modified static crossbreeding system definition

Use of all heifers calves from the two-breed rotation as replacements can be limiting if death loss is high or if the proportion of calves which are female is low in a particular year. Crossing: Crossing refers to the pairing of two different species, variants or races. An example of an unfavorable result of heterosis is an increase in fatness of crossbred calves. 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. Crossbreeding: Crossbreeding can be done between different breeds of the same species. In market animals, breed compatibility for production traits is most important. Originally written by Samuel Plank, former Graduate Research Assistant, Animal and Dairy Sciences; Jane Parish, PhD, Professor and Head, North Mississippi Research and Extension Center; and Trent Smith, PhD, Associate Professor, Animal and Dairy Sciences. On the other hand, intergenerational variation can be quite large in rotational crossing systems, especially if breeds that differ greatly are used. Genetics is the science of heredity and variation. Straightbred females of breed A are also mated to bulls of breed B to produce F1 crossbred females (BA). Systems using one and two bulls are described. Biological type is significant because females are being retained that are sired by both Breeds A and B. In this publication, efficient alternative crossbreeding systems are presented for use by commercial cattle producers with small herds. The simplest example of a rotational system is the two-breed rotation or criss-cross system (Figure 2). What method of breeding is used to develop specialized "lines" of animals? Choosing a bull of a terminal sire breed also results in breed complementation. This system crosses Breed A females with Breed T sires to produce a crossbred animal that is half Breed A and half Breed T and known as an F1. Heterosis Heterosis can have substantial effect on profitability. Crossbreeding Systems for Small Herds of Beef Cattle. A dependable supply is needed if they are to be purchased. The three-breed rotation can be used with fewer cows; however, bull expenses per cow will be greater. The three-breed rotation is very similar to the two- breed rotation with another breed added. For example, Breed A averages 610 pounds at weaning, and Breed B averages 590 pounds at weaning. Several questions need to be asked. All male calves from this part of the system are sold while female calves are retained as needed for replacements. Possibilities for within herd production of crossbred replacement heifers include the use of AI on a fraction of the cows, something not always within the management capabilities of some producers; use of a breed of bull on purchased purebred heifers to produce cows for a terminal cross, which also involves purchase of a fraction of the replacements plus use of at least two breeds of sire; or use of a rotational crossing system either in combination with a terminal sire or as a stand-alone system. Behind Composite Breeds. Expected individual heterosis is 70 percent of maximum and expected maternal heterosis is 54 percent of maximum. * 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. In such a system, sires used for artificial insemination could be selected with emphasis on maternal traits. In a three-breed rotation, hybrid vigor stabilizes at 86 percent of potential individual and maternal hybrid vigor, and a 20 percent increase in pounds of calf weaning weight per cow exposed over the average of the parent breeds is realized. 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. Before implementing a crossbreeding program, a producer needs to have well-defined goals for the operation. Assuming that, as purebreds, 85 of 100 cows exposed deliver a live calf and 95 percent of calves born survive to weaning; then weaning weight per cow exposed would be 349 pounds for Angus, 351 pounds for Herefords and 396 pounds for Charolais. This system is simple in that only one breeding pasture is used, and only one breed of sire is maintained. Heterosis or hybrid vigor is an advantage in performance of crossbreds compared to the average performance of the parental breeds. Females sired by breed B are always mated to breed A (Figure 5). These values compare with 91 percent of maximum individual heterosis and 70 percent of maximum maternal heterosis for a system with no incorrect matings. Depending upon the circumstances of the operation, the benefits may not outweigh the cost in using a four-breed rotation in place of a three-breed rotation. In addition, management and labor requirements increase because of the additional complexity of using three breeds over two. The terminal system works for herds of all sizes. The resulting interspecific F1 hybrid can have intermediate traits from both parent plants. A little further north (i.e., Southeast Oklahoma, central Arkansas, Tennessee and parts of North Carolina), 25:75 ratios of Bos indicus:Bos taurus inheritance may better suit needs. The crossing of plants is carried out by cross-pollination. Commercial cattle producers face input cost management decisions every year. For example, if the optimum level of Bos indicus germplasm is 25% for a specific environment, the contribution of Bos indicus can be maintained at 25% in a composite population. A breed refers to an interbreeding group of organisms within a species with a common appearance and behavior. Such a system should be used to take advantage of breed complementarity and heterosis while also fitting the herd size and resources of the operation. Composites usually incorporate a combination of breeds, each of which contributes a characteristic desirable for good performance or environmental adaptation. Again, breed complementation is available because the sire and dam lines can be chosen for their strengths in contribution to the cross. Period 1. The rotaterminal system is more sensitive to management than are the other systems. Crossbred cattle at the University of Missouri South Farm Beef Research and Teaching Unit.Crossbreeding in commercial beef cattle production improves efficiency through heterosis and breed complementation (Figure 1). This technique is known as cross pollination. 1991. This definition corresponds closely to the definition of a H-W population with less strict random mating requirements. A minimum of three bulls are required to efficiently operate a three-breed crossbreeding program which produces its own crossbred replacement heifers using natural service. Terminal crossbreeding is a breeding system used in animal production. Both individual and maternal heterosis are less than maximum because of the common breed composition of sire and dam. Management considerations are important if the producer is to provide replacement heifers from within his own herd. Maximum heterosis (100 percent) would be expressed by progeny resulting from first crosses of two breeds and no heterosis expressed by progeny resulting from matings within a pure breed. Here is an example: Design 9. It involves two (different) breeds of animal that have been crossbred.The female offspring of that cross is then mated with a male (the terminal male) of a third breed, producing the terminal crossbred animal.. Breeding scheme for a three-breed rotational crossbreeding system. This program is appropriate for herds of all sizes because only one sire breed is used, just one breeding pasture is needed, and replacement females are purchased. Individual and maternal heterosis is yielded by this part of the system at the same rate as that for a two-breed rotation. Which of the following is a complex solution outside the cell nucleus contained by a cell membrane? The agricultural crops are the most common examples of GMOs. The genetic merit of the calf would be calculated as the genetic merit of the Charolais plus the genetic merit of the Angus and plus the genetic merit of the Hereford: [ Charlois + Angus + Hereford] (1 + Individual Heterosis) (1 + Maternal Heterosis), = [(0.5 490) + (0.25 432) + (0.25 435)] ( 1 + 0.05) (1 + 0.08). Expected performance is very similar for the two systems. A crossover design is said to be strongly balanced with respect to first-order carryover effects if each treatment precedes every other treatment, including itself, the same number of times. The composite breeding system combines desirable traits of how many breeds of cattle? After the first four years, cows sired by breed A bulls are mated to breed B bulls and vice-versa. The two-breed terminal system is the most basic crossbreeding system available (Figure 1). The youngest 60 to 65 percent of the cow herd is in a single-sire two-breed rotation. GMO: GMO (genetically modified organism) refers to an organism whose genetic material is modified by genetic engineering. Whenever possible, cows sired by breed A bulls should be mated to breed B bulls, cows sired by breed B bulls should be mated to breed C and cows sired by breed C bulls should be mated to breed A. Defined as the difference between the average of reciprocal F1 crosses (A x B and B x A) and the average of the two parental breeds (A and B) mated to produce the reciprocal crosses, heterosis was found in one study to increase weaning weight per cow exposed 23%. Which of the following types of cell division results in two identical daughter nuclei? This yields more heterosis than rotating breeds with each new bull or every two years. The heterosis gained from adding an additional breed must be greater than the loss of average genetic merit due to adding a breed which is poorer than those used to initiate the system. Regardless of whether females are produced in a static crossing system, rotational crossing systems or composite populations, breeders can take advantage of complementarity among breeds (Figure 5) by terminal crossing. Some matings that yield less than maximum heterosis will occur in years three and four. For example, older cows from the Hereford-Angus two-breed rotation would be mated to bulls from a terminal sire breed. What is the difference between culture and lifestyle? Although not maximized in all the calves, some individual and maternal heterosis contributes to the performance of all calves produced. Crossbreeding in commercial beef cattle production improves efficiency through heterosis and breed complementation (Figure 1). In general, a breed selectively reproduces only within the group. When viewed from this perspective, operations may find that their real costs of replacement heifer development exceed the market value of the replacement heifers. What is the material found in the nucleus which forms chromosomes? All rights reserved. However, this system forfeits the considerable advantages of maternal heterosis from crossbred dams. Management of matings for this system can also be somewhat complex. Which system is the mating of animals of different breeds? Mating animals of different breed backgrounds can enhance carcass traits, growth rates, and reproductive performance. 1. One breed of sire is used for 4 to 6 years, and then the sire breed is changed. Heterosis is particularly strong for . Cross- breeding can be done by cross-pollinating two different strains of plants of the same species. The last consideration is size of cowherd. First, breeds used to initiate the rotation should be the best available for your production system. Management in a single- or multiple-sire situation is straightforward. Decreases time and supervision of female herd. Pen mating is mostly used by which of the following? A three-breed rotaterminal system provides breed complementation in the terminal mating, which involves about the oldest 40 percent of the cow herd. Initially, all cows are of breed A. Legal | Ethics Line | Policy about commercial endorsements | DAFVM | USDA | eXtension | Legislative Update: Miss. Source: GreenFacts. Progeny resulting from this third generation are mated to Angus bulls and this cyclical pattern continues. As more breeds contribute to the composite, retained individual and maternal heterosis increases. Heterosis increases as number of foundation breeds increases. No single breed excels in all important beef production traits. Choice of a system should also depend on the level of management commitment you are willing to make and the size of your herd. Code Ann. Maternal heterosis is the increase in average production observed in crossbred females compared to straightbred females. Sci. Alternative Crossbreeding Systems Alternative crossbreeding systems use genetic differences among breeds, heterosis and complementarity, with differing degrees of effectiveness (Figure 5). 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. Crossbreeding is undertaken to: Utilise the desired attributes of two or more breeds Produce progeny better suited to target markets while maintaining environmental adaption CROSS BREEDING. AHDB Dairy - Commissioned by British dairy farmers, available here . 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. As an example, breed composition of Santa Gertrudis is ? Optimal sequence for bulls in a two-sire, three-breed rotation is shown in Table 5. One advantage is that heifers usually are initially mated to a bull of similar size as their own sire breed as part of the rotation. As in the two-breed rotation, the three breeds used should be complementary with maternal characteristics conducive to the breeding females role in a commercial herd. 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. National Beef Cattle Evaluation Consortium. - 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. General Considerations * Rotational systems generally make more effective use of heterosis. If Charolais bulls were mated to F1 Angus Hereford cows, calf weights would be predicted by adding individual and maternal heterosis to the average genetic merit of the crossbred calf. 4.39.3.1 Crossbreeding. Replacement females should be environmentally adapted with the necessary maternal capacities. GMO: Salmon that has been genetically engineered to get bigger is an example of GMO. Both tools offer the benefits of heterosis, breed differences and complementarity to help producers match genetic potential with market preferences, the climatic environment and available feed resources. Nature News, Nature Publishing Group, Available here . Brahman. Figure 3. Cattle breeders already have developed a significant number of composite populations in diverse geographic regions around the U.S. Terminal crossing. 51:1197. selection but heterosis generated through crossbreeding can significantly improve an animal's performance. In choosing a crossbreeding system, primary consideration must be given to a source of replacement females. What is the difference between Mesopotamia and Egypt? Which of the following is NOT considered an advantage of embryo transfer? J. Anim. What is the proper term for the measure of how inbred an animal is? In general, EPDs available for bulls from purebreds used in rotational systems tend to be more accurate than EPDs for bulls used in a composite population because they're based on a larger number of records. Individual and maternal heterosis for beef cattle. This has resulted from inbreeding accumulating in the breeds, because most were initiated from a relatively small genetic base. Santa Gertrudis and Brangus are examples, as are the MARC composites developed at the U.S. Meat Animal Research Center. One difficulty is that populations of purebred animals must be maintained to produce the crossbreds. Crossbred cattle at the University of Missouri South Farm Beef Research and Teaching Unit. Beef Sire Selection Manual. mating of related individuals in which the sire and dam share at least one ancestor. References to commercial products, trade names, or suppliers are made with the under- standing that no endorsement is implied and that no discrimination against other products or suppliers is intended. The two-breed rotation can be used with fewer cows; however, bull expenses per cow will be greater. Cost and availability of these resources need to be considered. * Composite populations maintain significant levels of heterosis, but less than rotational crossing of any specific number of contributing breeds. When crossed, the A B calves average 625 pounds at weaning. 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. Small herd size presents extra limitations on suitability of particular systems. 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). . When composites are used sires and dams do not differ, thus no breed complementation is offered. Definition: The deliberate breeding of two different individuals that results in offspring that carry part of the genetic material of each parent. Efficient crossbreeding systems for herds of this size would increase the productivity and profitability of the states beef industry. Accessed online at http://digitalcommons.unl.edu/ cgi/viewcontent.cgi?article=1235&context=rangebeefc owsymp on December 3, 2012. It is generally recommended to purchase bred heifers or cows so that the same herd sire(s) can be used for all breeding females. Our research shows that 50:50 Continental and British crosses perform well. Management is more complex than for the two-breed rotation. Genetically modified golden rice grains are shown in Figure 3. The rototerminal system is essentially a hybrid crossbreeding program using aspects of a terminal program and a rotational program. Modified static crossbreeding system. All progeny, both male and female, are produced for slaughter. Crossbreeding: One example is crossbreeding to increase milk production in cattle. Furthermore, management of breeding systems where multiple breeding pastures is required poses another obstacle. Normally, breeds are chosen that have complementary traits that will enhance the offsprings' economic value. Rotational systems have been popular in the pork industry. Before using this type of system, a producer needs to consider that no maternal heterosis will result from using straightbred females.

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