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We have evaluated the use of genomic coancestry coefficients based on shared segments for the maintenance of genetic diversity through optimal contributions methodology for populations of three different Austrian cattle breeds. This coancestry measure has been compared with the genomic coancestry coefficient calculated on a SNP-by- SNP basis and with pedigree-based coancestry. The regressions of the shared segments coancestry on the other two coefficients suggest that the former mainly reflect Identity By Descent but with the advantage over pedigree-based coancestry of providing the realized Identity By Descent rather than an expectation. The effective population size estimated from the rate of coancestry based on shared segments was very similar to those obtained with the other coefficients and of small magnitude (from 26.24 to 111.90). This result highlights the importance of implementing active management strategies to control the increase of inbreeding and the loss of genetic diversity in livestock breeds, even when the population size is reasonably large. One problem for the implementation of coancestry based on shared segments is the need of estimating the gametic phases of the SNPs which, given the techniques used to obtain the genotypes, are a priori unknown. This study shows, through computer simulations, that using estimates of gametic phases for computing coancestry based on shared segments does not lead to a significant loss in the diversity maintained. This has been shown to be true even when the size of the population is very small as it is usually the case in populations subjected to conservation programmes. [ABSTRACT FROM AUTHOR]

Abstract: Sperm cryobanking could be a good alternative to breeding in captivity in order to preserve genetic diversity. Sperm from two well-characterized brown trout populations originating from two river basins in the Northwest of Spain (Esla and Duerna), both threatened by extinction, was cryopreserved. In order to determine whether a sperm cryobank is the best option for preserving genetic profiles, cell viability, chromatin fragmentation, fertility and genetic variability of the offspring obtained with fresh and frozen sperm, were analyzed. Sperm viability was not reduced by freezing (87.0±3.32% to 77.9±3.59% and 77.6±6.53% to 76.6±2.61% in fresh and frozen sperm from Esla and Duerna, respectively). The percentage of fragmented DNA increased after freezing in spermatozoa from Esla males (from 4.7±0.23% to 6.0±0.28%), but not those from Duerna males. After freezing/thawing, the percentage of eyed embryos drops from 66.8±6.77% to 16.1±3.46% and from 50±8.97% to 11.5±2.50% in the Esla and Duerna basins, respectively. This reduction indicates that many spermatozoa have lost their ability to contribute to embryo development and this loss is not related to either spermatozoa viability or the DNA integrity. Genotypic determination by microsatellite analysis showed that frozen/thawed sperm provided offspring with a similar genetic profile to unfrozen milt, demonstrating the accuracy of the cryopreservation procedure. Taking into account the prolificacy of this species, even a low rate of success of fry after cryopreservation, could provide enough individuals to recover stable populations without altering the genetic profiles of the preserved strains. Therefore, cryopreservation is considered a safe, simple and cheap technology for gene banking in the analyzed brown trout populations. [Copyright &y& Elsevier]