| The cold-tolerance temperature of beef cattle was 15℃,and the heat-tolerance temperature of beef cattle was 25℃.It was reported that in summer,the high temperature can easily lead to the occurrence of heat-stress of the beef and it had big influences on the growth performance and the metabolism of the beef cattle.Because of its good nutritional value,more and more consumers pay more attention to the meat quality of the beef cattle.Understanding the adapt characteristics of different breed of beef could provide more scientific reference the feeding and management of the beef,and revealing the characteristics and meat quality of different varieties beef could provide more scientific references for people.At present,the study about heat-tolerance and lipid metabolism between JinJiang and Simmental beef had not been reported.The objective of this study was to compare the growth performance,heat-tolerance and lipid metabolism between JinJiang and Simmental beef in summer,to reveal the ability of adapt and lipid metabolism in the process of growth and development.In addition,the meat quality and characteristics of skeletal muscle fibre were carried out to preliminary explore the possible mechanism between JinJiang and Simmental beef.1.Comparative study on the heat-tolerance and lipid metabolism characteristics between JinJiang and Simmental beef in summer.A total of 30 beef cattle were allotted into five groups as the weights,with three JinJiang beef and three Simmental beef per treatment.The experiment was carried out in summer,and to measure the environment temperature and humidity,at the same time,measuring the respiratory frequency and rectal temperature.Then collecting the blood and lymphocyte of blood were used to measure the serum hormone,oxidation and the expression of HSP70 and HSF1.Samples from subcutaneous adipose were collected for subsequent analysis.The results were shown as follow.(1)The environment index results showed that the bam temperature was more than 35℃ at all times during the experiment and at 14:00 every day the temperature humidity index(THI)was the highest.The temperature humidity index was still more than 74 during the experiment;the beef had been under the heat stock environment.The respiratory rate and rectal temperature were higher in the high weights in JinJiang beef and Simmental beef.At 14:00 every day the respiratory rate was the highest.The respiratory rate of Simmental beef was higher than the JinJiang beef(P<0.05);the rectal temperature had no significance in the 150 and 200 kg groups between JinJiang beef and Simmental beef(P>0.05);the rectal temperature had significance in the 250,300 and 350 kg groups between JinJiang beef and Simmental beef(P<0.05),the rectal temperature was higher in Simmental beef.The results of hormones and antioxidant index showed that the serum T3/T4 content decreased with the weight gain;and the T3/T4 content in Simmental beef was lower than JinJiang beef(P<0.05).Compared with the JinJiang beef,the COR content in serum was higher,and when the weight was more than 250 kg groups,the COR content in Simmental beef still increased(P<0.05).The T-SOD activity decreased with the weight gain and the T-SOD activity in Simmental beef were lower than JinJiang beef in the 300 and 350 kg(P<0.05).The MDA content increased with the weight gain,and when the weight was more than 200 kg groups,the MDA content was higher than JinJiang beef(P<0.05).The GSH-Px activity decreased with the weight gain,the GSH-Px activity in Simmental beef was lower than JinJiang beef in the 250,300 and 350 kg groups(P<0.05).The CAT activity decreased with the weight gain,the CAT activity in Simmental beef was lower than JinJiang beef in the 250,300 and 350 kg groups(P<0.05).The expression of HSF1 and HSP70 was lower than JinJiang beef in 300 and 350 kg groups(P<0.05).(2)The GLU content of blood result showed that there was significant difference in the stage of 300 and 350 kg groups between JinJiang beef and Simmenatal beef,the GLU content was higher than JinJiang beef(P<0.05);the BUN and CRE had no significant difference(P>0.05).The TC and CHO content were higher than JinJiang beef before the weight reached 250 kg(P<0.05),after 250 kg the TC and CHO content were lower than JinJiang beef(P<0.05);the change of HDL/LDL content were same as TC and CHO.The NADPH and ACC of blood results showed that there were significant difference in the stage of 300 and 350 kg between JinJiang beef and Simmenatal beef,the content was lower than JinJiang beef(P<0.05),the LEP,ADIPO and INS were same as ACC.The gene expression of C/EBPa and PPARγ had significantly difference between two kinds of beef in the same weight stage,in the stage of 200 and 250 kg weight,the expression of C/EBPα and PPARγ were lower than Simmenatal beef(P<0.05)and in the stage of 300 and 350 kg,the expression of C/EBPα and PPARγ were higher than Simmenatal beef(P<0.05);the protein expression result showed that in the stage of 300 and 350 kg,the expression of C/EBPa and PPARY were higher than Simmmenatal beef(P<0.05).In the stage of 200 and 250 kg weight,the gene expression of LPL and PPARa were higher than Simmenatal beef(P<0.05),and the expression of LPL and PPARa were lower than Simmenatal beef(P<0.05)in the 300 and 350 kg weight,the protein expression result showed that in the stage of 300 and 350 kg,the expression of LPL and PPARocwere lower than Simmenatal beef(P<0.05).2.The meat quality and mechanisms of myofibre type characteristic between JinJiang beef and Simmental beef.On the day of slaughter,after a 12-h fast,three JinJiang beef and three Simmental beef were selected,weighted individually and slaughtered.Samples from Longissimus muscle,biceps femoris,semitendinosus,intramuscular fat and subcutaneous fat were selected for subsequent analysis.The results were shown as follow.(1)The water and crude fat content were higher than Simlental beef in LM and BF(P<0.05).There was no significant difference in crude protein and calcium content in LM and BF between the two groups(P>0.05).There was a significant difference in phosphorus content in LM and ST(P<0.05).The pH was higher than Simmental beef in LM and BF(P<0.05).The meat color(b*)was higher than Simmental beef in LM and BF(P<0.05);the meat color(L*,a*)was higher than Simmental beef in LM and ST(P<0.05);and the cooking loss was higher than Simmental beef in LM and BF(P<0.05).The hardness and gumminess were higher than Simmental beef in LM(P<0.05),and the chewiness was well than than Simmental beef in LM and SF(P<0.05).The sringiness and cohesiveness had no significant differences in JinJiang beef and Simmental beef(P>0.05).The composition of fatty acids in different muscle and adipose tissue had some differences,the big difference in two kinds breeds was in IMF,the ratio of C18:lcis-9,SFA and MUFA had significant differences in IMF(P<0.05).Compared with Simmental beef,the MUFA was higher;the ratio of C18:0 and SFA were lower in LM5 IMF and ST of JinJiang beef(P<0.05).In addition,we found that the ratio of SFA was higher and the MUFA was lower in BF of JinJiang and Simmental beef.(2)The activities of CS and HAD in LM and the BF of JinJiang beef were significantly lower than those in the Simmental beef(P<0.05);and the activity of LDH was significantly higher than that in the Simmental beef(P<0.05);there was no significant difference in ST between JinJiang beef and Simmental beef(P>0.05).Compared with Simmental beef,the expression of MyHC-Ⅰ.MyHC-ⅡⅢa were higher in the LM and BF in JinJiang beef(P<0.05);The expression of MyHC-Ⅱb was lower than in the LM and BF(P<0.05).The expression of MyHC-Ⅱx was lower in LM of JinJiang beef compeared with Simmental beef(P<0.05),and there was no significant difference in BF and ST between JinJiang beef and Simmental beef(P>0.05).The expression of PGC-1a in LM and BF of JinJiang beef was higher than those of Simmental beef(P<0.05);there was no significant difference in ST between JinJiang beef and Simmental beef(P>0.05).At the same time,the expression of Sox6 and Sp3 were lower than those of Simmental beef(P<0.05);there was no significant difference in ST between JinJiang beef and Simmental beef(P>0.05).The muscle fibre diameter in LM of JinJiang beef was lower than Simmental beef(P<0.05);the muscle fibre density in LM of JinJiang beef was higher than Simmental beef(P<0.05).The muscle fibre type results showed that the ratio of Typel and Typella in LM and BF of JinJiang beef were higher than Simmental beef(P<0.05),and had no significant difference in ST(P>0.05).The fibre density of Typel and Typella in LM was higher than Simmental beef(P<0.05),and the fibre density of Typellb was lower than Simmental beef(P<0.05);The fibre density of Typelin BF had no significant difference(P>0.05)3 the fibre density of Type Ⅱb had a significant difference(P<0.05);There was no significant difference in ST between JinJiang beef and Simmental beef(P>0.05).By chemical staining of ATPase,it was not to distinguish the type Ila fibres in the BF between JinJiang beef and Simmental beef.As stated above,the conclusions are as follow:1)When the weight was more than 250 kg,the respiratory rate and rectal temperature of Simmental beef were significantly higher than JinJiang beef,and the tolerance to high temperature was poor.In order to promote the body heat and maintain the body temperature balance in JinJiang beef,the contents of T3,T4 decreased and the COR increased;and there was no this advantage in Simmental beef.Compared to Simmental beef,the body antioxidant system in JinJiang beef could help the body to resist the heat stress.2)In summer,the lipid metabolism was different between JinJiang and Simmental beef.With the weight gain,the lipid deposition of JinJiang beef enhanced;while the Simmentalbeef was affected by the high temperature and humidity at 300 and 350 kg groups,the lipid deposition was weak,the lipid decomposition enhanced.3)The water content and crude fat content in the longissimus muscle(LM)of JinJiang beef were significantly higher than those of Sinmental beef;and the loss of cooking was significantly lower than that of Sinmental beef;the color L*and the redness a*value were relatively high;the L*value of ST was lower than the Simmental beef;Compared with JinJiang beef,the muscle of Simmental beef contained more polyunsaturated fatty acids(PUFA).4)The results of muscle fibre classification showed that the ratio of fermentation type fiber in LM and BF in JinJiang beef was more than Simmental beef,and the composition of muscle fibre type played an important role in regulating the meat quality of the muscle between JinJiang and Simmental beef.At the same time,the activity of muscle metabolism enzymes had significantly difference between JinJiang and Simmental beef,and played an important role in the formation of different muscle fibre types.Compared with Simmental beef,the up-regulation of MyHC-1 and the down-regulation of MyHC-Ⅱb in LM of JinJiang beef were regulated by the expression of PGC-1α、Sox6 and Sp3,indicating that the genes of PGC-1α,Sox6 and Sp3 have played certain regulatory roles on the development of different muscle fibre type. |
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