We assessed the polymorphism of 10 microsatellites in Brazilian Nellore cattle (Bos indicus) using a commercial multiplex system. Allele frequencies, polymorphism information content, heterozygosity and exclusion probability were calculated. Allele frequencies revealed that in the sample analyzed the markers were not equally polymorphic. The exclusion probabilities and the polymorphism information content of some loci in Nellore cattle were lower than in Bos taurus breeds. When all the microsatellites were considered the combined exclusion probability was 0.9989. This multiplex analysis can contribute toward pedigree information, adequate genetic improvements and breeding programs.

Allelic frequencies at 12 loci (five blood groups: C, D, K, P, and U; and seven protein polymorphisms: Al, A1B, Es, Gc, Hb, PGD, and Tf), are given for two Brazilian horse breeds: Mangalarga Marchador and Mangalarga. The high genetic identity value found (96.0%) is consistent with their common origin, although, at some point of the development of Mangalarga Marchador, Mangalarga separated from the original stock. The expected average heterozygosity was higher in Mangalarga Marchador. The populations presented genetic differentiation, as shown by the statistically significant value of F ST. The nonsignificant F IS values showed that there was no appreciable consanguineous mating in any of the two populations. Exclusion probability calculated for the 12 loci was 87.0% and 86.5% for Mangalarga Marchador and Mangalarga, respectively. No genetic equilibrium was observed in the A1B, Tf, and Es loci of Mangalarga Marchador. The frequencies of blood factors A, Q, and T were calculated.