Studies On Meat Quality Traits And Their Molecular Genetic Mechanisms In Laiwu Pigs

Laiwu Black is one of Chinese natjve pig breeds, which has excellent germplasm properties such as high prolificacy and good meat quality. Laiwu pigs and western pig breeds were selected to study the essentials of meat quality traits and their molecular genetic mechanisms. The aim of this thesis is to lay the scientific foundations for use of Laiwu Black and MAS in modern high quality pig breeding.Sixty pigs, including pure Laiwu Black, pure Large Yorkshire, 1/2 Laiwu, 3/4 Laiwu and 1/4 Laiwu, were selected to investigate the effects of graded proportions of Laiwu Black genes on carcass and meat quality performance. Results indicated that different consanguinity had significant effect on carcass weight, carcass length (CL), ham percentage (HP) and backfat thickness (BT) (P<0.05), and had highly significant effect on longissimus dorsi area (LDA) and lean percentage (LP) (P<0.01). Furthermore, CL, HP, LDA and LP tended to increase gradually, but BT tended to decrease gradually as Laiwu Black genes decreased. For meat quality properties, different consanguinity had significant effect on meat color, marbling score, dry matter and crude protein content (P<0.05), and had highly significant effect on water loss, drip loss and intramuscular fat (IMF) content of muscles (P<0.01). Compared with the muscle of Large Yorkshire, that of Laiwu Black and its crossbred pigs were bright red in meat color, high in water holding capacity and abundant in IMF. On the whole, the carcass quality tended to increase, but the meat quality tended to decrease gradually as Laiwu Black genes decreased. Analysis showed that the magnitude and direction of the heterosis effects were different among combinations. Moreover, there were higher heterosis which were beneficial on improving carcass and meat quality in the 1/4 Laiwu than that in the other crossbreed. Results implied that to give attention to both quantity and quality, Laiwu Black surely has usable precious value in superior pig production. Commercial crossbred pigs should have about 1/4 of Laiwu Black genes.Eighty-four Laiwu Black (LB) (weight of 30-90kg) and Xin Laiwu (XL) pigs (weight of 40-100kg) were used to study the development changes of meat quality and intramuscular collagen and the relationship between them. The results showed as follows: Weight of LB had significant effects on muscle total collagen (TC) (P<0.01), insoluble collagen (IC) (P<0.01), collagen solubility (CS) (collagen cross-links) (P<0.05), shear force (SF) (P<0.05), marbling score (MS), dry matter (DM) and IMF (P<0.01). Weight of XL had significant effects on muscle TC (P<0.05), soluble collagen (SC) (P<0.05), IC (P<0.01), CS (P<0.01), MS (P<0.01), cooking percentage (CP) (P<0.05) and Napole yield (NY) (P<0.01), DM (PO.05) and IMF (PO.01). These two breeds, on the whole, had same development changes of IMF and collagen. Increased weight of pigs was associated with an increase inmuscle TC, IC, IMF and water binding capacity (WBC), but tended to be related with a decrease in muscle SC, CS and tenderness. Compared with Xin Laiwu, Laiwu Black were generally higher in muscle TC, CS, IMF, MS, CP, NY and water holding percentage (WHP), but lower in muscle drip loss (DL) and SF. It was proved that as the whole muscle, bundles of fibers and individual muscle fibers are surrounded by a delicate collagenous network like sheaths, the increase of quantity of collagen and its cross-links was found to be highly correlated to WBC improvement (PO.05) and toughness (P<0.01), whereas, the increase of IMF content was strongly correlated to WBC improvement (P<0.05) but not to toughness.223 pigs, including Laiwu Black and four western pig breeds (Landrace, Large Yorkshire, Hampshire and Duroc), were selected to detect genetic variation of H-FABP gene by PCR-RFLPs and its association with IMF content. The results showed that for the H-FABP gene, there was one polymorphic Hinfl site in the 5'-upstream region, whereas there were one Hae III and one Hinfl (marked as Hinfl * ) polymorphic site in the second intron, respectively. The three PCR-R...