Investigation Of Factors Contributing To The Incidence Of DFD Beef And Analysis Of Relationship Between Ultimate PH And Blood Biochemical Variables

Recent years,the yield and consumption of beef gradually increased in our country.With the improvement of living standard,people paid more attention to beef quality than quantity,and increasingly demand for high-quality beef became the collective goal for both consumers and meat industry.The greatest problem that beef cattle industry faced at present was DFD beef.DFD?Dark,Firm and Dry?beef was also called dark cutting beef,which exhibited a dark,purplish red to almost black lean color and a dry,often-sticky lean surface.Due to high ultimate pH,DFD beef had a greater ability to support microbial growth and a reduced shelf life.However,meat industry did not attach importance to the defect of DFD beef.The discounts given to dark cutting carcasses had become a major issue to the cattle slaughter plants.The objective of the first part of this study was to investigate the incidence of DFD beef in Shandong province,and find out pre-slaughter factors affecting the incidence of DFD beef in this area,using the pH₂₄?6.10 in the Longissimus dorsi muscle after post-mortem 24h as the DFD beef identification standard.Pre-slaughter stress was closely related with meat quality.Under stressful situations,the physiological response may influence the rate and extent of muscle metabolism,resulting in inferior beef quality.Some studies had demonstrated that stressors such as transport and lairage may affect the concentration of plasma cortisol,glucose,lactate,creatine kinase,lactate dehydrogenase,haptoglobin and serum amyloid A protein at exsanguination.Pre-slaughter stress was the main cause of DFD beef,and every procedure before slaughter may impact the blood biochemical indicators in cattle to some degree.Therefore,the objective of the second part of this study was to analyze the relationship between ultimate pH and stress-related exsanguination blood variables,finding out blood indicators that could predict DFD beef.In this study,the main results were as follows:1.The average incidence of DFD beef in Shandong province reached 18.03%,while the incidence of four cattle slaughter plants A?B?C?D were 31.87%?5.76%?20.20%?12.21%,respectively.The percentages of DFD beef differed significantly between plants?P<0.05?partially due to different management philosophies or to structural attributes or workers operating specification of the plants.2.The primary pre-slaughter management factors affecting the incidence of DFD beef in Shandong province were slaughter season,carcass weight,slaughter time and stocking density.Transport duration,lairage time,cattle gender and workers operating specification were the primary causes leading to the high incidence of DFD beef in plant A.3.The level of plasma cortisol,glucose,lactate,creatine kinase and lactate dehydrogenase were significantly different among three pH groups?P<0.05?.But the concentration of haptoglobin and serum amyloid A protein showed no significant differences among three pH groups?P>0.05?.4.The concentratiion of plasma cortisol,glucose,lactate,creatine kinase,lactate dehydrogenase,haptoglobin and serum amyloid A protein were clearly different between different breeds?P<0.05?.5.Measuring blood cortisol,glucose,lactate,creatine kinase,lactate dehydrogenase levels at exsanguination may be value of in the identification of DFD beef.