Abstract #W69

# W69
Admixture analysis in Brazilian synthetic cattle.
Marcos E. Buzanskas*1, Ricardo V. Ventura2, Tatiane C. S. Chud1, Daniel J. A. Santos1, Priscila A. Bernardes1, Thiago B. R. Silva1, Mauricio A. Mudadu3, Luciana C. A. Regitano3, Marcos V. G. Barbosa da Silva4, Changxi Li5, Flavio S. Schenkel2, Maurício M. Alencar3, Danísio P. Munari1, 1UNESP – Univ Estadual Paulista, Faculdade de Ciências Agrárias e Veterinárias, Jaboticabal, SP, Brazil, 2University of Guelph, Guelph, ON, Canada, 3Embrapa Southeast Livestock, São Carlos, SP, Brazil, 4Embrapa Dairy Cattle, Juiz de Fora, MG, Brazil, 5University of Alberta, Edmonton, AB, Canada.

The development of synthetic breeds in Brazil from crosses between Bos taurus indicus (Bti) and Bos taurus taurus (Btt) is very useful when it is desired to combine the fitness and carcass yield. The Canchim breed (CA), which has expected proportions of 62.5% Charolais and 37.5% zebu (Nellore breed), have been the focus of several studies because this breed has high carcass quality and adaptability to extensive production system. The aim of this study was to estimate the genetic composition in the Canchim breed using single nucleotide polymorphism (SNP) data. Canchim animals (285 individuals) were genotyped with the Illumina BovineHD BeadChip (777962 SNPs). To estimate the genetic contribution of Btt and Bti, 814 animals from the Nellore breed (NE) and 405 animals from the Charolais breed (CH) were genotyped with the Illumina BovineHD BeadChip and BovineSNP50 BeadChip (54609 SNPs), respectively. The PLINK v.1.9 software was used to combine the data, perform genotype quality control, and estimate the linkage disequilibrium (r2). The ADMIXTURE software was used to estimate the genetic contributions. Genotype quality control resulted in 283, 811, and 405 animals from the CA, NE, and CH breeds and 29716 SNPs. The genetic contributions of Btt and Bti in the Canchim breed were, in average, 72.5% and 27.5%, respectively. Minimum and maximum proportions of Btt and Bti ranged from 66.0% to 89.0% and 11.0% to 34.0%, respectively, in Canchim cattle. The differences between the expected proportions and the estimated proportions of Btt and Bti were due to the patterns r2, which are greater in shorter distances (0–0.04 Mb) for CH (0.20), followed by CA (0.16), and NE (0.15). When the r2 between adjacent SNPs are high, recombination rates should be low, which may be indicative of greater contribution of CH animals in the composition of CA breed. The maximum proportion of 16.0% of Btt was observed for NE, indicating remote crossbreeding, which could have contributed to higher Btt proportion in CA animals.

Key Words: beef cattle, genomics, genetic structure