Effects Of Different Heat Stress Level On Broiler Meat Quality And Mechanism

The global population is predicted to grow to over 9 billion by the middle of 21 st century,with 70% of people living in urban areas,and food demand is projected to grow by 70% by 2050.Climate change presents a series of challenges for global animal agriculture.The increasing of population brings the development of food industry,one of them is chicken industry.In China,people prefer chicken meat rather than other red meat,since it has good tenderness and its low price.However,the broiler's meat quality is more unstable with red meat.In China,The occurrence rate of PSE-like meat reaches 23.39 in summer(L?53).In Brazil,it reaches 10.20%(L?49).The problem of PSELike meat causes great damage to meat processing industry.One of the happening reasons of PES-Like meat is acute heat stress.The purpose of this experiment is to study the effects of different heat stress level on broiler meat quality and the mechanism.AA broilers were selected as the experimental material and divided into seven different group:(1)36°C for 1 h,(2)36°C for 2 h,(3)38°C for 1 h,(4)38°C for 2 h,(5)40°C for 1 h(6)40°C for 2 h,and(7)unstressed control group(25°C).Then broilers were processed laboratory slaughter process.Routine meat quality indicators were measured such as meat color,water holding capacity,protein solubility and muscle ultrastructure.Metabolic indicators were also measured like pH value,lactic acid,glycogen content and AMPK activity.The main results of this study are as follows:As the heat stress level increased,the breast meat quality changed.Under 36?,Broilers meat lightness,cooking loss,protein solubility was worse than control group.However,as the heat stress temperature increased,this characteristic got relieved and disappeared.Acute heat stress increased breast meat glycolysis rate and AMPK activity,then fasted muscle pH value decline.On the other hand,acute heat stress increased breast meat glycogen content.The glycogen content increased as the heat stress level increased.Acute heat stress changed the breast muscle ultrastructure.HS(36?,2h)and HS(38?,2h)group myofibril fragmentation degree increased.However,as the heat stress level increased,the myofibril fragmentation degree relieved and the myofibril interval significant increased.Faster pH decline rate may play an important role in meat quality,that's why 36? group got the worst meat quality.As the heat temperature increased,we found AMPK activity lower than 36? group,then the pH decline rate got down,relatively,the meat quality indicators became close to control group.Heat stress temperature is an main factor than heat stress time.As the temperature went high,broilers blood cortisol concentration increased,at the meantime,the effect of heat stress induce PSE-like meat got weekend.However,the specific mechanism is still not clear.