Assessing genomic taurine/zebuine admixture in the southern meat cattle based on microsatellite markers

Abstract

Hybridization between wild and domestic bovine species occurs worldwide either spontaneously or by organized crossing. The Southern Meat (SM) cattle is a composite developed by crossing Cuban zebu (Bos indicus) with different cattle breeds (Bos taurus) – local Red Steppe, Hereford, Charolais, Santa Gertrudis, Dairy Shorthorn. The main aim of this work was to study the genetic structure of the Southern Meat breed (SM) cattle and to assess the taurine/zebuine admixture in the SM population using microsatellites. A set of 192 heifers representing the SM cattle (the ‘Askaniiske’ State Pilot Farm, Kherson region, Ukraine) was included in the study during 2013-2014. Based on the origin of the individuals studied, all heifers were attributed to two groups according to the different degree of Zebu blood: the LZ group (≤ 3/8 percent Zebu blood; n=100) and the UZ group (>3/8 percent Zebu blood; n=92). Ten bovine autosomal polymorphic microsatellite loci (BM1818, BM1824, BM2113, ETH3, ETH10, INRA023, TGLA53, TGLA122, TGLA227 and SPS115) were genotyped to estimate various parameters of genetic diversity. The total number of genotype estimates ranged substantially over loci from 18 (locus BM1824) to 37 (locus INRA023), giving a mean number of 27.9 ± 1.96 genotypes per locus. Overall, one hundred and four alleles were observed across the 10 microsatellite markers examined, with allelic diversity (the average number of observed alleles per locus) of 10.4 ± 0.76. Significant difference (P<0.05-0.001) was found between the LZ and UZ groups with regard to distribution of allele frequencies across all loci. The values of Ae, Ho, He and Fis in two SM cattle groups did not differ significantly (a non-parametric paired Wilcoxon’s test; for all cases P>0.05). At each locus some alleles were identified that were present at higher frequencies in the LZ group and absent or present at relatively lower frequencies in the UZ group, or vice versa. Evidence for an association between specific alleles at every locus with B.indicus/B.taurus breed was assessed by using a Logistic Regression model. Significant relationship was discovered only for two loci, TGLA227 (χ2=22.30; P<0.001) and ETH10 (χ2=27.70; P<0.001). It can be assumed that the TGLA227 (77 bp) and ETH10 (209-211 bp) alleles among the SM cattle examined individuals were inherited from a B.indicus ancestor. On the other hand, the TGLA227 (89 bp) and ETH10 (217-219 bp) alleles which prevails among individuals in the LZ group were inherited from a B.taurus ancestor. Thus, the SM cattle presented with high level of taurine/zebuine admixture, which is consistent with the breeding history.