The aim of this study was to investigate the effects of osteocalcin ( OCN ) on fatty liver hemorrhagic syndrome ( FLHS ) in aged laying hens. Thirty 68-week-old White Plymouth laying hens were randomly assigned into conventional single-bird cages, and the cages were randomly allocated into one of 3 treatments (n = 10): normal diet (ND + vehicle, ND + V ), high-fat diet (HFD + vehicle, HFD + V ), and HFD + OCN (3 μg/bird, 1 time/2 d, i.m.) for 40 d. At day 30, oral glucose tolerance tests ( OGTT ) and insulin tolerance tests ( ITT ) were performed. At the end of experiment, the hens were euthanized followed by blood collection. The plasma aspartate transaminase ( AST ), alkaline phosphatase ( ALP ), total cholesterol ( TC ), triglyceride ( TG ), low-density lipoprotein cholesterol ( LDL-C ), and high-density lipoprotein cholesterol ( HDL-C ) were measured using an automatic biochemistry analyzer. Pathological changes in the liver were examined under both light and transmission electron microscopes. The plasma inflammatory factors including interleukin-1 ( IL-1 ), IL-6, and tumor necrosis factor-alpha ( TNF-α ) were analyzed by ELISA, and the gene expressions of these inflammatory factors in the liver were analyzed by real-time PCR. The level of oxidative stress was evaluated using malondialdehyde ( MDA ) and glutathione peroxidase ( GSH-Px ) assay kits, respectively. The results showed that HFD + V hens had more severe liver hemorrhage and fibrosis than ND + V hens ( P < 0.05). The ultramicrostructural examination showed that hepatocytes of HFD + V hens exhibited necrotic pyknosis showing great intracellular electron, mitochondrial swelling, shrunk nucleus, and absence of autolysosomes. Osteocalcin mitigated HFD + V–induced pathological changes in aged laying hens. High-fat diet + OCN hens had higher insulin sensitivity; lower liver concentrations of MDA ( P = 0.12) but higher GSH-Px ( P < 0.05); and lower blood TNF-α concentrations ( P < 0.05) and mRNA expressions ( P < 0.05) than HFD + V hens. These results suggest OCN functions in preventing the FLHS process in old laying hens through inhibiting excessive energy diet-induced metabolic disorder, oxidative stress, and related pathological damage.

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