Formation of functional and technological properties of pork by the influence of vitamin d3 on the differential maternal level of pigs

Abstract

The thesis is devoted to providing development and scientific justification of meat production technology with improved functional and technological properties at the stage of embryonic development (or at the stage of formation of pig offspring). Pork quality is related to human health and is affected by many factors. The distribution and deposition of adipose tissue are the key factors affecting pork quality, and the fat content can affect the meat quality of pigs by changing the juiciness, tenderness, flavor and palatability of pork. The first part introduces the factors that affect the formation of meat quality from the aspects of fat formation and its regulation, VD3 physiological function and lipid metabolism, maternal nutrition level affecting the development of adipose tissue and skeletal muscle, animal meat quality characteristics and its influencing factors. The study was conducted to investigate the effects of maternal VD3 status during pregnancy on meat quality attributes, technological properties, and processing performance in offspring pigs by feeding trials, slaughter experiment, and meat quality analysis technology. The objective of this study was meat production technology with given functional and technological properties, the level of VD3 in sows during pregnancy, lipid metabolism and the quality of offspring meat, and to supply scientific basis and implementation plan for early nutritional regulation technology of pork quality characteristics in offspring pigs. The second part expounds the scientific problems, clarifies the selection of research objects and directions, and puts forward the scientific methods of applied research. According to the research purpose of the experiment, a complete work plan was formulated, including feeding experiment, slaughtering experiment, analysis technology of potential factors related to meat quality characteristics, physical and chemical indexes of meat quality and relevant methods of storage capacity, in order to determine the best test scheme and implementation conditions. In order to achieve this test task, the research method and technical route were confirmed and described in detail. The third part presents the results of the effect of VD3 on the potential food factor of pork. It was found that at the age of 28 days, the concentrations of serum FT3, IGF-I and FT4 and the expression of PPARγ in LD group were higher than those in ND group and HD group, while the expression of ZFP423 and VDR, serum 25 (OH) D, leptin and insulin levels in LD group were significantly lower than those in ND group (P<0.05). In addition, the FAS/HSL mRNA expression ratio and FAS expression of piglets in HD group were higher than those in LD group and ND group (P<0.05). At 150 days of age, compared with the offspring of ND and HD groups, the LD offspring had higher FAS/HSL mRNA expression ratio and FAS mRNA expression in subcutaneous adipose tissue, higher HSL mRNA expression in the longissimus dorsal muscle, and lower FAS/HSL mRNA expression ratio in the longissimus dorsal muscle. In addition, the average back fat thickness (ABFT), carcass fat, serum leptin and insulin levels of LD group were higher than those of ND or HD groups, while the levels of serum triglycerides (TG), free fatty acids (FFA) and intramuscular fat (IMF) were lower. Additionally, IMF content in offspring was negatively correlated with FAS/HSL mRNA expression ratio, while carcass fat content and ABFT in offspring were positively correlated with FAS/HSL mRNA expression ratio. At the same time, the carcass fat content of offspring pigs was positively correlated with FAS mRNA expression, while ABFT was negatively correlated with FAS mRNA expression. Maternal high-dose VD3 supplementation decreased drip loss, shear force, total saturated fatty acids (SFA) content and n-6:n-3 ratio, while increased marbling score, subjective color score, longissimus muscle area, total monounsaturated fatty acids (MUFA) content, polyunsaturated fatty acids (PUFA) content, and the PUFA: SFA ratio. Maternal high-dose VD3 can significantly reduce the shear force, drip loss, total n-6: n-3 ratio and total saturated fatty acid (SFA) content of offspring pigs, and significantly increase the subjective color score, marbling score, total polyunsaturated fatty acids (PUFA) content, total monounsaturated fatty acids (MUFA) content, longissimus dorsi muscle area and the total PUFA: SFA ratio. Through the study of potential food factors affecting pork quality, we found that Maternal VD3 status during pregnancy have long-lasting impact on meat quality function and technological properties in offspring pigs. High-dose VD3 maternal feeding can improve the pork quality function and technological properties of offspring by regulating key genes and serum hormones related to adipose tissue deposition. By adjusting the maternal VD3 level during pregnancy, the pork quality characteristics of offspring were improved, and the scientific feeding scheme of VD3 in early pregnancy sows was optimized. The fourth part presents the results of physical-chemical indicators of meat quality and its ability to be stored. The quality characteristics of longissimus dorsi muscle of offspring pigs during post slaughter storage showed that the water holding capacity (WHC) and pH value of HD group were higher than those of LD group, while the relaxation time of T21 in HD group was lower (P<0.05); Compared with ND group, the shear force in HD group was lower, while that in LD group was higher (P<0.05), Compared with LD group, the a* values in HD group and ND group were higher, while the b*, L* values and T22 relaxation time were lower (P<0.05). At the same time, postmortem storage after slaughter, the pH value in ND group, WHC in LD group, a* and L* value in ND and LD groups were decreased, but the b* value in ND and LD groups, T22 relaxation time in LD, ND and HD groups were increased (P<0.05). The quality characteristics of the longissimus dorsi muscle of the offspring during frozen storage showed that the cooking loss, thawing loss, T22 and T21 relaxation time, b*, L*values of the longissimus dorsi muscle of the offspring increased significantly (P<0.05), while the shear force and a * values of the longissimus dorsi muscle of the offspring decreased significantly (P<0.05). In addition, the thawing loss, b* and L* values, T22 relaxation time and shear force of longissimus dorsi muscle in LD group were higher compared with that in HD group (P<0.05). Meanwhile, compared with LD and ND groups, the offspring of HD group had lower T21 relaxation time and cooking loss of longissimus dorsi muscle (P<0.05), while LD group had lower a* value compared with HD and ND groups during frozen storage (P<0.05). The quality properties of pork batters of offspring during cold storage period showed that compared with LD group, the L*value, cooking loss, T22 and T21 relaxation time of HD group were lower, while hardness, a* value, springiness, cohesiveness, and chewiness in pork batters of HD group were higher (P<0.05). Additionally, b* values and cooking loss of ND and LD groups, T22 relaxation time and TPA index of LD, ND group and HD group increased with cold storage, while L* and a* values of ND group and LD group decreased with cold storage (P<0.05). It is hereby proved that maternal high-dose VD3 (3200 IU/kg basal diet) supplementation could improve meat quality function and technological properties, and prolong the freezing storage time of pork, and shelf life of pork and pork batters in offspring. The fifth part presents the recommendations for improving the technology of meat production with given functional and technological properties. The 41st day gestation sow is the key window period for regulating the quality function and technical characteristics of offspring pork. From the 41st day of pregnancy to the farrowing period of sows, adjusting the level of VD3 supplementation to 3200 IU/kg basic diet can significantly improve the quality characteristics and production performance of offspring pork.