Identification Of Candidate Genes And Selection Of Suitable Level For Diet Defatted Rice Bran Related To Drip Loss Of Suhuai Pork

Drip loss is an important factor in affecting pork quality.High drip loss could not only affect the pork quality,but also bring serious economic losses.Therefore,reducing muscle drip loss can effectively improve pork quality and pork economic value.Suhuai pig is a new breed with 25%Huai pig blood and 75%Large white blood.Suhuai pigs were used as experimental animals in this study to explore the factors affecting the drip loss of pork in both genetic and nutritional aspects to provide a theoretical basis for the improvement of pork quality.Firstly,we measured and analyzed the phenotypic variation of drip loss in Suhuai pig,and carried out the research on candidate genes affecting drip loss to find the molecular markers affecting drip loss of pork.Secondly,we studied the effect of dietary fiber level on the drip loss of Suhuai pig for the purpose to find a suitable dietary fiber level for keeping the drip loss of pork at a low level.The experiment results are as follows:1.Phenotypic determination and analysis of muscle drip loss in Suhuai pig populationThree hundred and one fattening Suhuai pigs were slaughtered and samples were selected for drip loss measurement in this research,the coefficient of variation of drip loss in Suhuai pig population was analyzed,and the effects of gender and age on the drip loss of Suhuai pork were compared.The results showed that the mean value of muscle drip loss was 1.83%,the maximum value was 5.95%,the minimum value was 0.20%and the coefficient of variation reached 67.88%.Among them,the average muscle drip loss of castrated boars(1.97%)was significantly higher than that of sows(1.29%)(P<0.01).In addition,muscle drip loss were extremely significant differences(P<0.01)among different age groups.Of them,the average muscle drip loss of the 6-month group was significantly lower than that of the 7-month group and the 8-month group(P<0.01),and the average muscle drop loss of the 7-month group was significantly lower than that of the 8-month group(P<0.01).2.Candidate gene polymorphism analysis and assocation between these genes and muscle drip loss in Suhuai pigsIn this study,Sangle sequencing was used to genotype the 5 candidate genes(MAMSTR,RYR1 RETN,PHKG1,PRKAG3)which related to drip loss in 301 Suhuai pigs.The mixed linear model of SAS 9.2 software was used to analyze the association between genotype and drip loss.The results showed that all the 5 candidate genes were polymorphic in Suhuai pig population.Among them,the mutation of C>T at rs337473375 locus of MAMSTR gene was extremely significantly associated with muscle drip loss(P<0.01),and CC was a favorable genotype.The mutation of C>T at rs344435545 locus in RYR1 gene and the mutation of A>G at rs697732005 locus in PHKG1 gene were also significantly associated with the drip loss of pork(P<0.05).There was a significant trend that the mutation of A>G at rs1108399 locus in PRKAG3 gene influence drip loss(P=0.070).While the mutation of G>A at rs327132149 locus in RETN genes could not influence muscle drip loss in Suhuai pigs.3.Effect of dietary defatted rice bran level on drip loss and PHKG1 gene expression in Suhuai porkIn order to study the effect of fiber level on the quality of Suhuai pork,35 castrated boars with same age and similar weight were selected and randomly divided into 5 groups and fed diets containing 0%,7%,14%,21%and 28%defatted rice bran respectively.All pigs were slaughtered after 28 days of the experiment.The muscle color(L*means brightness,a*means redness,b*means yellowness),pH value,drip loss,IMF and shearing force were measured.The results showed that the drip loss of Suhuai pork was lower at 7%and 14%of the defatted rice bran replacement level compared with the control group,respectively,and reached the lowest at the 21%defatted rice bran replacement level,and then increased.Therefore,we hold the view that the suitable dietary fiber level for high quality Suhuai pork was 21%of the replacement level of defatted rice bran.The shearing force of pork decreased linearly as the substitution level of defatted rice bran increasing(P<0.05).Cooked meat rate and pH24h showed a linear increase trend with the increase of the replacement level of defatted rice bran(P=0.061 and P=0.08,respectively).L*24 h presented a linear decreasing trend with the increase of the replacement level of defatted rice bran(P=0.085).Other meat quality indexes were not changed by the level of the replacement level of the diet defatted rice bran.Based on the result that 21%of the replacement level of defatted rice bran can reduce pork drip loss,and combine the important role of PHKG1 gene in the physiological process of drip loss and its association with drip loss in Suhuai pigs,the real-time quantitative PCR method was used to detect the relative expression of PHKG1 gene to studied the effects of dietry fiber level on PHKG1 gene expression.The result showed that the relative expression of PHKG1 gene in muscle of Suhuai pigs changed significant with the increase of the level of defatted rice bran(cubic,P<0.05)and tended to quadratic change(P=0.085).To sum up,this paper comes to the following conclusions:1.The mean value of muscle drip loss in Suhuai pig population was 1.83%,and the coefficient of variation in the population was large.Gender and age had significant effects on drip loss.2.The rs337473375 locus in MAMSTR gene,the rs344435545 locus in RYR1 gene and the rs697732005 locus in PHKG1 gene were significantly associated with Suhuai pork drip loss(P<0.05).3.The drip loss of Suhuai pork showed a quadratic change with the increase of dietary defatted rice bran(P<0.05),the relative expression of the PHKG1 gene in muscle also changed with the increase of dietary defatted rice bran(P<0.05)and tend to quadratic change(P=0.085),and the suitable dietary fiber level for high quality Suhuai pork was 21%of the replacement level of defatted rice bran.