Effect And Mechanism Of Garcinol On Postmortem Muscle Glycolysis And Meat Quality Of Finishing Pigs

Postmortem muscle glycolysis is the biochemical basis for the formation of pork quality characteristics,which directly affects the meat quality traits such as p H,color,water holding capacity and tenderness.The aim of this study was to investigate the effect and mechanism of dietary garcinol on postmortem muscle glycolysis and meat quality of finishing pigs.A total of 80 Duroc×Landrace×Yorkshire（79.40±1.60 kg）ternary hybrid boars with good health and similar body condition were assigned into 4 groups at random,including control group and three dosage of garcinol groups（200,400 and 600 mg/kg）.Each group includes 5 replicates（4 pigs per replicate）.The trial period was 52 days.At the end of the experiment,the longissimus dorsi muscle was collected to detect meat quality,postmortem muscle lactate content,glycolytic enzymes acetylation levels,enzyme activities and related gene expression,so as to explore the regulatory effect and mechanism of garcinol on postmortem muscle glycolysis and pork quality.The main results are as follows:（1）The effect of garcinol on growth performance and carcass traits of pigs.The ADFI among control group and garcinol groups was not apparently different（P>0.05）.However,compared with the basal diet,the three dosage of garcinol all increased the ADG（P<0.05）.The ADG in low and middle dosage of garcinol groups was no significant difference（P>0.05）,but was lower than that in high dosage of garcinol group significantly（P<0.05）.Compared with control group,low dosage of garcinol has no signficant effect on F/G（P>0.05）,however,middle and high dosage of garcinol reduced the F/G markedly（P<0.05）.Garcinol showed no remarkable impact on the final weight,carcass weight,slaughter rate,longissimus dorsi area and backfat thickness at the last rib（P>0.05）,but markedly reduced the backfat thickness at the first rib and last lumbar vertebrae as well as the average backfat thickness（P<0.05）.（2）The results of pork quality showed that compared with the basic diet,low and middle dosage of garcinol showed no significant effect on the p H_45min（P>0.05）,but 600mg/kg garcinol increased the p H_45minsignificantly（P<0.05）.The three dosage of garcinol all increased the p H_24h,a*,b*_24h and reduced the L*_24h,water dripping loss and shear force dramatically（P<0.05）.The L*_45min,b*_45min and cooking loss were not significantly different in the control group and garcinol groups（P>0.05）.Besides,the pork quality between 200 and 400 mg/kg garcinol groups was not obviously different（P>0.05）,and the p H_45min,p H_24h,a*_45min,tenderness and water-holding capacity in low and middle dosage of garcinol groups were significantly lower than those in 600 mg/kg garcinol group（P<0.05）.（3）The results of muscle antioxidant indexes and myosin heavy chain（My HC）m RNA expression of finishing pigs showed that the content of muscle MDA in the garcinol groups was markedly reduced than that in the control group（P<0.05）.The activities of GPx,CAT and T-AOC were markedly increased in garcinol groups（P<0.05）.The acitivity of SOD among control group,low and middle dosage of garcinol goups was no statistical difference（P>0.05）,but was lower than that in the 600 mg/kg garcinol group significantly（P<0.05）.Compared with the basal diet,three dosage of garcinol all improved the expression of IIa m RNA notably（P<0.05）,but had no marked impact on the m RNA expression of My HC I and IIx（P>0.05）.200 mg/kg garcinol showed no notable impact on the m RNA expression of My HC IIb（P>0.05）,but middle and high dosage of garcinol significantly reduced the expression level of My HC IIb（P<0.05）.（4）The results of muscle chemical composition and postmortem lactate content showed that in comparison with the basal diet,the three dosage of garcinol significantly increased the content of myoglobin（P<0.05）,but had no marked impact on the content of muscle moisture,intramuscular fat（IMF）,crude protein（CP）,glycogen and glucose+6-phosphate（P>0.05）.Comparison with the control group,the three dosage of garcinol all significantly decreased the content of muscle lactate in postmortem 45 min and 24 h（P<0.05）.The muscle chemical composition and postmortem lactate in 200 and 400mg/kg garcinol groups was no significant difference（P>0.05）,but the lactate content in postmortem 45 min and 24 h were significantly higher than those in 600 mg/kg garcinol group（P<0.05）.（5）The results of the m RNA expression,activity of PCAF and acetylation levels of glycolysis enzymes in the muscle of finishing pigs showed that the PCAF m RNA expression was not significantly different in control group and 200 mg/kg garcinol group（P>0.05）.However,middle and high dosage of garcinol significantly decreased the m RNA expression level of PCAF（P<0.05）.Moreover,dietary supplementation of garcinol significantly decreased the activity of PCAF in the muscle of finishing pigs（P<0.05）.Compared with the control group,the acetylation of PFKFB3,GAPDH and PGK1 were significantly decreased with the increase of garcinol dosage added（P<0.05）.（6）The results of the m RNA expression and enzyme activities of glycolysis enzymes showed that compared with the control group,the three additive dosage of garcinol had no significant effect on the m RNA expression of glycolytic enzymes PFKFB3,PFK1,GAPDH,PGK1 and lactate dehydrogenase A（LDHA）（P>0.05）,but significantly decreased the enzyme activities of PFKFB3,PFK1,GAPDH and LDHA（P<0.05）.The enzyme activity of PGK1 in 200 mg/kg garcinol group and control group was no significantly difference（P>0.05）.but was significantly lower than that in middle and high dosage of garcinol groups（P<0.05）.In conclusion,dietary garcinol can increase the muscle antioxidant ability,and can decrease the activities of PFKFB3,PFK1,GAPDH and PGK1 by inhibiting PCAF and PCAF-mediated acetylation of glycolytic enzymes,thus slowing down postmortem muscle glycolysis and improving the pork quality.