Buzz: Face-to-Face Contact and the Urban Economy

This paper argues that existing models of urban concentrations are incomplete unless grounded in the most fundamental aspect of proximity; face-to-face contact. Face-to-face contact has four main features; it is an efficient communication technology; it can help solve incentive problems; it can facilitate socialization and learning; and it provides psychological motivation. We discuss each of these features in turn, and develop formal economic models of two of them. Face-to-face is particularly important in environments where information is imperfect, rapidly changing, and not easily codified, key features of many creative activities.Agglomeration, clustering, urban economics, face-to-face

Impact of the use of cryobank samples in a selected cattle breed: a simulation study

<p>Abstract</p> <p>Background</p> <p>High selection pressure on domestic cattle has led to an undesirable increase in inbreeding, as well as to the deterioration of some functional traits which are indirectly selected. Semen stored in a cryobank may be a useful way to redirect selection or limit the loss of genetic diversity in a selected breed. The purpose of this study was to analyse the efficiency of current cryobank sampling methods, by investigating the benefits of using cryopreserved semen in a selection scheme several generations after the semen was collected.</p> <p>Methods</p> <p>The theoretical impact of using cryopreserved semen in a selection scheme of a dairy cattle breed was investigated by simulating various scenarios involving two negatively correlated traits and a change in genetic variability of the breed.</p> <p>Results</p> <p>Our results indicate that using cryopreserved semen to redirect selection will have an impact on negatively selected traits only if it is combined with major changes in selection objectives or practices. If the purpose is to increase genetic diversity in the breed, it can be a viable option.</p> <p>Conclusions</p> <p>Using cryopreserved semen to redirect selection or to improve genetic diversity should be carried out with caution, by considering the pros and cons of prospective changes in genetic diversity and the value of the selected traits. However, the use of genomic information should lead to more interesting perspectives to choose which animals to store in a cryobank and to increase the value of cryobank collections for selected breeds.</p

The impact of genomic selection on genetic diversity and genetic gain in three French dairy cattle breeds

International audienceAbstractBackgroundIn France, implementation of genomic evaluations in dairy cattle breeds started in 2009 and this has modified the breeding schemes drastically. In this context, the goal of our study was to understand the impact of genomic selection on the genetic diversity of bulls from three French dairy cattle breeds born between 2005 and 2015 (Montbéliarde, Normande and Holstein) and the factors that are involved.MethodsWe compared annual genetic gains, inbreeding rates based on runs of homozygosity (ROH) and pedigree data, and mean ROH length within breeds, before and after the implementation of genomic selection.ResultsGenomic selection induced an increase in mean annual genetic gains of 50, 71 and 33% for Montbéliarde, Normande and Holstein bulls, respectively, and in parallel, the generation intervals were reduced by a factor of 1.7, 1.9 and 2, respectively. We found no significant change in inbreeding rate for the two national breeds, Montbéliarde and Normande, and a significant increase in inbreeding rate for the Holstein international breed, which is now as high as 0.55% per year based on ROH and 0.49% per year based on pedigree data (equivalent to a rate of 1.36 and 1.39% per generation, respectively). The mean ROH length was longer for bulls from the Holstein breed than for those from the other two breeds.ConclusionsWith the implementation of genomic selection, the annual genetic gain increased for bulls from the three major French dairy cattle breeds. At the same time, the annual loss of genetic diversity increased for Holstein bulls, possibly because of the massive use of a few elite bulls in this breed, but not for Montbéliarde and Normande bulls. The increase in mean ROH length in Holstein may reflect the occurrence of recent inbreeding. New strategies in breeding schemes, such as female donor stations and embryo transfer, and recent implementation of genomic evaluations in small regional breeds should be studied carefully in order to ensure the sustainability of breeding schemes in the future

Genetic diversity of a large set of horse breeds raised in France assessed by microsatellite polymorphism

After the recent publication of our article (Leroy, Genetics Selection Evolution 2009 41:5), we found several errors in the published Table Three, concerning the computation of contribution to within-breed diversity (CW). We apologize to the readers for these errors, which are corrected in the present erratum

Innovations in cryoconservation of animal genetic resources. Practical guide

Peer reviewe

For a sustainable management of the genetic variability of livestock populations by combining in situ and ex situ strategies

En France, la conservation et la gestion de la variabilité génétique des populations de ruminants est un champ important de recherche et d'activité. L'expérience française combine des actions de terrain efficaces ; la préservation des populations ex situ grâce à la Cryobanque nationale ; des recherches méthodologiques débouchant sur des recommandations pratiques ; le développement d'indicateurs de la variabilité génétique des populations et de logiciels correspondants. Cette étude propose d'élaborer un bilan des actions de gestion et conservation de la variabilité génétique réalisées in situ via le calcul d'indicateurs, et l'évaluation des collections de la Cryobanque nationale à partir de différents critères.A partir de bilans de variabilité génétique, réalisés à partir des généalogies de 69 populations de ruminants sélectionnés en France, quatre facteurs majeurs expliquent la variation des valeurs des indicateurs de variabilité. Ce sont : le taux de pénétration de l'IA ; l'effectif des reproducteurs ; les systèmes de gestion de la diversité ; l'existence ou non d'introgression de gènes étrangers. Ces facteurs varient fortement suivant les filières considérées : bovins laitiers, petits ruminants laitiers, bovins allaitants, ovins allaitants et races à petits effectifs.Une évaluation des dispositifs d'échantillonnage de la Cryobanque montre, pour les bovins laitiers, l'efficacité du dispositif, mais qu'il pourrait être amélioré en échantillonnant les candidats à la Cryobanque principalement pour les caractères les moins sélectionnés. Pour les races allaitantes, le bilan est plus mitigé. Les candidats aux collections sont limités aux mâles prélevés en centre d'IA or ils restent une minorité des reproducteurs. Quant à la réintroduction de matériel cryoconservé dans des populations fortement sélectionnées, une simulation montre qu'elle ne peut être efficace qu'accompagnée d'un changement des objectifs de sélection. Pour les races menacées ou faiblement sélectionnées, la conservation de gènes ex situ pour préserver la variabilité génétique s'avère en revanche très efficace.Les travaux réalisés permettent de mieux utiliser les indicateurs de variabilité génétique. Une suite à cette étude est le projet VARUME. Il est proposé d'automatiser la mise à jour de ces indicateurs de variabilité génétique pour toutes les populations de ruminants avec des pedigrees. Pour la Cryobanque, une meilleure valorisation et optimisation des collections est envisagée à travers différents projets, dont VARUME et CRB-Anim.In France, the preservation and the management of the genetic variability of ruminants' breeds is an important field of research and activity. The French experience combines effective field actions; ex situ conservation thanks to the French national Cryobank; methodological researches resulting in practical recommendations; development of genetic variability indicators and corresponding software. This study is an assessment of the in situ actions of conservation and management of genetic variability via the estimation of indicators, and an evaluation of the collections of the national Cryobanque with various criteria.Thanks to an assessment of the genetic variability based on the pedigrees of 69 ruminants breeds selected in France, we found four major factors explaining variation of the values of the indicators of genetic variability. They are: the rate of IA; the number of reproducing females; the genetic variability management systems; the existence of the introgression of foreign genes. These factors vary strongly depend on the industry considered: dairy cattle, dairy small ruminants, beef cattle, sheep and rare breeds.An evaluation of the Cryobank sampling strategies shows that, for dairy cattle, the sampling is efficient, but it could be improved by selecting the Cryobank candidates mostly on the least selected traits. For meat breeds, the sampling is less successful. The Cryobank candidates are restricted to AI males, which remain a minority of the breeding males. As for the reintroduction of cryoconserved material in selected populations, a simulation shows that it is effective only if carried on with a change in the selection objectives. For rare or less selected breeds, ex situ conservation turn out to be effective to preserve the breeds' genetic variability.Genetic variability indicators can be used more appropriately, thanks to our study. A follow up will be the VARUME project. The main goal of this project is to automate the genetic variability indicators, for all ruminant breeds with pedigrees. As for the French Cryobank, various projects, including VARUME and CRB-Anim, will allow a better valuation and optimization of its collections