Effect of fructooligosaccharides and antibiotics on laying performance of chickens and cholesterol content of egg yolk.

1. Nine hundred and sixty 25-week-old Lohmann Brown layers were randomly divided into 5 groups with 216 layers in each group. Layers in group one were fed a control diet, group 2 received the control diet plus 20 mg/kg zinc bacitracin and 4 mg/kg colistinsulfate, and the remaining three groups received control diet plus 2000, or 4000, or 6000 mg/kg fructooligosaccharide (FOS). 2. The results showed improvements in egg production, feed consumption and feed conversion of layers when 2000 mg/kg FOS was added to the diets. 3. The results also showed some additional improvements in the group supplemented with 2000 mg/kg FOS, including increases in egg shell thickness, yolk colour and Haugh unit, and decreases in yolk cholesterol concentration. 4. However, larger (excessive) doses of FOS did not improve the performance of layers.