Abstract: The experiment was conducted to investigate the effect of betaine against fatty liver hemorrhagic syndrome(FLHS) in laying hens. One hundred and twenty Hy-line brown laying hens at the age of 300 days were randomly assigned to 3 groups，with 4 replicate pens per group and 10 laying hens per pen，and a feeding experiment was conducted with them for 60 days. The laying hens were fed with either normal diet(ME 11.30 MJ/kg and CP 17.20%)，high energy-low protein diet(ME 12.81 MJ/kg and CP 13.04%) or the high energy-low protein diet plus 1000 mg/kg betaine. Feed and water were provided for ad libitum consumption and the birds received light of 16 h a day. Eight hens from each group were selected on 1st，30th，and 60th days to collect samples including serum，liver and abdominal fat，respectively. The concentration of serum lipids，rate of liver fat and abdominal fat，laying performance and histopathologic changes were investigated to determine the effect of betaine against FLHS. The results showed that compared with the control group，feed the laying hens with high energy-low protein diet for 30 days could induce FLHS，and feeding for 60 days could lead to severe FLHS. Compared with the high energy-low protein group，feed the laying hens with high energy-low protein diet plus 1000 mg/kg betaine for 30 days significantly prevent the inducion of FLHS，but its preventive effect decreased obviously after feeding for 60 days.

Key words: betaine; laying hens; fatty liver hemorrhagic syndrome