Analysis of Ancestral Inbreeding Across Main Founders and Ancestors in the Polish Simmental Cattle Population
Simple Summary Inbreeding—the mating of closely related animals—is a growing problem in many livestock breeds, including Simmental cattle raised in Poland for both meat and milk production. When animals share many common ancestors, their offspring more often inherit identical copies of genes, which can reduce health, fertility, and overall productivity. Because importing bulls and cows from abroad was expected to introduce new, unrelated genetics, inbreeding levels in Polish Simmental cattle were assumed to remain low. Our study found, however, that inbreeding has been steadily increasing in younger cows. By tracing the ancestry of the entire Polish Simmental population, we identified the key ancestors responsible for this rise. Our findings show that a small number of highly influential ancestors—many of them imported animals—are closely related to the local population, meaning that importing more animals from the same genetic lines does not reduce inbreeding. We therefore recommend that breeders carefully check the genetic background of imported animals before use, selecting only those that are genuinely unrelated to the existing Polish population. This approach can help preserve the genetic diversity, health, and long-term productivity of Simmental cattle in Poland.