Abstract
BackgroundAssessment of genetic diversity and population structure provides important control metrics to avoid genetic erosion, inbreeding depression and crossbreeding between exotic and locally-adapted cattle breeds since these events can have deleterious consequences and eventually lead to extinction. Historically, the Alpine Arc represents an important pocket of cattle biodiversity with a large number of autochthonous breeds that provide a fundamental source of income for the entire regional economy. By using genotype data from medium-density single nucleotide polymorphism (SNP) arrays, we performed a genome-wide comparative study of 23 cattle populations from the Alpine Arc and three cosmopolitan breeds.ResultsAfter filtering, we obtained a final genotyping dataset consisting of 30,176 SNPs for 711 individuals. The local breeds showed high or intermediate values of genetic diversity compared to the highly selected cosmopolitan breeds. Patterns of genetic differentiation, multidimensional scaling, admixture analysis and the constructed phylogenetic tree showed convergence, which indicates the presence of gene flow among the breeds according to both geographic origin and historical background. Among the most differentiated breeds, we identified the modern Brown cattle. In spite of admixture events, several local breeds have preserved distinctive characteristics, which is probably due to differences in genetic origin and geographic location.ConclusionsThis study represents one of the most comprehensive genome-wide analysis of the Alpine cattle breeds to date. Using such a large dataset that includes the majority of the local breeds found in this region, allowed us to expand knowledge on the evaluation and status of Alpine cattle biodiversity. Our results indicate that although many of the analyzed local breeds are listed as endangered, they still harbor a large amount of genetic diversity, even when compared to some cosmopolitan breeds. This finding, together with the reconstruction of the phylogeny and the relationships between these Alpine Arc cattle breeds, provide crucial insights not only into the improvement of genetic stocks but also into the implementation of future conservation strategies.
Highlights
Assessment of genetic diversity and population structure provides important control metrics to avoid genetic erosion, inbreeding depression and crossbreeding between exotic and locally-adapted cattle breeds since these events can have deleterious consequences and eventually lead to extinction
In addition to the indigenous breeds from the Alpine region, we analyzed three cosmopolitan breeds: two were used as outgroups, i.e. Italian Holstein (HOLS) that originated from the Netherlands and is currently a cosmopolitan dairy breed, and Jersey (JERS), a dairy breed native from Jersey island but currently defined as cosmopolitan; and one breed was included because of its historical relationships with local Alpine breeds, i.e. Brown Swiss, which is represented by three populations because it derives from a genetic stock of original Brown, it was imported to the USA, strongly selected for milk production and subsequently reintroduced to worldwide countries including Italy (BRIT), Germany (BRDE) and Switzerland (BRSW)
Genetic diversity indices for the 28 populations analyzed are in Table 1. Ho ranged from 0.297 ± 0.198 to 0.356 ± 0.163 and He ranged from 0.286 ± 0.176 to 0.347 ± 0.141; both minimum and maximum values for Ho and He were obtained for the Jersey and Cika breeds, respectively
Summary
Assessment of genetic diversity and population structure provides important control metrics to avoid genetic erosion, inbreeding depression and crossbreeding between exotic and locally-adapted cattle breeds since these events can have deleterious consequences and eventually lead to extinction. The Alpine Arc represents an important pocket of cattle biodiversity with a large number of autochthonous breeds that provide a fundamental source of income for the entire regional economy. Unplanned genetic introgression and crossbreeding have largely contributed to the loss of indigenous breeds. Within this context, increasing the knowledge on the genomic architecture of these breeds is crucial for both maintaining and improving proper selection strategies. Actions that take the ever-changing environmental conditions and market demands into account are becoming increasingly essential
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