Abstract

CAMPOS, Jorge; VARGAS, Bernardo; CAMACHO, Jorge  and  CRUZ, Argerie. Identity and parentage testing in registered Brahman cattle of Costa Rica. Agron. Costarricense [online]. 2018, vol.42, n.1, pp.49-62. ISSN 0377-9424.  http://dx.doi.org/10.15517/rac.v42i1.32197.

In genetic evaluation programs, the correct identification of the individuals of the population and the certainty of their kinship relationships is indispensable. The objective of this study was to implement identity verification and paternity tests using 18 microsatellite markers, in registered Brahman cattle from Costa Rica. Genetic parameters were calculated from the analysis of 950 DNA samples (7 sires, 788 cows and 155 offspring) collected during years 2015/2016, from 13 herds with registered cattle. Average observed and expected heterozygosity were 0.67 and 0.70, respectively. The fixation index was 4%, with significant deviations of the Hardy Weinberg equilibrium in 9 of the 18 loci. All markers except ETH225 had polymorphic information content greater than 0.50. The combined probability of identity with all markers was 2.4×10-17 for randomly selected individuals and 2.6×10-7 for full siblings. The combined probabilities of exclusion were greater than 0.999. All these parameters presented satisfactory values for the accomplishment of tests of identity and paternity. Next, paternity confirmation tests were performed on 137 offspring with reported father and/or mother from 3 herds. Paternity rejection rates based on the exclusion principle (at least 2 discordant loci) vs. critical likelihood values were, respectively: 18.2% vs. 24.1% for mothers, 14.0% vs. 12.5% for father, and 34.6% vs. 26.3% for trios. There were significant differences between herds for the percentage of paternity rejection, ranging from 15.6 to 39.4% in mothers, 0 to 30% in fathers, and 19.5 to 31.8% in trios. The need for greater control in mating and recording of genealogical information in these herds is demonstrated.

Keywords : Microsatellite; exclusion probability; likelihood ratio.

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