Population and genetic characterization of Blackbelly sheep in the Amazonian Savanna

Locally adapted sheep breeds represent valuable genetic resources for livestock under tropical climatic, nutritional, and health constraints. This study characterized the population structure and estimated genetic parameters for birth weight and FAMACHA (FAffa MAlan CHArt) score in Blackbelly sheep maintained in a conservation nucleus in the Amazonian Savanna of northern Brazil. Pedigree records from 371 animals and phenotypic records for birth weight (n = 274) and repeated FAMACHA scores (n = 482) were analyzed. Population structure parameters were estimated from genealogical data, and genetic parameters were obtained using Bayesian single-trait animal models. The pedigree was shallow (1.24 equivalent generations), with an effective population size of 40.76 and an average relatedness coefficient of 3.40%. Mean inbreeding was 0.80% but increased by 0.63% per generation. Birth weight and FAMACHA score averaged 2.36 kg and 3.15, respectively. Heritability was high for birth weight (0.47) and low for FAMACHA score (0.14). These findings underscore the importance of improving pedigree recording and implementing targeted mating strategies to mitigate inbreeding, preserve genetic diversity, and ensure the long-term sustainability of Blackbelly sheep in tropical systems of the Amazonian Savanna.