Kappa-casein genotyping in tropical milking Criollo and its association to milk production and composition

Caseins are abundant proteins in milk and found in four types (alpha(S1), alpha(S2), beta, and kappa). There is substantial variation in the allelic and genotypic frequencies of the kappa-casein gene in different cattle breeds, although the tropical milking Criollo (TMC) has not yet been investigated. The aim was to determine the allelic and genotypic frequencies in the kappa-casein gene for two alleles (A and B) in TMC and further investigate its association to milk production and composition. A total of 180 TMC females were genotyped from blood samples. kappa-Casein genotyping was performed using restriction fragment length polymorphism (RFLP) after polymerase chain reaction (PCR)-based amplification of genomic DNA. Allele frequencies were 0.39 for A-allele and 0.61 for B-allele (P < 0.05). Genotype frequencies were 0.09 (AA), 0.60 (AB), and 0.31 (BB) (P < 0.05). The kappa-casein genotype in TMC cows did not affect milk yield or composition. In sum, the TMC has high frequencies of the B-allele and AB/BB genotypes, although there are no association of such genotypes and milk traits.