Process of Introduction of Australian Braford Cattle to South America: Configuration of Population Structure and Genetic Diversity Evolution

SIMPLE SUMMARY: The Braford breed originated in the USA and Australia from a cross between the Brahman and Hereford breeds to obtain animals suitable for the subtropical climate and resistant to hoof diseases, eye cancer, and ectoparasites, mainly ticks. This resistance to ticks was what attracted the attention of South American breeders, who acquired animals from Australia. The first breeder to do so was Uruguay around 1970. From then on, the breed was distributed across Argentina, Paraguay, and Brazil. Each country has its own association of breeders, and each one keeps the herdbook of the breed where the animals are registered. Selective breeding was conducted, thereby shaping genetic diversity over the years. The analysis of the pedigree database allowed us to evaluate these changes and the evolution of diversity over time. The objective of the present work was to analyze the population structure of the Braford breed in four countries, the repercussions of founders and ancestors, and the parameters of genetic diversity to suggest effective strategies for Braford breeders. ABSTRACT: This study analyzes the evolution of the population structure and genetic diversity of Braford cattle in South America from 1949 to 2019 to suggest effective strategies for breeding in the future. The percentage of bulls historically increased. The average generational interval decreased to 11.78 years for the current population. Average inbreeding (F) and coancestry (C) are low and show a historically increasing trend (0.001% to 0.002%, respectively). The degree of nonrandom mating (α) increased from −0.0001 to 0.0001 denoting a change in the trend to mate similar individuals. The average relatedness coefficient (ΔR) increased in the current period from 0.002% to 0.004%. A single ancestor explained 4.55% to 7.22% of the population’s gene pool. While the effective population size based on the individual inbreeding rate (NeFi) was 462.963, when based on the individual coancestry rate (NeCi), it was 420.168. Genetic diversity loss is small and mainly ascribed to bottlenecks (0.12%) and to unequal contributions of the founders (0.02%). Even if adequate levels of diversity can be found, practices that consider the overuse of individual bulls (conditioned by nature or not), could lead to a long-term reduction in diversity. The present results permit tailoring genetic management strategies that are perfectly adapted to the needs that the population demands internationally.