Changes of hepatic biochemical parameters and proteomics in broilers with cold-induced ascites

Ascites syndrome is still a problem for chicken industry in various parts of the world. Despite the intensive investigations of this syndrome for many years, its pathogenesis remains unclear. The objective of this study was to analyze the difference in hepatic proteomics between ascites and healthy broilers by two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS). Changes of biochemical parameters of liver and blood were also determined. The results indicated that red blood cell counts (RBC), hematocrit (HCT) and haemoglobin (HGB) of ascites broilers were significantly greater than healthy broilers. Hepatic malondialdehyde (MDA) level of ascites broilers was significantly increased, and the activity of total superoxide dismutase (T-SOD) was significantly decreased. Hepatic lactic acid (LD) level of ascitic broilers were significantly lower than healthy ones. Serum glucose and cholesterol level of ascites broilers were significantly increased, and serum globulin level was significantly decreased in ascites broilers. There was no significant difference in triglyceride (TG) and blood urea nitrogen (BUN) level. The activity of liver hexokinase (HK) and succinodehydrogenase (SDH) in ascites broilers was significantly decreased, and there was no significant difference in the activity of liver pyruvate kinase (PK) and Na+-K+-ATPase. The hepatic proteomics analysis showed that 18 proteins expression difference were identified between ascites and healthy broilers. These proteins were mainly involved in: 1) cytoskeleton; 2) glucose, lipids and amino acid metabolism; 3) cell secretion; 4) cell apoptosis; 5) signal transduction; 6) immune and inflammatory response; and 7) cellular redox homeostasis. Mitochondrial isoform phosphoenolpyruvate carboxykinase (M-PEPCK) mainly participates in gluconeogenesis of chicken liver. In conclusion, liver oxidative damage was significantly aggravated, but antioxidant capacity was decreased in cold-induced ascites broilers. Serum glucose level was significantly increased, with liver M-PEPCK expression higher in ascites broilers, which implied that some potential regulatory reagents may reduce ascites susceptibility and mortality under cold temperature by increasing liver gluconeogenesis level.