2 sire breed (rotation) + 1 sire breed (terminal), Maternal sires and terminal sires needed, Gosey, J. Replacement females leave the location of their birth to be mated to sires with different breed composition, A rotational crossbreeding system in which sire breeds are not used simultaneously, but are introduced in sequence, A crossbreeding system in which maternal-breed female are mated to paternal-breed sires to efficiently produce progeny that are especially desirable from a market standpoint. Composite populations developed by mating like animals resulting from two or more breed crosses provide an alternative to more complex crossbreeding systems. Crossbreeding and GMO (Genetically Modified Organism) are two types of techniques used in agriculture to develop animals and plants with desired traits. the remaining breed. The parent organisms must be genetically compatible and may be from different varieties or closely related species. A relatively high level of heterosis is maintained, usually 50 percent or greater depending on the number of sires used and the sequence in which sire breeds are used. This yields more heterosis than rotating breeds with each new bull or every two years. JavaScript seems to be disabled in your browser. When composites are used sires and dams do not differ, thus no breed complementation is offered. In a static terminal sire crossing system (Figure 5), straightbred females of breed A are mated to straightbred males of breed A to produce straightbred replacement females. When crossed, Brahman British cattle produced from this mating are generally expected to be maternal animals adapted to hot and humid climates. A variety of crossbreeding systems are available for breeders to use in their genetic improvement programs. Discounting the potential loss of heterosis due to accumulated inbreeding, retained heterosis can be calculated by squaring the fractional contribution of each breed, summing the squared values and subtracting from one. Figure 9.2 shows four . University of Missouri Extension is an equal opportunity/access/affirmative action/pro-disabled and veteran employer. This phenomenon allows a breeder to blend the superior traits of one animal with the superior traits of another animal into their crossbred offspring. What is crossbreeding - definition, mechanism, meaning 2. Choice of breeds becomes an important consideration, as the number of breeds included in a rotation is increased. System which differs from static crossbreeding programs because it is modified to produced replacement females. Maternal heterosis is the increase in average production observed in crossbred females compared to straightbred females. This will result in lower production per breeding female than will be seen in crossbred females because 0 percent maternal heterosis results. Additional crossbreeding opportunities are available to the producer with a slightly larger beef herd. All progeny, both male and female, are produced for slaughter. An example of an unfavorable result of heterosis is an increase in fatness of crossbred calves. Prediction of weaning weight per cow exposed is similar to calculation above, except individual heterosis is 8 percent and maternal heterosis is 19 percent: = [(0.5 (396) + (0.25 (349) + (0.25 351)] (1 + 0.08) (1 + 0.19). Which mating system results in maximum breeding by a superior male? After several generations of using this cross, hybrid vigor will stabilize at 67 percent of potential individual and direct heterosis with an expected 16 percent increase in pounds of calf weaned. In the hot, humid Gulf Coast, 50:50 ratios of Bos indicus to Bos taurus inheritance may be optimal. The composite breeding system combines desirable traits of how many breeds of cattle? For example, salmon fish have been genetically engineered to grow larger, and cattle have been engineered to be resistant to mad cow disease. Individual heterosis is maximized because the maternal line (Angus and Hereford) has no common breed composition with the terminal sire (Charolais). They should be mated to the bulls with which they are least related. The breeds used in the two-breed rotation must still be selected for the criteria specified in the rotational programs. Yorkshires have acceptable rates of gain in muscle mass and produce large litters, and Durocs are very . General Considerations * Rotational systems generally make more effective use of heterosis. GMOs are produced to optimize agricultural performance, reduce susceptibility to disease, and produce key pharmaceutical ingredients. Furthermore, management of breeding systems where multiple breeding pastures is required poses another obstacle. the female using mechanical means rather than by natural service. In fact, if discounts for yield grade differences are similar to those for USDA quality grade, in temperate environments, cattle that are half-Continental and half-British have a much better chance of hitting profitable targets for retail product percentage, marbling and carcass weight. Adapting data for weaning weight from Notter, 1989 (Beef Improvement Federation Proceedings), Angus were 432, Hereford 435, and Charolais 490 pounds. The pollen grains of one plant breed are deposited on the stigma of the other plant breed to create a cross. Crossbreeding is also an important part of commercial production systems because of the improvement in efficiency from heterosis and the potential to exploit differences between breeds or lines. Throughout this publication, % heterosis will be in reference to an F1 (first-generation cross) with 100 percent heterosis. Source: GreenFacts. No breed complementation is obtained from a rotational cross. To take advantage of breed complementation, breeds with good maternal ability and milk production would be used in a dam line and be mated to large framed, fast growing terminal sire breeds. This system yields slightly more individual heterosis than the two-sire, two-breed system but slightly less maternal heterosis. A crossbreeding system combining a maternal rotation for producing replacement females with terminal sires for producing market offspring Composite (Synthetic) Animal A hybrid with a least two and typically more breeds in its background. After the first four years, cows sired by breed A bulls are mated to breed B bulls and vice-versa. A high percentage of straightbreds are needed to produce straightbred and F1 replacement females, sacrificing the benefits of individual and maternal heterosis. What is the difference between crossbreeding and GMO - comparison of the main differences, Key Terms: Animals, Crossbreeds, Genetically Modified Organisms (GMOs), Hybrid Vigor, Plants, Traits. A breed refers to an interbreeding group of organisms within a species with a common appearance and behavior. Management of matings for this system can also be somewhat complex. Which crossbreeding system produces replacement females through the rotation and produces crossbred offspring? The answers to these questions will impact the type of crossbreeding system that best fits with operational goals. Cost and availability of these resources need to be considered. After three generations, breed composition stabilizes at approximately ? Again, no breed complementation is available. Only one breeding pasture is needed, labor and management are minimized, and progeny produced are highly uniform and marketable. Nebraska, Lincoln, NE. Since a single bull is used, not all matings can be optimal as in the two-breed rotation. * Genetic potential for USDA quality and yield grades can be optimized more precisely in cattle with 50:50 ratios of Continental to British inheritance than in cattle with higher or lower ratios of Continental to British inheritance. The hybrid vigor from this mating can be calculated with the following equation: (Crossbred performance average Straightbred performance average) Straightbred performance average. Nature News, Nature Publishing Group, Available here . Unfortunately, it also requires multiple breeding pastures or artificial insemination (AI) to ensure correct matings resulting in maximum heterosis. Considerations related to developing versus purchasing replacement females apply to operations of any size, but profitability of heifer development is generally affected by scale. The agricultural crops are the most common examples of GMOs. Static crossing systems work well in species with high reproductive rates (poultry, swine) but less well in species with lower reproductive rates (cattle). Enter and space open menus and escape closes them as well. GMO: GMOs can be introduced with genes of a different species. In cow herds, producers need to keep an eye on breed compatibility for traits such as birth weight to minimize calving difficulty, size and milk production to stabilize feed requirements. A three-breed rotation initiated again with breed A cows would have a breed sequence for sires as shown in Table 3, with the subscripts representing different bulls of breeds A, B, and C. This single-sire rotation is expected to yield 77 percent of maximum individual and 60 percent of maximum maternal heterosis. Before implementing a crossbreeding program, a producer needs to have well-defined goals for the operation. In a two-breed rotation, females sired by breed A are always mated to males of breed B. Which of the following is NOT considered an advantage of embryo transfer? Because replacement heifers are purchased, a source of quality crossbred females is essential. X-Cross is short for Extended Cross. If Hereford bulls with average genetic merit were mated to average Angus cows, crossbred calves would be expected to weigh 5 percent more than the average of the pure breeds in the cross: [( Angus weight) + ( Hereford weight)] (1 + Individual Heterosis), = [(0.5 432) + (0.5 435)] (1 + 0.05). When carcass and meat traits are considered, breeds that excel in retail product percentage produce carcasses with marbling levels below optimum and carcass weights above optimum. used mostly by commercial breeders; males and females coexist throughout the breeding season or year round. weaned over 9.4 years) or Herefords (2,405 lbs. Sire rotation is a common crossbreeding system. At the same time, genetic engineering gives GMOs some enormous and elite properties. Individual and maternal heterosis for beef cattle. As partial compensation for the management required, AI offers the advantage of making available many sires with outstanding genetic merit, a situation that would not be economical for most commercial producers for use in natural service. - Extension Animal Scientist Dale ZoBell, Ph.D. - Extension Beef Specialist One of the most powerful tools available to cattle producers to improve the efficiency of production in a herd is the use of crossbreeding. Use of sex-sorted semen for artificial insemination can facilitate this, allowing targeted production of replacement heifer candidates from a selected portion of the cow herd. Expected performance is very similar for the two systems. The value of 479 pounds of calf weaned per cow exposed for the crossbred cows raising crossbred calves compares with an average genetic merit of the combination without heterosis of 373 pounds ( the genetic merit of Charolais plus the genetic merit of each Angus and Hereford). As more breeds contribute to the composite, retained individual and maternal heterosis increases. When using two sires, one available option is to use part of the cow herd in a terminal cross. Genetically modified plants can also mature more quickly and can tolerate drought, salt and frost. Likewise, they must decide on practices that affect productivity and returns. The two-breed rotation is an effective and relatively simple crossbreeding system that takes advantage of individual and maternal heterosis (Figure 3). What method of breeding can increase conception rates by five to ten percent? Of course, use of sex-sorted rather than conventional semen for this purpose minimizes the number of steer calves that are produced from maternally-oriented sires. This system is used frequently in Western range states. Enhanced production from the crossbred female is the primary benefit from a planned crossbreeding system.