Genetic diversity of Guernsey population using pedigree data and gene-dropping simulations

Abstract

The objectives of this study were to analyze the trend of within-breed genetic diversity and identify major causes leading to loss of genetic diversity in Guernsey breed in three countries. Pedigree files of Canadian (GCN), South African (GSA) and American (GUS) Guernsey populations containing 130 927, 18 593 and 1 851 624 records, respectively, were analyzed. Several parameters derived from the in-depth pedigree analyses were used to measure trends and current levels of genetic diversity. Pedigree completeness index of GCN, GSA and GUS populations, in the most recent year (2007), was 97%, 74% and 79%, respectively, considering four generations back in the analysis. The rate of inbreeding in each population was 0.19%, 0.16% and 0.17% between 2002 and 2007, respectively. For the same period, the estimated effective population size for GCN, GSA and GUS was 46, 57 and 46, respectively. The estimated percentage of genetic diversity lost within each population over the last four decades was 8%, 3% and 5%, respectively. The relative proportion of genetic diversity lost due to random genetic drift in the three populations was 93%, 91% and 86%, respectively. In conclusion, the results suggested that GCN and GUS have lost more genetic diversity than GSA over the past four decades, and this loss is gaining momentum due to increasing rates of inbreeding. Therefore, strategies such as optimum contribution selection and migration of genetic material are advised to increase effective population size, particularly in GCN and GUS.

Analysis of Endangered Andalusian Black Cattle (Negra Andaluza) Reveals Genetic Reservoir for Bovine Black Trunk

“…Genetic diversity loss (GDL) due to genetic bottlenecks and drift was relatively low (1.07), being nearly double the GDL due to unequal founder contributions (0.55), as observed in the Guernsey breed [39]. In contrast, other conservation breeds like Berrenda Negra and Colorada exhibited lower GDL values [54], indicating genetic bottlenecks and drift as primary causes of genetic diversity loss in the Andalusian Black cattle breed.…”

“…The Andalusian Black cattle breed exhibited a genetic diversity of 98.93% and a Genetic Conservation Index (total population) of 2.75, akin to other breeds under conservation programs such as Berrenda Negra and Berrenda Colorada in Spain [54]. However, the loss of genetic diversity was 1.07, which is relatively low compared to commercial dairy breeds experiencing losses between 3 and 11% [39].…”

“…While these values fall below the threshold of 0.6 for reliability in estimates, they have steadily improved since 2000, when the breed was included in the official catalog of Spanish bovine breeds, alongside enhanced management of genealogical records and genetic improvement plans by the association [2]. These values align with other bovine breeds undergoing conservation processes, such as the Curraleiro Pé Duro in Brazil, Italian Pontremolese, Sardo Modicana, and German Angler and Red and White dual-purpose breeds [36][37][38], but are lower than those in commercial-industrial dairy and beef cattle breeds with extensive record-keeping and genetic evaluation histories [39][40][41][42][43][44][45].…”