1. The objective of the study was to investigate the susceptibility of young and older laying hens to
fatty liver-haemorrhagic syndrome (
FLHS) and to evaluate the reliability of different blood
lipid fractions for predicting or diagnosing
FLHS. 2. Forty young hens and 40 older hens were caged individually. Each group of hens was randomly allotted to four treatments for 21 days: either a control, an
oestradiol group, a high energy-
low protein diet (HELPD) group or a HELPD +
oestradiol group. Blood levels of
oestradiol,
triglyceride (TG),
cholesterol (CHOL),
high density lipoprotein-cholesterol (HDL-C) and
low-density lipoprotein-cholesterol (
LDL-C), liver total
lipids, hepatic haemorrhagic scores and productive performance were assessed. 3. In older hens, β-
oestradiol increased (P < 0.05) liver total
lipids, hepatic haemorrhagic scores and the incidence of
FLHS but reduced (P < 0.05) productive performance; however, such changes were not observed in young hens. 4. In two groups of hens, serum TG, CHOL and HDL-C levels were increased (P < 0.001) by β-
oestradiol. Hens with
FLHS had higher serum TG, CHOL and HDL-C (P < 0.001) than non-
FLHS birds in the older layer group of hens. 5. An interaction (β-
oestradiol × HELPD) (P < 0.05) for
LDL-C levels was observed in both groups of hens. In young hens, β-
oestradiol induced a decrease (P = 0.004) in serum
LDL-C levels but the effect was attenuated by HELPD. In older hens, HELPD caused an increase (P = 0.02) in serum
LDL-C although the effect depended on the presence of β-
oestradiol. 6. In conclusion, older layers were more susceptible to
FLHS than young layers after
oestradiol treatment. Blood TG, CHOL and HDL-C rather than
LDL-C levels can be used as a prediction tool for the overall susceptibility to
FLHS in older rather than young layers. There were interactions between
oestradiol and HELPD on blood
LDL-C levels in laying hens.