Genetic structure and inbreeding in Romney Marsh sheep in Brazil
DOI:
https://doi.org/10.5433/1679-0359.2023v44n1p437Keywords:
Ancestors, Average relatedness, Founders, Inbreeding, Pedigree information.Abstract
According to the last livestock census, Brazil has 17,976,367 head of sheep. Approximately 23.69% of this herd is located in the south region, where wool or wool and meat-producing breeds are predominately farmed. Inbreeding, or consanguinity, is defined as the mating of related individuals, which tends to occur when herds are small or originate from few parents. This study proposes to investigate the genetic structure and diversity of the Romney Marsh sheep herd in Brazil. The pedigree data used were obtained from the Brazilian Association of Sheep Breeders (ARCO), which keeps the sheep register database. For a more complete analysis, data from the Purebred Register Books were used. The population herein referred to as “total” comprised 22,833 individuals, whereas the population termed “reference” consisted of 17,053 records. Individual and average inbreeding coefficients, as well as overall frequencies, were calculated using SAS software. Demographic indicators were determined using ENDOG software. The average inbreeding coefficient found was 2.90% in the total population and 3.55% in the reference population. The minimum inbreeding value found in the studied population was 0.01% and the maximum was 43.47%. Inbred animals in the complete reference population were 10.31%. In 2018, inbred animals represented 82.55% of the registered population. The average generation interval was 4.0488 years. Due to the intensive use of few breeding lines and the high degree of genetic uniformity in the population, the Romney Marsh breed has narrow pedigree bottlenecks. The current population of the Romney Marsh breed has only two genetic origins, warranting the introduction of new genes to avoid genetic erosion and severe losses due to inbreeding.
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