Transposable elements (TEs) are targets for early nutritional effects on epigenetic gene regulation. This study shows that dietary methyl donor supplementation in a/a dams alters the phenotype of their A^vy/a offspring via increased CpG methylation at the A^vy locus. The epigenetic metastability of the A^vy transposable element (IAP) renders it susceptible to early nutritional influences. The A^vy allele, which contains an IAP insertion, exhibits probabilistic CpG methylation, leading to phenotypic variability. Maternal supplementation with folic acid, vitamin B12, choline, and betaine increases methylation at the A^vy locus, shifting offspring coat color toward the pseudoagouti phenotype. This suggests that early nutrition can influence epigenetic gene regulation, potentially affecting adult health. The study also demonstrates that A^vy methylation is maintained throughout development and into adulthood, indicating that early nutritional effects can persist. The findings highlight the role of TEs in epigenetic inheritance and suggest that dietary influences on methylation may have unintended consequences on human health. The study underscores the importance of understanding how early nutrition affects epigenetic regulation, particularly in relation to transposable elements, which are abundant in the human genome. The results provide evidence that epigenetic changes induced by nutrition can influence gene expression and contribute to chronic disease susceptibility.Transposable elements (TEs) are targets for early nutritional effects on epigenetic gene regulation. This study shows that dietary methyl donor supplementation in a/a dams alters the phenotype of their A^vy/a offspring via increased CpG methylation at the A^vy locus. The epigenetic metastability of the A^vy transposable element (IAP) renders it susceptible to early nutritional influences. The A^vy allele, which contains an IAP insertion, exhibits probabilistic CpG methylation, leading to phenotypic variability. Maternal supplementation with folic acid, vitamin B12, choline, and betaine increases methylation at the A^vy locus, shifting offspring coat color toward the pseudoagouti phenotype. This suggests that early nutrition can influence epigenetic gene regulation, potentially affecting adult health. The study also demonstrates that A^vy methylation is maintained throughout development and into adulthood, indicating that early nutritional effects can persist. The findings highlight the role of TEs in epigenetic inheritance and suggest that dietary influences on methylation may have unintended consequences on human health. The study underscores the importance of understanding how early nutrition affects epigenetic regulation, particularly in relation to transposable elements, which are abundant in the human genome. The results provide evidence that epigenetic changes induced by nutrition can influence gene expression and contribute to chronic disease susceptibility.