Effercts Of Breed And Nutritional Level On Development Patterns Of Myofibre

Developmental patterns of myofibre type composition in longissimus dorsi muscle were compared between Duroc,Landrace and Yorkshire crossbred pigs(DLY pig)and China Rongchang Pig(CRP)by determining the ratios of mRNA abundances of four isoforms of MyHC with Multiplex-PCR.Phenotypic correlations for pork quality was determined.The thesis aimed to reveal the regulation between nutrition and meat quality,and lay the foundation for the interaction of molecular nutrition and function genes of meat quality.Thus in order to prove references for the revision of feeding standards.This experiment selected ninety DLY pig and CRP respectively which is 8kg.Each breed slaughtered six pigs at 10kg,and the others were randomly divided into two groups with two feeding standards(one group fed NRC feeding standard(1998),while the other fed the feeding standard for Rongchang pigs(GB 7223～1987)).Each group had six duplicates with seven swines.One pig in each duplicates was slaughtered at 20kg,35kg,50kg,80kg and 120kg respectively(132 pigs).Meat samples from these pigs were tested in muscle color,pH1,pH24 and marbling.Methods followes RNA extraction of longissimus dorsi muscle,the mRNA levels of four isoforms of MyHC with RT-Multiplex-PCR.The results as follows:(1)There were no significantly differences in the developmental patterns of DLY pig and CRP between the two nutritional levels..(2)The results show that the development patterns of myofibre type distribution of DLY pig and CRP in different weight were developmental.The MyHCⅠfibres of DLY pig and CRP decreased significantly(P＜0.01),and MyHC 2b fibres increased remarkably(P＜0.01)by gain weight. Howerev,the strain differences in the composition of myofibres in longissimus dorsi muscle appear after 10kg,and MyHCⅠ,2a and 2b fibres were remarkably changed in DLY pig and CRP.(3)Muscle pH value were negatively correlated with type glycolytic.The results show a negative correlation was observed between muscle pH1 and type 2b fibres(r=-0.608,P＜0.05)at 35kg of DLY pig and CRP at 50kg,muscle pH1 were negatively correlated with type 2b fibres(r=-0.612,P＜0.05).The fibre type slow-oxidative were positively correlated with Hunter Color a values.A positive correlation was observed between Hunter Color a values and fibre typesⅠ(r=0.682,P＜0.05)of CRP at 80kg.