The methylation levels of genomes were compared in swine, cattle, sheep, rat, chicken and duck, using the methylation-sensitive amplification polymorphism technique (MSAP). The results showed that the methylation levels in genomes of the species investigated were mostly about 40–50% (except cattle); the methylation level varied in different species; the methylation pattern in various tissues of each species was specific; for the same species, the methylation level of the tissue genome was mostly higher than that of the blood genome; the difference of methylation level between birds and mammals was not significant, however mammals appeared to have a lower hemi-methylation frequency and higher full methylation frequency than birds.
