1,721,149 research outputs found
Using expected allele number as objective function to design between and within breed conservation of farm animal biodiversity
No full textConservation of genetic diversity in farm animal species can be achieved by preventing extinction of breeds and by reducing genetic drift within breeds. It is suggested to use the expected number of alleles segregating in the species after a given time period as objective function in the design of conservation strategies. A formal approach is presented to predict this quantity based on marker information, accounting for extinction probability of breeds and effective population size within breeds as the major component of genetic drift. Based on this model, relative efficiency of different strategies of diversity conservation can be quantified. Formulas are given to derive the marginal expected number of alleles with respect to genetic drift within population and extinction probability, respectively. The suggested approach is illustrated with an example of 13 European cattle breeds. With the assumed parameters, drift is shown to be the major force leading to loss of alleles, and different breeds are prioritized for activities to reduce risk of extinction and for measures to reduce genetic drift, respectively. Although different aspects of the model need to be further refined, the suggested methodology provides a general and flexible tool to derive the optimum conservation strategy in various scenarios
Decision making in livestock conservation
No full textIn this article, theory and practical implementations of decision making in livestock conservation are reviewed. It is argued that the objective of livestock conservation is a composite of maintaining between and within breed diversity and single breeds of recognised value. Assuming that this goal can be reflected in an objective function, decision making requires maximisation of this objective function with or without restrictions. Different strategies have been proposed in the literature to achieve this goal. While the diversity measure suggested by Weitzman (1992) [Weitzman, M.L., 1992. On diversity. Quart. J. Economics, CVII: 363-405.] is not fully appropriate to be applied to breed conservation within livestock species, the approach of maximising expected diversity Weitzman (1993) [Weitzman, M.L., 1993. What to preserve? An application of diversity theory to crane conservation. Quart. J. Economics, CVII: 157-183.] is seen as a fundamental concept in this area. Although highly elaborate methods of decision making are discussed in the scientific literature, the concepts presently used by national or international authorities or non-government organisations are rather simplistic, mainly risk-related and based on simple functions of population size. It is argued that decision making has to account for the global diversity of a species and therefore decisions and conservation activities should be coordinated on an international level. The use of more appropriate decision rules will strongly increase the cost efficiency of conservation investments. Livestock conservation should be based on an extended objective function reflecting the expected future value of the conserved set of breeds, which encompasses within and between breed diversity as well as specific traits and cultural or scientific value of the main breeds. A critical issue is the derivation of the required parameters like the breed value or the risk status of a breed. Since it will generally be difficult to obtain exact values, decision making under uncertainty will be the usual challenge and Bayesian decision theory might be an option. The optimum allocation pattern and implementation of conservation activities can be derived based on Weitzman's expected diversity concept. Approximate decision rules for breed prioritisation based on the extinction probability of a breed and its marginal objective function are given. Even if the respective parameters are not perfectly known, the use of the suggested approaches has the potential to double the cost efficiency, in terms of maintained diversity per conservation dollar spent, compared to the simplistic approaches that are used today. (c) 2005 Elsevier B.V. All rights reserved
Perspektiven der Tierzuchtwissenschaft
No full textAnimal breeding science is an applied science oriented towards the future. Regarding
the scientific content, perspectives are especially in the development of breeding
strategies to improve functional traits, in the implementation of novel molecular
genetic and biotechnological tools and findings, in the conservation of animal genet ic diversity, and in providing contributions to satisfy the globally increasing demand
for animal products. Classical quantitative-genetic based and novel molecular based
approaches are fully complementary. To increase the economic efficiency of animal
production through breeding is an essential prerequisite for an internationally com petitive German animal breeding industry. Regarding the structural and organisa tional perspectives, it will be necessary to develop co-operations between scientific
groups with complementary profile in the future. Animal breeding science is split in
basic research aiming at a better understanding of underlying processes, applied
research focusing on solving practical problems, and between the two transfer-ori ented research trying to make results of basic research applicable in practical animal
breeding. In general, scientists and practical animal breeders need to strengthen the
exchange and to develop a better understanding of the needs and obligations of the
other partner, respectively. Here, the German Society for Animal Production will con tinue to play a major role as a mediator between science and practice.Die Tierzuchtwissenschaft ist eine anwendungsorientierte, zukunftsorientierte Wissenschaft. Inhaltliche Perspektiven bestehen insbesondere in der Weiterentwicklung züchterischer Ansätze zur Verbesserung funktionaler Merkmale, der Einbindung neuer molekulargenetischer und biotechnologischer Methoden und Erkenntnisse in den Züchtungsprozess, der Erhaltung der genetischen Diversität der Nutztiere und der Entwicklung züchterischer Beiträge zur Befriedigung der weltweit steigenden Nachfrage nach Lebensmitteln tierischen Ursprungs. Klassische quantitativ-genetische Tierzucht und neuere molekularbiologische Ansätze ergänzen sich hier gegenseitig. Die züchterische Steigerung der ökonomischen Effizienz der Nutztiere ist eine zentrale Voraussetzung für den Bestand einer international konkurrenzfähigen deutschen Tierzucht. Neben den inhaltlichen Perspektiven werden auch die strukturellen Perspektiven der Tierzuchtforschung diskutiert. Hier zwingt die Entwicklung der Rahmenbedingungen dazu, regionale Verbünde komplementär ausgerichteter Forschungsgruppen zu entwickeln, welche im Rahmen einer gemeinsamen inhaltlichen Zielsetzung international konkurrenzfähige Forschung betreiben können. Neben der Grundlagenforschung und der Problemlösungsforschung kommt in der Tierzucht der Transferforschung eine große Bedeutung zu, welche das Ziel hat, Ergebnisse der Grundlagenforschung der Praxis verfügbar zu machen. Generell sind Wissenschaftler wie Praktiker gefordert, den Austausch zu suchen und für die Erfordernisse und Zwänge der jeweils anderen Seite Verständnis zu entwickeln. Hierbei kann die Deutsche Gesellschaft für Züchtungskunde als Mittler zwischen Wissenschaft und Praxis weiterhin eine wichtige Rolle spielen
Ist Zucht auf Krankheitsresistenz erfolgreich?
No full textAnimal health is important both from the perspective of animal welfare and food quality. Also, healthy animals are a prerequisite for economically successful animal production. Health problems can be classified in infectious diseases, genetic disorders and functional diseases. In each case, different approaches are required for genetic improvement. Breeding for disease resistance is not trivial, due to the low heritability of the respective traits, unfavourable genetic correlations to important production traits, and problems to organise a population-wide recording system efficiently. Experimental studies have shown, that breeding for immune capacity based on quantitative immunological parameters is possible. Traditionally, the Scandinavian countries run efficient recording schemes for health traits and give those traits a high weight in their breeding goals. For mastitis in dairy cattle it is shown, that these activities result in a positive genetic trend for this trait relative to the trend in Germany. Marker-assisted selection against genetic defects in pigs is shown to be potentially very efficient. Compared to selection based on frequencies of defects in a boar's progeny, a marker-based pre selection of young boars is shown to lead to a significant increase in genetic progress. In conclusion, the type of recorded health traits, quality of recording and the relative weight of health traits in the breeding goal are seen as the most critical factors affecting efficiency of selection. New technologies and selection strategies have the potential to speed up the genetic trend towards more healthy animals
Approaches to the management of inbreeding and relationship in the German Holstein dairy cattle population
No full textThe aim of this study was to estimate the current level of inbreeding in the German cow population and for bull dams born in Germany, to find out sires most related to different subsets of their breed and to demonstrate the negative effect of homozygosity in the case of complex vertebral malformation (CVM). Further on, the application of optimum genetic contribution (OGC) theory for the selection of bull dams and bull sires in different breeding scenarios was investigated. Levels of inbreeding for the cow population were in a low range from 0.97% to 1.70% evaluating birth years from 1996 to 1999 in a total dataset of 244,427 registered Holstein cows. The inbreeding coefficient of 8030 bull dams was much higher, i.e. 3.71%, for the birth year 1999. Increases in inbreeding of 0.19% per year indicated an effective population size of only 52 animals. Individual sires like R.O.R.A. Elevation and Hannoverhill Starbuck were highly related to potential bull dams with coefficients of relationship of 13.4% and 12.9%, respectively, whereas RE Arlinda Chief (16.3%) and Carlin-M Ivanhoe Bell (16.1%) were highest related to the best available AI sires. Coefficients of relationship were calculated by classes of estimated breeding values (EBV) for production traits showing highest values above 7% in the two highest EBV-classes. The optimum genetic contribution theory using official EBVs and approximative, for zero inbreeding corrected EBVs, was applied for elite matings in a breeding program embracing 30 young bulls per year to find the optimal allocations of bull sires and bull dams. Compared with the actual breeding program applied in practice, OGC-theory has the potential to increase genetic gain under the same constraint for the increase of average relationship by 13.1 %. A more relaxed constraint on increase in inbreeding allowed even higher expected genetic gain whereas a more severe constraint resulted in more equal contributions of selected bull sires. Contributions from 21 selected bull sires and 30 selected bull dams for a scenario at 5% constrained relationship were used to develop a specific mating plan to minimise inbreeding in the short term in the following generation applying a simulated annealing algorithm. The expected coefficient of inbreeding of progeny was 66.3% less then the one resulting from random mating. Mating programs can address inbreeding concerns on the farm, at least in the short term, but long-term control of inbreeding in a dairy population requires consideration of relationships between young bulls entering AI progeny test programs. Significantly better EBVs of CVM-free bulls compared with CVM-carriers for the paternal fertility justify the application of OGC for elite matings. (c) 2006 Elsevier B.V. All rights reserved
Genomic selection – basics and perspectives for dairy cattle breeding programs
No full textIn der Milchrinderzucht hat die markergestützte Selektion die in sie gesetzten hohen Erwartungen bislang kaum erfüllen können. Der Zuchtfortschritt beruht nach wie vor auf den klassischen Methoden der Zuchtwertschätzung auf der Basis von Leistungsprü-fungsdaten, welche insbesondere beim Milchrind lange Generationsintervalle implizieren. Der Ansatz der „genombasierten Selektion“ könnte sowohl die Methoden der Zuchtwertschätzung revolutionieren, als auch zu ganz neuen Strukturen von Zuchtprogrammen führen. Genombasierte Selektionsverfahren sind möglich auf Grund der Verfügbarkeit so genannter SNP. Diese sind im Genom sehr häufig und können kostengünstig in großer Zahl auf so genannten SNP-Chips typisiert werden. Der genomische Zuchtwert eines Tieres ist dann die Summe der einzelnen SNP-Effekte und ist somit sofort verfügbar, wenn das Tier seine genetische Identität erlangt hat, also z.B. sogar schon für Embryonen. Das bedeutet auch eine Abkehr von der bisherigen Pedigree-basierten Zuchtwertschätzung (BLUP-Tiermodell) hin zu einem SNP-basierten BLUP-Ansatz, wobei Verwandteninformationen eine viel geringere Rolle spielen. Der wesentliche Faktor ist, dass schon bei jungen Tieren beiderlei Geschlechts eine Genauigkeit der Zuchtwertschätzung von 0,75 erreicht wird. In Rinderzuchtprogrammen besteht die größte Effizienzreserve in der Verkürzung des Generationsintervalls auf der Bullenseite durch Verzicht auf die Nachkommenprüfung. Modellrechnungen auf Basis der Struktur des kanadischen Holsteinzuchtprogramms kamen zu dem Ergebnis, dass eine konsequente Umsetzung der genombasierten Selektion zu einer Verdoppelung des Zuchtfortschritts pro Jahr bei einer Reduzierung der Züchtungskosten um 90 Prozent führen kann. Abschließend werden offene Fragen der Methodik und der Umsetzung diskutiert.Practical improvements of dairy cattle breeding programs through marker assisted selection were behind theoretical expectations. Genetic gain is still based on traditional recording systems and progeny testing programs, but the theoretical potential is limited due to long generation intervals. Genomic selection enables the opportunity for substantial modifications of genetic evaluations and breeding programs as well. Genomic selection is possible due to a multitude of so called SNPs, distributed more or less evenly over the whole genome, and costs for SNP-genotyping through microarray technology are relatively cheap compared to microsatellite markers. The genomic breeding value is the sum of all single SNP effects. Reliable genomic breeding values for both sexes (accuracy > 0.75) can be calculated in an early stage of an animal’s life, e.g. even for embryos. This implies a shift from BLUP animal models including pedigree information towards SNP based BLUP, and putting less weight on information provided by relatives. Economic efficiency and an increase of selection response in dairy cattle breeding programs are due to the entire abdication of progeny testing. Such a strategy implies a substantial reduction in generation intervals. Model calculations for the Canadian Holstein population showed a doubling of selection response per year and a reduction of breeding costs by 90 percent when comparing genomic selection to the traditional selection scheme. However, unresolved problems related to the methodology for the estimation of SNP-effects have to be clarified in advance
Ist Zucht auf Krankheitsresistenz erfolgreich?
No full textAnimal health is important both from the perspective of animal welfare and food quality. Also, healthy animals are a prerequisite for economically successful animal production. Health problems can be classified in infectious diseases, genetic disorders and functional diseases. In each case, different approaches are required for genetic improvement. Breeding for disease resistance is not trivial, due to the low heritability of the respective traits, unfavourable genetic correlations to important production traits, and problems to organise a population-wide recording system efficiently. Experimental studies have shown, that breeding for immune capacity based on quantitative immunological parameters is possible. Traditionally, the Scandinavian countries run efficient recording schemes for health traits and give those traits a high weight in their breeding goals. For mastitis in dairy cattle it is shown, that these activities result in a positive genetic trend for this trait relative to the trend in Germany. Marker-assisted selection against genetic defects in pigs is shown to be potentially very efficient. Compared to selection based on frequencies of defects in a boar's progeny, a marker-based pre selection of young boars is shown to lead to a significant increase in genetic progress. In conclusion, the type of recorded health traits, quality of recording and the relative weight of health traits in the breeding goal are seen as the most critical factors affecting efficiency of selection. New technologies and selection strategies have the potential to speed up the genetic trend towards more healthy animals
Past and future activities to harmonize farm animal biodiversity studies on a global scale
No full textEconomic evaluation of genomic breeding programs
No full textThe objective of this study was to compare a conventional dairy cattle breeding program characterized by a progeny testing scheme with different scenarios of genomic breeding programs. The ultimate economic evaluation criterion was discounted profit reflecting discounted returns minus discounted costs per cow in a balanced breeding goal of production and functionality. A deterministic approach mainly based on the gene flow method and selection index calculations was used to model a conventional progeny testing program and different scenarios of genomic breeding programs. As a novel idea, the modeling of the genomic breeding program accounted for the proportion of farmers waiting for daughter records of genotyped young bulls before using them for artificial insemination. Technical and biological coefficients for modeling were chosen to correspond to a German breeding organization. The conventional breeding program for 50 test bulls per year within a population of 100,000 cows served as a base scenario. Scenarios of genomic breeding programs considered the variation of costs for genotyping, selection intensity of cow sires, proportion of farmers waiting for daughter records of genotyped young bulls, and different accuracies of genomic indices for bulls and cows. Given that the accuracies of genomic indices are greater than 0.70, a distinct economic advantage was found for all scenarios of genomic breeding programs up to factor 2.59, mainly due to the reduction in generation intervals. Costs for genotyping were negligible when focusing on a population-wide perspective and considering additional costs for herdbook registration, milk recording, or keeping of bulls, especially if there is no need for yearly recalculation of effects of single nucleotide polymorphisms. Genomic breeding programs generated a higher discounted profit than a conventional progeny testing program for all scenarios where at least 20% of the inseminations were done by genotyped young bulls without daughter records. Evaluation of levels of annual genetic gain for individual traits revealed the same potential for low heritable traits (h(2) = 0.05) compared with moderate heritable traits (h(2) = 0.30), preconditioning highly accurate genomic indices of 0.90. The final economic success of genomic breeding programs strongly depends on the complete abdication of any forms of progeny testing to reduce costs and generation intervals, but such a strategy implies the willingness of the participating milk producers
Application of controlling instruments for improvements in cow sire selection
No full textNational estimated breeding values of bulls from 1998 through 2006 from 12 different German artificial insemination (AI) organizations were used to determine the differences in expected and realized selection intensities for cow sire selection, considering the total merit index as well as subindexes for production, conformation, somatic cell count, fertility, and functional herd life. The expected selection intensity was derived from a Gaussian distribution and from the replacement rate describing the percentage of bulls graduated as cow sires from the total amount of progeny-tested young bulls within the AI organization and by birth year. Realized selection intensities for all indexes were derived from the selection differential of cow sires, defined as the deviation of the average index of selected cow sires from the average index of the total number of progeny-tested young bulls. A low replacement rate of cow sires was associated with relatively high realized selection intensities for the total merit, production, and conformation indexes, but was not related to the somatic cell count, fertility, and functional herd life indexes. The controlling value, defined as the ratio of realized to expected selection intensities, indicates the effectiveness of cow sire selection for different traits. Low controlling values (i.e., low realized selection intensities in combination with moderate or high expected selection intensities) suggest improvements in the step of cow sire selection, especially when discussing the total merit index. Analysis of variance revealed significant differences in expected selection intensities, realized selection intensities, and controlling values for the total merit, production, and conformation indexes between AI organizations and birth years of bulls. Artificial insemination organizations applying well-defined breeding policies (e.g., high controlling values for the total merit index) were successful in the national competition when evaluated according to the national top lists for the respective indexes, regardless of the active population size. The suggested method also allows for comparison of the importance of different indexes in selection decisions. Furthermore, controlling values can monitor additional potential in the improvement of cow sire selection with respect to improvement of the genetic level in the whole population. The development of appropriate selection tools or controlling instruments is of increasing concern for monitoring selection policies in the short term as well as for establishing sustainable breeding policies
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