Molecular and pedigree analysis applied to conservation of animal genetic resources: the case of Brazilian Somali hair sheep

Abstract

The first registers of Somali sheep in Brazil are from the beginning of the 1900s. This breed, adapted to the dry climate and scarce food supply, is restricted in the northeast region of the country. Molecular marker technologies, especially those based on genotyping microsatellite and mtDNA loci, can be used in conjunction with breeding (pedigree analysis) and consequently the maintenance of genetic variation in herds. Animals from the Brazilian Somali Conservation Nuclei from Embrapa Sheep and Goats in Ceará State were used to validate genetic monitoring by traditional pedigree methods and molecular markers. Nineteen microsatellite markers and 404 base pairs from the control region of mtDNA were used. For total herd diversity, an average 5.32 alleles were found, with expected heterozygosity of 0.5896, observed heterozygosity of 0.6451, 0.4126 for molecular coancestrality, and coefficient of inbreeding (F (IS)) was -0.095. Comparing molecular coancestrality means over the years, there was a consistent increase in this parameter within the herd, increasing from 0.4157 to 0.4769 in 2 years (approx. 12% variation). Sixteen mtDNA haplotypes were identified. Inbreeding and other estimates from genealogical analyses confirm the results from molecular markers. From these results, it is possible to state that microsatellites are useful tools in genetic management of herds, especially when routine herd recording is not carried out, or there were gaps in recent generations. As well as pedigree control, genetic diversity can be optimized. Based on the results, and despite herd recording in the herd of Brazilian Somali of Embrapa Sheep and Goats, additional management measures need to be carried out in this herd to reduce inbreeding and optimize genetic variation.

Parâmetros populacionais da raça ovina Santa Inês no Brasil

“…Em 1991, ocorreu aumento expressivo e abrupto, com valor máximo de 12,22%, e, no período de 1992 a 2010, o F apresentou relativa estabilização, com média de 7,49%. Se admitirmos que valor de F superior a 10% representa risco elevado para ocorrência de depressão por endogamia (Paiva et al, 2011), a raça Santa Inês, com exceção do ano de 1991, apresentou médias anuais dentro de limites satisfatórios. A ausência de endogamia verificada nos primeiros sete anos de formação da raça não foi resultante da inexistência de animais endogâmicos na população, mas sim do número reduzido de ancestrais conhecidos até então, o que impossibilitou a determinação desse parâmetro.…”

“…O estudo da estrutura populacional baseado em informações de pedigree, embora apresente algumas desvantagens, como a baixa integridade ou imprecisão dos dados para animais de produção (Ron et al, 1996), tem sido realizado em diferentes populações ovinas de diversas partes do mundo (Maiwashe & Blackburn, 2004;Goyache et al, 2010;Paiva et al, 2011;Ghafouri-Kesbi, 2012).…”

Genetic diversity of locally adapted sheep from Pantanal region of Mato Grosso do Sul

“…This result may be due to the small sample population (15 individuals), and due to the population being consolidated with planned genetic crosses established from breeding programs. Several studies using locally adapted or native breeds confirmed that these breeds have more number of loci in HWE when compared to more specialized breeds (McManus et al, 2010;Paiva et al, 2011a;Tolone et al, 2012).…”

Naturalized Breeds in Brazil: Reports on the Origin and Genetic Diversity of the Pantaneiro Sheep

“…Knowledge of the population structure combined with information about genetic changes can influence future management actions and can be used to develop strategies for using a breed in a particular ecosystem as a model for genetic improvement programs [41]. Conservation programs using molecular tools are crucial for the providing information about the genetic diversity of locally adapted groups, thus allowing them to be included in production systems for integration of adaptation and rusticity features [12].…”