2.2. Diet and treatmentsCorn-soybean meal basal layer diet was formulated. The basal dietcontaining approximately 1400 mg choline/kg was prepared frommajor feed ingredients plus supplemental choline chloride. The cholinecontents of corn and soybean meal in the formula were derived fromZhai et al. (2013), and rice bran from NRC (1994). The basal diet wasalso supplemented with 0.75 mg folic acid and 0.015 mg vitamin B12/kg. These met the nutrition recommendation guideline (A HendrixGenetics Company, 2009). Because methionine has an important role asmethyl donor such as choline that in turn can generate PC from PE, thecontent of methionine must be maintained at the same content in alldiets to prevent its influence on the result. The calculated value ofmethionine in all diets was 0.42 mg/kg while the recommendationguideline of methionine is at 0.40 mg/kg.