Ratriyanto , A., Indreswari, R., & Sunarto. (2014). Effects of Protein Levels and Supplementation of Methyl Group Donor on Nutrient Digestibility and Performance of Broiler Chickens in the Tropics. International Journal of Poultry Science, 13(10), 575–581. https://doi.org/10.3923/ijps.2014.575.581