摘要Background At present,heat stress(HS)has become a key factor that impairs broiler breeding industry,which causes growth restriction and poor meat quality of broilers.Selenium(Se)is an excellent antioxidant and plays a unique role in meat quality improvement.Recent years,nano-selenium(NanoSe)has received tremendous atten-tion in livestock production,due to its characteristic and good antibacterial performance in vitro.Here,we developed the heat stressed-broiler model to investigate the protective effects of NanoSe on growth performance and meat quality of broilers and compare whether there are differences with that of other Se sources(Sodium selenite,SS;Sele-noyeast,SeY;Selenomethionine,SeMet).Results HS jeopardized the growth performance and caused poor meat quality of breast muscle in broilers,which were accompanied by lowered antioxidant capacity,increased glycolysis,increased anaerobic metabolism of pyruvate,mitochondrial stress and abnormal mitochondrial tricarboxylic acid(TCA)cycle.All Se sources supple-mentation exhibited protective effects,which increased the Se concentration and promoted the expression of sele-noproteins,improved the mitochondrial homeostasis and the antioxidant capacity,and promoted theTCA cycle and the aerobic metabolism of pyruvate,thus improved the breast muscle meat quality of broilers exposed to HS.However,unlike the other three Se sources,the protective effect of NanoSe on meat quality of heat stressed-broilers was not ideal,which exhibited limited impact on the pH value,drip loss and cooking loss of the breast muscle.Compared with the other Se sources,broilers received NanoSe showed the lowest levels of slow MyHC,the highest levels of fast MyHC and glycogen,the highest mRNA levels of glycolysis-related genes(PFKM and PKM),the highest protein expression of HSP60 and CLPP,and the lowest enzyme activities of GSH-Px,citroyl synthetase(CS)and isoci-trate dehydrogenase(ICD)in breast muscle.Consistent with the SS,the Se deposition in breast muscle of broilers received NanoSe was lower than that of broilers received SeY or SeMet.Besides,the regulatory efficiency of NanoSe on the expression of key selenoproteins(such as SELENOS)in breast muscle of heat stressed-broilers was also worse than that of other Se sources.Conclusion Through comparing the meat quality,Se deposition,muscle fiber type conversion,glycolysis,mitochon-drial homeostasis,and mitochondrial TCA cycle-related indicators of breast muscle in heat stressed broilers,we found that the protective effects of organic Se(SeY and SeMet)are better than that of inorganic Se(SS)and NanoSe.As a new Se source,though NanoSe showed some protective effect on breast muscle meat quality of heat stressed broil-ers,the protective effect of NanoSe is not ideal,compared with other Se sources.