MUC1 is a transmembrane glycoprotein expressed in the male and female reproductive tracts, which plays a broad functional role in reproduction. An important feature of MUC1 is the presence of a VNTR polymorphism in the extracellular domain that is associated with the function of the molecule. In view of its role in reproduction, the aim of the present study was to analyze the effect of the length of the MUC1 VNTR on the early puberty phenotype in Nelore cattle. A total of 230 heifers were studied, including 77 sexually precocious heifers and 153 regular heifers. The genotype was identified by PCR and the allele and genotype frequencies between the two groups (precocious or regular heifers) were compared by Fisher’s exact test using the population differentiation module of the GenePop program, version 3.4. The associations between VNTR polymorphism and early puberty were analyzed as discrete data using the SAS GenMod procedure of SAS. Higher frequencies were observed for allele 1, 2, and 3, with allele 1 being predominant in both groups. No significant differences in allele or genotype frequencies were observed between precocious and regular heifers. The analyses using ANOVA and orthogonal contrasts suggest that the MUC1 VNTR variation is not associated with early puberty in cattle. Previous studies regarding the MUC1 polymorphism in Nelore cattle suggested that the high frequency of the 1 allele is a characteristic of Brazilian Nelore cattle.
