Studies On Biochemical And Molecular Mechanism Of Intramuscular Fat And Inosinic-5'-monophosphate Contents In Chicken Meat

This study evaluated the effect of mode of rearing on growth performance, carcass composition, meat quality, muscle fibers, activity of selected enzymes and expression of candidate genes in leg and breast muscle in Beijing-You chicken. Sixty females and sixty males, separated by sex, were allocated to 2 rearing treatments, caged and floor pens, at 56 d of age. The 30 birds per subclass (sex x rearing) were raised in the same room and fed the same diet. The chickens were killed at marketing age (120 d) and sampled to assess carcass composition, meat quality, muscle fibers, enzyme s activities and gene expression.Significant differences existed between breast and leg muscle.The ratio of white muscle fibers to total fibers in breast was high, but in leg was low. The content of shear stress and values of b and L in breast were higher than in leg, while pH and values of a was significantly lower.The content of inosine-5-monophosphate (IMP) was higher than in leg, while the content of intramuscular fat (IMF) was significantly lower.Activities of the enzymes LPL and CK were higher in leg,while ATP was lower in leg. The mRNA expression of H-FABP, LPL, HADH-β, CKMM, ACAA2 were all higher in leg, while that of ADSL was higher in breast. The correlation of mRNA expression of H-FABP, LPL, HADH-β, ACAA2 with the content of IMF was positive, while that of CKMM with the content of IMP was negative.Yield of breast or leg muscle was increased and abdominal fat accumulation or the content of IMF was decreased in free-range, compared with caged birds. Rearing in floor pens increased the content of IMP, but was disadvantageous with regard to shear stress in breast. In leg muscle, shear stress was increased. The ratio of white muscle fibers to total fibers in breast was decreased in favor of enhanced red muscle fibers. In addition, the expression of mRNAs for LPL and CKMM and the activity of CK differed with rearing mode. the mRNA expression of LPL, CKMM was all higher in free-rangeTo sum up, it is the key to the impact of the contents of IMF and IMP difference between breast and leg that metabolizing enzymes and candidate genes expression was differed.The metabolizing enzymes of ATP and the mRNA expression of candidate genes are key elements in different content of IMP and IMF.