Abstract #T44

# T44
Polymorphism in the β-casein gene in Zebu dairy cattle.
A. H. N. Rangel*1, L. G. Zaros1, M. S. Silva2, D. M. Lima Júnior3, J. G. B. Galvao Jr.4, S. A. Urbano1, 1Universidade Federal do Rio Grande do Norte, Macaiba, RN, Brazil, 2Programa de Doutorado Integrado em Zootecnia, Universidade Federal do Ceará, Fortaleza, CE, Brazil, 3Universidade Federal de Alagoas, Arapiraca, AL, Brazil, 4Instituto Federal de Educaçao, Ciencia e Tecnologia do Rio Grande do Norte, Ipanguaçu, RN, Brazil.

The allelic frequency of the CSN2 gene in Gyr and Guzerat pure breed animals was studied in an experiment conducted at the Rio Grande do Norte State, in Brazil, with 88 Guzerat and 68 Gyr animals of different categories. Hair samples from the cow tail tassel were collected and the DNA extraction was performed from the hair follicles, following the precipitation method with salt. Nucleotide sequence readings of the amplified fragment for the β-casein gene (A1 and A2) were aligned and edited. Allele frequencies (Xi) for β-casein alleles (1) and genotypic frequencies for the genotype (2) were obtained using the equations: Xi = 2nii + ∑nij / 2n;xij = nij / n, in which nii and nij correspond to the number of homozygotes and heterozygotes observed in the i allele, respectively; and n corresponds to the number of individuals analyzed. Using the Hardy-Weinberg theorem, expected genotypic frequencies at equilibrium were estimated from expanding the binomial: (xi + xj) = xi2 + 2xixj + xj2, where xi2 is the expected frequency of homozygous for allele i; 2xixj is the expected frequency for heterozygotes ij; and xj2 is the expected frequency of homozygous for allele j. It was found that Guzerat animals had a higher amount of heterozygous animals compared with Gyr of the population (Table 1). None of the evaluated animals presented homozygosity for A1. The allelic frequency of A2 allele and the genotypic frequency of A2A2 genotypes for β-casein gene in the assessed Zebu breeds indicate that these breeds may produce less allergenic milk for individuals who are sensitive to β-casein protein. Table 1. Allelic and genotypic frequencies for the A1 and A2 alleles of the CSN2 gene in Gyr and Guzerat breeds
BreedAllelic frequencyGenotypic frequencyHWE1P-value2
A1A2A1A1A1A2A2A2
Gyr0.020.9800.040.960.070.99
Guzerat0.030.9700.070.930.230.97
1HWE = Hardy-Weinberg equilibrium. 2Chi-squared test.

Key Words: allelic frequency, nucleotide sequence, Zebu breed