Effects And Mechanism Of Electrical Stunning On Meat Quality Of Broilers

Stunning can minimize the pain and suffering associated with slaughter,it has been viewed positively from the perspective of animal welfare.Stunning can reduce pre-slaughter stress and wing flapping of broilers during slaughter,and reduce carcass damage and improve postmortem meat quality.Water bath electrical stunning is currently the most widely used method for pre-slaughter stunning of poultry in commercial plants.It is convenient,economical,requires only a small space,and can be readily adapted to commercial processing plants.Water bath electrical stunning can be divided into high voltage low frequency and low voltage high frequency stunning according to the voltage and frequency.The current of high voltage stunning can lead to a serious caress damage of broilers,but low voltage high frequency stunning can reduce caress damage and improve post-mortem meat quality,so it will become a trend to sunning broiler in our country in the next few years.The effects of electrical stunning on final meat quality are dependent on the voltage,frequency,and duration used.Improper stunning parameters will increase pre-slaughter stress and carcass damage,and electrical stunning can affect the energy metabolism of post-mortem muscle,and then affect the enzyme activity,the degree of protein denaturation,cytoskeletal protein degradation,and finally affect the post-mortem meat quality.It is earlier to study sunning of broilers in abroad.But in our country,there only several people have studied it.At present,we don’t know how the broiler stunning has been used in our country,and what kind of electrical stunning parameters is suitable for our country broiler slaughter industry.It is unclear that how electrical stunning affects the post-mortem meat quality.Through investigation of the conditions of stunning broilers in our country,and optimize stunning parameters,and study the mechanism of the effects of electrical stunning on post-mortem meat quality,to provide a theoretical basis for broilers stunned before slaughter in this article.1.The investigation of stunning of broilers in China.Through field research and questionnaire of broiler slaughter and processing enterprise in our country,learn about our current technology status of stunning broilers.The stunning bath used in some enterprises is relatively backward.In some companies,there is not having arc on track in the up of stunning bath,and some companies only used a single electrode strip in electrical stunning bath.Most of the companies have not used darkroom to hang broilers,and about half of the companies have not used the darkroom bleeding.Only a few of the companies have been controlled the time after slaughter and before bleeding within 10 s.Even though the bleeding time is difference from 3 min to 10min,but more concentrated,most of the companies controlled bleeding time between 4min to 5 min.At present,it is vary widely of the stunning parameters used in our country,voltage from 30 V to 80 V is most of used,fixed-frequency 50 Hz is most of used,most of the companies controlled stunning time within 10 s.Carcass damage has seriously affected post-mortem meat quality.Reduce carcass damage is more and more important,with the increase of product segmentation.There is still no complete legislation on animal welfare in our country,and low voltage high frequency stunning can improve animal welfare,reduce carcass damage,and improve post-mortem meat quality.Low voltage high frequency stunning will be a main way in broiler slaughter companies in our country.2.Low voltage high frequency stunning parameter optimization.It is used to stun broilers for optimization stunning parameter by voltage(5 V,15 V,25V,35 V,45 V)and frequency(500 Hz,600 Hz,700 Hz,800 Hz,900 Hz).And it is used to determine optimum parameters range using voltage(10 V,15 V,20 V)and frequency(650 Hz,700 Hz,750 Hz)to stun broilers.The plasma corticosterone and lactic acid content in 5 V stunning group is higher than other groups.The wing is seriously damaged in 5 V,35 V and 45 V stunning groups.The carcass damage is not serious in 15 V stunning group.In 5 V and 45 V stunning groups,the pH during early post-mortem is lower,the protein solubility is lower,and the dripping loss is higher.The plasma corticosterone and lactic acid content in 500 Hz and 900 Hz stunning group is higher than other groups.The carcass damage is not serious in 700 Hz stunning group.In 500 Hz and900 Hz stunning groups,the pH during early post-mortem is lower,the protein solubility is lower,and the dripping is higher.The stunning parameter of voltage within 10 V to 20V and frequency within 650-750 Hz can improve post-mortem meat quality.3.The effects of electrical stunning methods on broiler meat quality:Effect on stress,glycolysis,water distribution,and myofibrillar ultrastructures.It is to verity the superiority of low voltage high frequency sunning parameter,through compare low voltage high frequency[LS,15 V(13-15 mA),750 Hz,10 s,DC],mid-voltage low frequency[MS,50 V(48-52 mA),50 Hz,10 s,AC],High voltage low frequency[HS,100 V,(106-110 mA),50 Hz,5 s,AC]and direct slaughter(NS).LS stunning can reduce the plasma corticosterone concentration,carcass damage and improve meat quality.Stunning methods does not affect plasma glucose and lactic acid.LS and HS can significantly reduce glycogen decomposition and lactic acid accumulation during early post-mortem period.And the pH during early post-mortem period is higher in LS and HS groups.The protein solubility is significantly higher in LS and HS groups.The population of T21 in muscle following LS and HS treatment was significantly higher than that for MS and NS treatment.However,the population of T22 following NS and MS treatments was significantly higher than with LS and HS treatments.There were no difference about meat color and 24 h post-mortem muscle pH value.Electron microscopy of LS and HS samples revealed good preservation of normal structures,and they have a shorter sarcomere length,but they have a higher shear force.4.Effects of physical restraint and electrical stunning on plasma corticosterone,postmortem metabolism,and quality of broiler breast muscle.For this study,160 Arbor Acres broilers were randomly categorized into 2 replicate pens(80 broilers per pen)and each pen was randomly divided into 4 groups,free struggle(FS,hung upside down 30 s and slaughter),physical restraint(PR,physical restraint,hung upside down 30 s and slaughter),free struggle and electrical stunning(FSES,hung upside down 20 s,electrical stunning[15 V,750 Hz,10 s]and slaughter),and physical restraint and electrical stunning(PRES,physical restraint,hung upside down 20 s,electrical stunning[15 V,750 Hz,10 s]and slaughter).Physical restraint can significantly reduce plasma corticosterone.The plasma corticosterone is highest in FS group.It indicated that wing flapping can increase pre-slaughter stress.Wing flapping can accelerate glycogen decomposition and lactic acid accumulation during early post-mortem period.And then it reduced the pH value during the early post-mortem period.Wing flapping can accelerate ATP,ADP decomposition and AMP accumulation during early post-mortem period.But it does not affect the final pH,ATP,ADP,and AMP.It has a higher red value,dripping loss,cooking loss in wing flapping group.But it is not affect L*value and b*value.Wing flapping during slaughter can early activateμ/m-calpain,and make it autolysis,finally reduce meat shear force.5.Effects of physical restraint and free struggle on calpain activity and cytoskeletal protein degradation of broiler M.pectoralis major.For this study,20 Arbor Acres broilers were randomly divided into two groups free struggle(FS,hung upside down 30 s and slaughter),physical restraint(PR,physical restraint,hung upside down 30 s and slaughter).Wing flapping during slaughter can accelerate lactic acid accumulation and pH decline during early post-mortem period,but it not affect the final pH and lactic acid.Wing flapping during slaughter can early activateμ/m-calpain and accelerate desmin,titin,nebulin degradation,and accumulation of the 30kDa degradation of troponin-T.