Demographic Analysis of Sixteen Iberian Sheep Breeds Based on Pedigree Data

The Iberian Peninsula hosts a rich diversity of sheep genetic resources shaped by contrasting environments, historical management practices, and varying levels of endangerment. This study provides a comprehensive demographic characterisation of 16 Iberian sheep breeds (12 autochthonous and 4 integrated) using complete pedigree records supplied by breeders’ associations. Population structure was evaluated through census composition, population fragmentation, trends in sire and dam registrations, reproductive patterns, gender ratios, pedigree completeness, and generation intervals. Marked differences were observed among breeds. Integrated breeds consistently exhibited the highest pedigree completeness and a more intensive reproductive structure, characterised by fewer breeding animals but a higher number of offspring per parent. In contrast, many endangered Spanish breeds showed incomplete pedigree records, fewer registered sires and dams, unbalanced sex ratios and prolonged use of older breeding animals, indicating greater demographic vulnerability. Portuguese local breeds displayed more complete pedigree records, together with relatively high numbers of offspring per parent and/or extended reproductive use of breeding animals. Most breeds showed generation intervals close to four years, although longer intervals were observed in the most endangered populations. These findings highlight substantial differences in demographic structure and pedigree quality among Iberian sheep breeds, providing a demographic baseline to improve pedigree recording and support future conservation and breeding strategies, while reinforcing the role of breeders’ associations in preserving the genetic diversity.