The first Brazilian bovine breed: structure and genetic diversity of the Curraleiro Pé-duro

Abstract

Background: The production of animal-based foods from native breeds have a synergistic relationship with the regional culture, the local climate, and mainly the maintenance of alternative genetic resources for a system with a lower environmental impact. Thus the efficiency of conservation and production depends on assessing the variability of these local breeds. In the case of Curraleiro Pé-duro cattle, the most adapted individuals have undergone natural selection over five hundred years in the Brazilian savannas, mating with little or no human interference. The peculiarities of these biomes, where the regional flora is the food base and cattle is raised in extensive areas, likely influenced the genetic composition of the different groups that make up the first cattle breed of Brazil.

Methods: To evaluate the composition, diversity, variation, differentiation, and genetic structure of the populations studied, samples of hair follicles from 474 individuals of different animal categories (calves, yearlings, heifers, cows, and bulls) from three farms, defined as subpopulations "A", "B", and "C", were collected. The animals were genotyped for 17 microsatellite markers using a DNA sequencer. After verification of monomorphic alleles, alleles outside the expected size range, and for the presence of stutter bands, the results were subjected to statistical analysis.

Results: The markers used were suitable for the proposed application with a mean Polymorphism Information Content (PIC) of 0.62. On average, the effective alleles were 4.25 per marker, with mean heterozygosities of 0.74 (observed and expected), which was lower in herd A (0.70) in comparison to herds B (0.77) and C (0.74). The analysis of molecular variance (AMOVA) revealed a higher rate of variation within herds (98.5%) and lower among herds (1.5%) (F_STranging from 0.00723 and 0.03198; p-values < 0.05). However no significant differences among herds where found with the Mantel test based on geographic distances. The formation of genetic clusters of all animals sampled with the software Structure resulted in minimum cluster values, with two main genetic groups (K = 2) observed among the evaluated animals. Therefore, based on PIC and heterozygosity values, a wide genetic diversity was observed, despite little differences in population structure (AMOVA, F_ST, and Structure results) among sampling sites.

Keywords: AMOVA; Microsatellites; Native breed; Slatikin’s genetic distance.

Figure 1. Verification of better genetic grouping of Curraleiro Pé-duro individuals as a function of Evanno’s Delta K values (Evanno, Regnaut & Goudet, 2005).

Figure 2. Main groups of subpopulations of Curraleiro Pé-duro cattle detected by the method of determining clusters of genetic similarity.