1,721,476 research outputs found
Genomic selection - basics and perspectives for dairy cattle breeding programs
No full textPractical 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
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
A model calculation on the prospects of an improvement of claw health in dairy cattle via genetic selection
No full textInvoluntary cullings due to feet and leg disorders are of increasing concern and reach nearly the same magnitude as those caused by fertility problems or mastitis. Conventionally, breeding programs only indirectly include a selection for improved claw health when using estimated breeding values from four different conformation traits. The direct selection path against the disorder, i.e. laminitis, seems to be more powerful to substantially improve the health status of the population. The aim of the present study was to quantify the relative importance of different index traits with respect to the selection response for the trait laminitis resistance. Index sources for estimated breeding values of bulls were laminitis observations and linear scores for hock quality of daughters and one claw measure (hardness of the dorsal wall) of the bull combined in different scenarios. The application of a selection index requires the availability of appropriate genetic parameters. The heritability estimate using logistic models for laminitis was 0.14. Genetic correlations between laminitis and conformation traits of feet and legs were, apart from those for heel depth, favourable with respect to the breeding objective. Phenotypic and genetic correlations between laminitis and claw measures of young bulls and between conformation traits scored for daughters and claw measures were near zero. Solely the claw hardness measure of young bulls seemed to be an appropriate indicator for the incidence of laminitis of daughters. Selection response in laminitis resistance per generation and accuracy of estimated breeding values of bulls could be doubled when laminitis observations of 50 daughters were included as index traits. To be effective in selection, breeding designs enabling the routine recording of claw disorders should be developed. The necessity of scoring conformation traits describing the feet and legs and the measurements of claws of young bulls is questionable with respect to the improvement of laminitis resistance and should carefully be evaluated
A model calculation on the prospects of an improvement of claw health in dairy cattle via genetic selection
No full textInvoluntary cullings due to feet and leg disorders are of increasing concern and reach nearly the same magnitude as those caused by fertility problems or mastitis. Conventionally, breeding programs only indirectly include a selection for improved claw health when using estimated breeding values from four different conformation traits. The direct selection path against the disorder, i.e. laminitis, seems to be more powerful to substantially improve the health status of the population. The aim of the present study was to quantify the relative importance of different index traits with respect to the selection response for the trait laminitis resistance. Index sources for estimated breeding values of bulls were laminitis observations and linear scores for hock quality of daughters and one claw measure (hardness of the dorsal wall) of the bull combined in different scenarios. The application of a selection index requires the availability of appropriate genetic parameters. The heritability estimate using logistic models for laminitis was 0.14. Genetic correlations between laminitis and conformation traits of feet and legs were, apart from those for heel depth, favourable with respect to the breeding objective. Phenotypic and genetic correlations between laminitis and claw measures of young bulls and between conformation traits scored for daughters and claw measures were near zero. Solely the claw hardness measure of young bulls seemed to be an appropriate indicator for the incidence of laminitis of daughters. Selection response in laminitis resistance per generation and accuracy of estimated breeding values of bulls could be doubled when laminitis observations of 50 daughters were included as index traits. To be effective in selection, breeding designs enabling the routine recording of claw disorders should be developed. The necessity of scoring conformation traits describing the feet and legs and the measurements of claws of young bulls is questionable with respect to the improvement of laminitis resistance and should carefully be evaluated
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Influence of milk production traits and genetic effects on milking frequency in an automatic milking system
No full textData from 10 different farms located in the region of Northwest Germany were used to investigate the impact of milk production traits on milking frequencies in automatic milking systems. Further on, genetic parameters for the behavioural trait 'milking frequency per cow and day' were estimated applying different statistical models. The analysis was done based on a generally stratification of cows in different classes for days in milk. The development of the milking frequency over lactation is characterised by a small decrease from the first (0 - 99 days in milk) to the second (100 - 199 days in milk) days in milk class, but a substantial decrease from the second to the third (200 - 299 days in milk) interval. Additionally, cows in first lactation have a higher milking frequency than older cows mainly due to higher activity and curiosity. The correlations between milk fat, milk protein and somatic cell score were slightly negative but near zero. An increase of these components causes a decrease of the milking frequency. The combination of milk protein content and milk urea content reflects the nutritional condition of the cows. Cows characterized by a surplus of energy tend to have fewer visits in the automatic milking system compared with cows having a balanced or even negative status of energy. The genetic impact revealed moderate heritabilities for the number of milkings per day in the range from 0.26 to 0.42 for the different days in milk classes and applied models. In the second half of the lactation heritabilities were slightly higher due to fewer disturbing environmental effects like fetching the cows towards the milking box. In conclusion, heritabilities for milking frequency in automatic milking systems are sufficient to incorporate this behavioural trait in a combined breeding goal for dairy cattle
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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