ratio for calving ease, with 100 representing the average for all animals of that breed type on which data have been collected. Values greater than 100 mean there is less likelihood of calving difficulty for first-calf heifers.

Birth Weight EPD—Calf weight (lb) at birth, adjusted to a mature dam equivalent. Bulls with higher EPD values for birth weight are expected to sire calves heavier at birth than bulls with lower EPDs.

Weaning Weight EPD—Calf weight (lb) adjusted to 205 days of age and a mature dam equivalent. Bulls with higher EPD values for weaning weight are expected to sire calves heavier at weaning than bulls with lower EPDs.

Yearling Weight EPD—Weight (lb) adjusted to 365 days of age. Bulls with higher EPD values for yearling weight are expected to sire calves heavier at one year of age than bulls with lower EPDs.

Maternal Weaning Weight EPD—Weaning weight (lb) of an animal's daughters' calves. Values reflect both the milking ability of daughters and growth potential of their calves.

Maternal Milk EPD—Portion of weaning weight (lb) of an animal's daughters' calves that is due to the daughters' milking ability. Bulls with higher EPD values for maternal milk are expected to sire daughters with greater milk-producing ability than bulls with lower EPDs.

Beef breeders can now use records to mate “the best to the best” (see Figure 1). Perhaps more importantly, breeders can use this information to select the right bull to use on a particular cow or set of cows, based on their respective strengths and/or weaknesses.

Figure 1. 

Performance pedigree of an Angus bull.


Credit:

All of this information was adapted from the American Angus Association website (http://angus.org) and was used by permission.


[Click thumbnail to enlarge.]

Bull Selection

Selection of herd bulls is one of the most important decisions you will make as a cow-calf producer. The herd bull (or set of bulls) is generally considered to form half the herd because he supplies half the genetic make-up of an entire calf crop. However, in herds where replacement heifers are retained, 87.5% of the genetic makeup of each calf comes from the last three bulls used. Therefore, the importance of selecting genetically superior bulls cannot be overemphasized.

Bulls' performance information should be evaluated to reduce guesswork involved in selection. Evaluate the strengths and weaknesses of your cow herd, then select a bull that will complement your herd. (In the case of purebred herds that use artificial insemination, mating can be planned on an individual cow basis.) For example, if you are a commercial producer, your goals might be to increase or decrease frame size, increase weaning weight, minimize calving difficulty, or increase milking ability. So, by utilizing information on EPDs for those traits, you can achieve genetic progress toward your goals. Any bull that does not, on paper, appear to be of potential benefit to your cow herd should be eliminated from further consideration, regardless of price. “Bargain” bulls are seldom bargains in the long run.

One suggestion to improve accuracy when purchasing young, unproven bulls with low accuracy values for their EPDs is to use performance records for purposes of comparison. If the bull you are considering has superior EPDs to his contemporaries', then his performance should be at least as good as—if not above—the group average. (In fact, for some breeds EPDs have not yet been determined, making performance records the only objective data available.) Be aware: Performance and production records, pedigrees, and EPDs are only as accurate as the records of the breeder who reports the information.

Table 3 provides performance information on three different bulls. Which bull would you select? If your only priority is to maximize growth, then select Sire C. If your priorities are calving ease (important for heifers) and improving milk, then select Sire B. And if your priorities are to improve growth and milk while maintaining relative calving ease, then select Sire A.

Once you determine that a bull is genetically capable of helping your program, your next step is to see whether he can deliver this genetic information. At this stage, reproductive efficiency is best measured by a breeding soundness evaluation. (A more complete discussion can be found in http://edis.ifas.ufl.edu/an119.) A bull should have already passed his breeding soundness evaluation or the seller should be willing to guarantee that he will—before you proceed with the selection process.

Visual selection is important once the bull has met the previous criteria. Structural soundness is essential if bulls are to travel the necessary distances to keep up with cows and then be able to mount them (especially if bulls are expected to breed a large number of cows within a short time interval). Be aware of the following indications of unsoundness: rear legs that are too straight (post legs); rear legs too close at the hocks, with too much angle (cow hocked); corns and abnormal hoof growth (evidence of founder).

Muscling can also be evaluated. The bull should be well-muscled, which is plainly evident in a large, bulging forearm and thickness in the round. Terms such as long, smooth, or flat are frequently used to describe muscling. These are misleading. Since all bulls' muscles attach to their skeletons at the same places, “length” of muscle would depend strictly on frame size. And “flat” muscles would be unlikely since muscle fibers are round, and bundles of these fibers form the muscle tissue. “Smooth” muscling might actually mean that the animal is covered with an outside layer of fat, or that muscling is scant. Don't be misled by meaningless terms when someone is trying to sell you a bull!

Other traits such as frame size, breed type, and freedom from excessive fatness can be evaluated visually as well. For example, if calving ease is a major consideration for the herd, evaluate shoulder structure and size of the head and neck. Avoid bulls with coarse or massive shoulders.

DNA marker information Today, in addition to weights, weight ratios, and EPD data for the weight and carcass information, there often will be data available from breeders of Angus and other breeds regarding DNA marker information on the bulls that they are offering for sale. This information is generally on carcass-related traits that cannot be measured directly on the live animal such as marbling and tenderness. More recently, information on feed efficiency markers has become available. Feed efficiency is very difficult and expensive to measure on farm and is becoming of greater importance than ever now with very high corn prices.

DNA markers from one to as many as four or more loci (locations on specific chromosomes) have been identified as having an impact on the various traits (tenderness, marbling, feed efficiency) and at each of these loci, one allele (gene) has been identified as having a desirable effect (more marbling for example) and the other allele as having a negative or neutral effect. Sires then have their DNA evaluated to determine which alleles they have at each of the loci that have been identified as having an effect on the trait. The total number of desirable alleles that an individual sire possesses is considered his number of “stars.” Thus, if there are three loci identified as affecting the trait and the sire is labeled as a “Six-Star” bull, that means that he is homozygous for the desirable allele (has two desirable alleles) at each of the three loci. One must be careful, however, to not place too much emphasis on the number of “stars” that any given bull has relative to that of another. This is because there are other genes that affect each of the traits and a bull with two stars might be just as good genetically for tenderness, for example, as a bull that has six stars. On the average, however, we would expect the “six-star” bull to sire progeny with better tenderness than the “two-star” bull if the markers that have been identified and tested for account for a substantial proportion of the variation in tenderness.

If you are purchasing a bull in a sale, make your decision about which bulls you like and how much you are willing to pay before the bidding starts. Don't sit back to see how animals are going to sell while the best bulls are selling. Don't rush through the entire selection process in the time it takes an auctioneer to sell a bull. Study the performance information ahead of time, and arrive at the sale site early enough to allow yourself adequate time to evaluate the bulls.

Sire selection extends beyond the initial purchase. Observe the bull closely during the first few weeks of breeding season to see if he is willing and able to mate with the cows. Bulls with high libido (sex drive) and high fertility will sire the early calves. Also observe the cows for a return to heat after mating; you need to know whether the bull is settling them. Your final step is to annually evaluate each bull's progeny. If calves demonstrate acceptable performance, retain the bull. If his calves are unacceptable, you should replace the bull.

Selecting a Breed or Breed Type

Producers always have strong feelings on the merits of their favorite breeds of cattle. However, no single breed excels in all traits. It is important to know relative strengths and weaknesses of the various breeds so that you can plan mating systems in which breeds will complement each other.

Knowing general characteristics of breed types will help you in planning. British breeds (those that originated in the British Isles, such as Angus and Hereford) generally excel in fertility, good disposition, and finishing at medium weights. Continental breeds (breeds from Europe, such as Simmental and Charolais) are larger, grow faster, and produce leaner carcasses unless fed to heavier weights. Brahman and Brahman-derivative breeds have better heat tolerance, calving ease, and longevity.

You should select a breed (or combination of breeds) to use in your beef program based on the following:

  • Goals of your operation

  • Marketability in your area

  • Cost and availability of good seedstock

  • Adaptability to environmental and nutritional conditions

  • Breed “complementarity” (selection of breeds whose superior traits complement each other in a crossbreeding program)

  • Personal preference

Table 4 lists some cattle breeds, grouped according to size and type (beef, dual purpose, and heat tolerant). It is very important that at least one heat-tolerant breed be selected. At least 25% Brahman breeding in the brood cow herd is necessary for nearly all production systems in Florida. Alternatively, one of the heat-tolerant Bos taurus breeds (such as Senepol or Tuli) can be used in place of Brahman. However, a particular advantage of the Bos indicus (Brahman) crossbred cow is her ability to restrict the birth weight of her calves and to calve without assistance.

Table 5 lists some breed crosses evaluated for production by growth rate and mature size, lean-to-fat ratio, age at puberty, and milk production. It should be emphasized that the greater the size and level of milk production, the greater the breed's nutritional requirements. Therefore, the larger, heavier-milking breeds should not be utilized unless you have the resources to meet their increased requirements through supplemental feeding or improved pastures.

A sire breed in a crossbreeding program might have the following characteristics: rapid growth rate, moderate-to-thick muscling, and adequate calving ease. A dam breed might have these characteristics: high fertility, good milking ability, and small-to-medium mature size. Most breeding programs must produce both replacement females and steer calves destined for the feedlot. Because no single breed possesses all traits necessary for producing both desirable brood cows and feeder steers, some compromises must be made when selecting breeds for a crossbreeding program.

Crossbreeding for the Commercial Producer

Crossbreeding is a system that mates cattle of different breeds, or breed compositions. It can be an effective method for improving beef production. There are two primary reasons to use crossbreeding: (1) breeds have characteristics that complement each other, and (2) heterosis, or hybrid vigor. When crosses are made, one breed's strengths can offset the other's weaknesses. Since no single breed is superior in all traits, a planned crossbreeding program can significantly increase herd productivity (Figure 2). However, it should be recognized that complementarity between breeds cannot be effectively utilized in rotational crossbreeding systems, the type most commonly used. Breeds comparable in birth weight, growth rate, mature size, and milk production should be selected for use in rotational systems to ensure uniformity in the calf crop.

Figure 2. 

Crossbreeding is an effective way to increase the weight and improve the quality of feeder calves.


[Click thumbnail to enlarge.]

Heterosis for a trait is the increase (%) in productivity of crossbred offspring over the average of the breeds that produced them. Heterosis is highest for less heritable traits (such as reproductive traits), and lowest for highly heritable traits (such as carcass traits). Crosses of British breeds with Brahman cattle (or other Bos indicus breeds) yield much higher levels of heterosis than do crosses of British breeds with other Bos taurus breeds.

Table 6 indicates two types of heterosis, individual and maternal. Individual heterosis refers to improved growth traits of the crossbred calf; maternal heterosis refers to improved maternal ability (fertility, milking ability, etc.) of the crossbred dam. Maximum improvement in a trait due to heterosis occurs when F1(two-breed) crossbred dams are bred to sires of a third breed. The total increase in annual production, per cow, can be as much as 40% for Bos indicus x Bos taurus crossbred cows over purebred cows under the same conditions.

Selection should be based on highly heritable traits, such as growth, while crossbreeding enhances the less heritable traits, such as reproduction. Superior purebreds are the backbone of crossbreeding programs. Even if you use crossbreeding, you still need to buy good bulls.

The benefits of crossbreeding can be very impressive because its effects are cumulative. Any single trait might seem to be of minor importance, but when increases in calving rate, livability and growth rate are evaluated together, substantial improvement over straightbred cattle is evident (see Table 6).

Crossbreeding Systems

Crossbreeding systems must be planned individually for each operation according to herd size, potential market, level of management, and available facilities. A long-term plan is essential to gain maximum benefits from crossbreeding. This section lists some advantages and disadvantages of various crossbreeding systems.

Two-Breed Terminal Cross. This system uses straightbred cows with a bull of a second breed. The cross is considered “terminal” because all crossbred offspring are market animals. An example would be Angus cows bred to a Charolais bull.

With this system, replacements must either be bought from another source, or else part of the herd (perhaps heifers and young cows) must be bred to Angus bulls in order to generate replacement heifers. In addition to this problem of obtaining replacements, a two-breed terminal cross system precludes the benefits of maternal heterosis, so females might not be sufficiently adaptable to Florida conditions. This can be a workable system for smaller herds.

Three-Breed Terminal Cross. This system uses F1 (two-breed cross) cows with a bull of a third breed. An example would be Brahman x Angus F1 cows bred to a Hereford or Charolais bull. It produces near maximum heterosis in both cow and calf.

This is an excellent system because hybrid vigor for growth rate and maternal ability are both realized. However, 40% to 50% of the herd must be maintained as straightbred cows in order to generate enough F1 replacement females for the terminal cross. While the use of sexed semen that will produce only heifer calves when used on the straightbred cows to generate the replacements might be able to reduce the percentage of straightbred cows required, it is likely that the F1 females will need to be purchased from other producers. You will find Brangus-type replacement females (crossbred animals with both Angus and Brahman ancestry) to be more available at reasonable prices than true F1 cows, although they will likely yield less heterosis.

Two-Breed Rotation (or Crisscross). This is a simple crossbreeding system involving two breeds and two breeding pastures. The two breeds are mated, and female replacements are saved from the crossbred offspring to breed back to one of the parent breeds (backcross). In each succeeding generation, replacement females are bred to bulls of the breed opposite that of their sire (Figure 3). Two herds are necessary, one to be mated with each breed of bull. Replacement bulls are the only animals that would originate from outside the herd. The main drawback of two-breed rotation is that it maintains only about 66% of the potential heterotic response. To its advantage, however, this system is easily managed, does not require large numbers, and utilizes crossbred dams. In fact, if AI is possible, the cows could still be managed in one herd. In addition, the system generates its own replacement females.

Figure 3. 

Two-breed rotational system (crisscross).


[Click thumbnail to enlarge.]

Selection of breeds for this system, as well as any other, is very important. The two breeds chosen should be comparable in birth weight, mature size, and milk production. This will minimize calving difficulty in first-calf heifers, and simplify management. Using Brahman with the Angus or Hereford breeds in two-breed rotation will produce productive cattle. However, the Brahman and the Hereford or Angus are not similar in age at puberty, and the calves from this two-breed rotation will vary considerably in ear length and other Brahman characteristics. Hereford x Brangus, Angus x Braford, and Senepol x Angus are possible rotations that will produce adaptable replacement heifers and more uniformity of type. Herd size must be large enough to utilize at least two bull breeding units (20 to 30 head breeding-age females per unit).

Three-Breed Rotation. This system follows the same basic pattern as two-breed rotation, except it requires three breeds (see Figure 4) and does not include a backcross. In this rotational system, you have to maintain three herds or breeding groups. The first herd is bred to bulls of Breed A; female offspring from this herd are used as replacements for the second herd. Bulls of Breed B are mated to cows in the second herd; and females from this mating are used as replacements for the third herd. This third group is bred to bulls of Breed C; and heifers from this mating are used as replacements for the first herd. The sequence continues, using the same three breeds of bull in the same pattern of rotation.

Figure 4. 

Three-breed rotational system.


[Click thumbnail to enlarge.]

Three-breed rotation can maintain a higher level of hybrid vigor than the two-breed system (theoretically, 87%). Rotation of Brahman x Angus x Hereford has been effectively utilized in Florida for many years. Mating yearling heifers to Brahman bulls should be avoided, however, to help circumvent calving difficulty. As with two-breed rotation, the breeds selected should be comparable in birth weight, mature size and milk production to improve uniformity of the resulting calf crop.

One advantage of three-breed rotation is that replacement heifers are produced on the ranch, eliminating the need to purchase replacements. A disadvantage is that herd size must be at least three bull breeding units; otherwise, artificial insemination should be used. (AI could also eliminate the problem of maintaining three separate herds.) Uniformity of calves for marketing can be a problem in small herds.

Rotational-Terminal Cross Combination.This program combines rotational and terminal cross systems. Breeds A and B are used in a two-breed rotation, producing their own replacements (Figure 5). Older and less productive cows are taken from these two crossbred herds and placed in a third breeding group. This herd is mated to a terminal-sire breed (Breed C) and all of the terminal cross offspring are marketed. In this manner, a producer can take advantage of the terminal cross to maximize hybrid vigor without having to purchase female replacements from an outside source.

Figure 5. 

Combination program using rotational and terminal cross systems.


[Click thumbnail to enlarge.]

A practical method of utilizing this system is to use bulls of Breeds A and B during the first 45 days of breeding season to sire the replacement heifers, then pull these bulls and replace them with terminal cross bulls (Simmental, Charolais, Limousin, etc.) to use for the remainder of the breeding season. With this system, the oldest heifers are kept as replacements, which increases their chances of conceiving as yearlings; and the younger heifer calves (which are heavier because they were sired by the larger, terminal cross bulls) are sold. This system requires either a fairly sizable herd (at least two bull breeding units) or utilization of AI. Uniformity of calves for marketing can be a problem in small herds.

Modified Crossbreeding

For many herds, due to the level of management required or due to a lack of facilities, intricate crossbreeding systems are not feasible. However, with some modification it is still possible to implement some basic crossbreeding principles. Here is what you can do to simplify the traditional systems.

Purchase Crossbred Females. This is the simplest and fastest method of achieving maximum hybrid vigor. For example, two-breed cross females can be purchased and bred to a terminal sire of a different breed (as in the three-breed terminal cross), maximizing both individual and maternal hybrid vigor. The producer needs an available supply of high-quality, disease-free F1 females. For the small 1- or 2-bull herd, this is often the most desirable program, since precious resources are not tied up developing replacement heifers.

Use Multi-Year Bull Breed Rotation. This involves using one bull for a series of years, then rotating to a different breed of bull. Only one breeding pasture is required, and replacement heifers are generated within the herd. This system sacrifices some hybrid vigor compared to a two breed rotation, but it is simple enough to make it practical for more producers. However, the Brahman should not be used as one of the breeds in this system because calves exhibiting excessive levels of Brahman ancestry can result. A rotation of Brahman-derivative breeds (e.g., Brangus x Braford, or Brangus x Hereford) can yield satisfactory results by using Brangus bulls for 2 to 3 years, and then replacing them with Braford or Hereford bulls for 2 to 3 years.

Use Composite Breeds. The development of composite breeds is currently the focus of several research programs. Their objective is to develop a method for maintaining the benefits of hybrid vigor (heterosis) without having to maintain several breeding herds or use several sire breeds. Such developments will be of greatest benefit in small herds, where crossbreeding systems are difficult to maintain.

Some success has been reported toward development of breed combinations that are efficient to produce with desirable carcass features. The unanswered question is whether these composite animals (particularly the Brahman-derivative) can be mated over several generations and still maintain their heterosis and productivity. Using composite breeds as "straightbreds" could be an alternative in the future.

Do Not Use a Multi-Breed Bull Pasture System. This system should not be used due to excessive variability among the calves produced.

Tables

Table 1. 

Average heritability (h2) estimates for some economically important traits in beef cattle.

Heritable Trait

h2

Level, h2

Twinning

3%

Low

(h2 < 20%)

Calf survival ability

5%

Conception rate

10%

Calving interval

10%

Gain, birth to weaning

30%

Medium

[20% < h2 < 40%]

Weaning weight

30%

Pasture gain

25%

Birth weight

40%

High

[h2 > 40%]

Feed efficiency

40%

Yearling body length

40%

Yearling weight

40%

Mature weight

50%

Carcass grade

40%

Fat thickness (12th rib)

45%

Yearling hip height

60%

Rib eye area

50%

Table 2. 

Accuracy valuesa indicate levels of reliability for an animal's EPDs.

Reliability

Low

Medium

High

ACCa

<.50

.50-.75

.75-1.00

aAccuracy value (ACC) of the expected progeny difference (EPD) for a trait.

Table 3. 

Example performance information on various bulls.

Sire

Calving Ease, %

Birth Weight, lb

Weaning Weight, lb

Yearling Weight, lb

Maternal Milk, lb

EPD

ACC

EPD

ACC

EPD

ACC

EPD

ACC

EPD

ACC

A

97

.70

+1.6

.70

+20

.85

+25

.80

+22

.75

B

105

.70

-2.5

.75

-2

.90

+7

.85

+25

.80

C

87

.70

+12.0

.72

+40

.80

+62

.75

-5

.70

Table 4. 

Grouping of some cattle breeds, by functional type.

Smaller Beef

Smaller Dual Purpose

Bos indicus

Brahman Derivative

Larger Beef

Larger Dual Purpose

Heat-Tolerant

Bos taurus

Angus

Amerifax Boran Barzona Belgian Blue

Beef Friesian

Romosinuano

Beefalo Milking Shorthorn Brahman Beefmaster Blonde D'Aquitaine Braunvieh Senepol
Florida Cracker Normande Gyr Braford Charolais Gelbvieh Tuli
Hereford Pinzgauer Indu-Brazil Brahmaine Chianina Maine Anjou  
Longhorn Red Poll Nellore Brahmanstein Limousin Simmental  
Piedmontese Salers Sahiwal Brahmousin Marchigiana    
Polled Hereford Tarentaise   Bralers      

Red Angus

Welsh Black  

Brangus

     
Shorthorn     Charbray      
      Gelbray      
      Pinzbrah      
     

Red Brangus

     
      Santa Gertrudis      
      Simbrah      
Table 5. 

Some breed crosses evaluated for productiona, by trait.

Breed Groupb

Growth Rate and Mature Size

Lean-to-Fat Ratio

Age at Puberty

Milk Production

Jersey-X

+

+

+

+++++

Hereford-Angus-X

++

++

+++

++

Red Poll-X

++

++

++

+++

South Devon-X

+++

+++

++

+++

Tarentaise-X

+++

+++

++

+++

Pinzgauer-X

+++

+++

++

+++

Sahiwal-X

++

+++

+++++

+++

Brahman-X

++++

+++

+++++

+++

Brown Swiss-X

++++

++++

++

++++

Gelbvieh-X

++++

++++

++

++++

Simmental-X

+++++

++++

+++

++++

Maine Anjou-X

+++++

++++

+++

+++

Limousin-X

+++

+++++

++++

+

Charolais-X

+++++

+++++

++++

+

Chianina-X

+++++

+++++

++++

+

a+ = Low; +++++ = High

bX=Herford-Angus on dam side; sire breed is listed first.

Source: University of Nevada-Reno and USDA. 1988. Crossbreeding Beef Cattle for Western Range Environments. TB-88-1. University of Nevada, Reno.

Table 6. 

Heterosis levels for some traits in beef cattlea.

Trait

Types of Cross

Bos taurus x Bos taurus

Bos indicus x Bos taurus

Individual Heterosis, %    

Birth weight

2.4

11.1

Weaning weight

3.9

12.6

Postweaning gain

2.6

16.2

Maternal Heterosis, %

   

Calving rate

3.7

13.4

Calf survival

1.5

5.1

Birth weight

1.8

5.1

Weaning weight

3.9

16.0

aAdapted from: Cundiff, L.V., L.D. Van Vleck, L.D. Young, K.A. Leymaster, and G.E. Dickersen. 1994. Animal breeding and genetics. In: Encyclopedia of Agricultural Science. Volume 1. pp 49-63. Academic Press Inc.

Footnotes

1.

This document is AN116, one of a series of the Animal Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date November 2001. Revised October 2007. Reviewed September 2012. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Bob Sand, associate professor and Extension livestock specialist Department of Animal Sciences; Mark Shuffitt, livestock Extension agent Marion County; Pat Hogue, county operations Extension agent Okeechobee County; and Tim Olson, asssociate professor and animal breeding, Department of Animal Sciences; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.