Effects Of Dietary PUFA Composition On Growth Performances,meat Quality,Intestinal Flora And Metabolites In Heigai Pigs

The composition of dietary polyunsaturated fatty acids(PUFA)are closely related to human health and low n-6/n-3 PUFA ratio diets are more benefit.Pork is an important source of human dietary fatty acids,but due to the current farming methods,pork contain low n-3 PUFA content and high n-6/n-3 PUFA ratio.Therefore,how to improve the fatty acid composition and reduce the n-6/n-3 PUF A ratio of pork has become an important issue in the current farming and the food industry.Researches show that nutritional regulation technology is a reliable method that can improve the fatty acid composition of pork and meat quality.In addition,Chinese local breed pigs have certain advantages in meat quality and fatty acid composition.It is a great significance to improve the fatty acid composition of pork,especially the n-6/n-3 PUFA ratio,by using the advantages of Chinese local breeds of pigs and nutrition regulation technology.In this study,Shandong Heigai pigs were taken as the research object to investigate the effect of diet n-6/n-3 PUFA ratio on growth performance,meat quality,intestinal flora and its metabolites.A total of 54 Heigai finishing male pigs(body weight:71.59 ± 2.16 kg)were randomly divided into three treatments with six replications(three pigs per replication)and fed diets containing different n-6/n-3 PUFA ratios:8:1(treatment 1),5:1(treatment 2),and 3:1(treatment 3).The pigs were fed with the corresponding diet for 75 days(five days pre-feeding period and seventy days formal test period).At the end of the feeding period,6 pigs in each group were slaughtered,growth performance and meat quality indicators were measured,and longissimus dorsi muscle(LDM),subcutaneous fat(SAT),serum and colon contents were collected.The samples were subjected to qPCR,fatty acid composition determination,amino acid composition determination,16S rDNA sequencing and other related experiments.The main results are as follows:1.The study found that the pigs fed with different n-6/n-3 PUFA ratio diets has no significant differences on main carcass index and serum short chain fatty acids(SCFAs)composition of each group is not affected by the dietary PUFA composition.The content of total thyroxine(T4)and other hormones are increased(p<0.05),glucose and energy metabolism were promoted;and n-6/n-3 PUFA ratio of serum decreased(p<0.01),and n-3 PUFA content increased(p<0.01)with the decrease of dietary n-6/n-3 PUFA ratio.These results suggest that changing dietary PUFA composition may affect hormone levels and serum fatty acid composition(especially n-6 and n-3 PUFA composition).2.The pigs fed with different n-6/n-3 PUFA ratio diets has no significant differences on the main sensory meat quality indicators and comprehensive antioxidant capacity of LDM,but the pigs fed with lower n-6/n-3 PUFA ratio diets slow down the rate of decline in LDM pH(p<0.05).N-6/n-3 PUFA ratio of LDM and SAT decreased(p<0.01),and n-3 PUFA content increased(p<0.01)with the decrease of dietary n-6/n-3 PUFA ratio.Transcriptome sequencing and qPCR results showed that diets with low n-6/n-3 PUFA ratios significantly(p<0.05)down-regulated lipid-related genes(PLIN1,ACSS2 and ADIPOQ)and lipolysis-related genes(LIPE,ACADM,LEP and ACAT1),and significantly increased(p<0.01)the expression of UCP3(related to lipolysis).These results suggest that reducing the n-6/n-3 PUFA ratio of the diet can regulates glucose and lipid metabolism related genes,reduce the n-6/n-3 PUFA ratio of pork,increase the content of n-3 PUFA,and improve the fatty acid composition of pork.3.The 16S rDNA sequencing results showed that the three PUFA diets used in the experimenthad had no significant difference affect on the predominant flora and the Firmicutes/Bacteroidetes ratio of each group at the phylum level.However,the pigs fed with lower n-6/n-3 PUFA ratio diets show lower abundance of Cellulosilyticum(related to fiber degradation,p<0.01);and higher abundance of Christensenellaceae(negatively correlated with obesity,p<0.01)and Bacteroides and Alloprevotella(related to the production of SCFAs,p<0.01).Metabolomics results showed that compared with the treatment 1,the functions of the bacteria in the treatment 2 and the treatment 3 are enriched in "propionate metabolism"(p<0.05),"limonene and pinene degradation"(p<0.05)and "butyrate metabolism"(p<0.01).These results suggest that the composition of dietary PUFA may affect meat quality through changing intestinal flora to regulate fiber degradation,fat and fatty acid metabolism.4.We further carry out correlation analysis on meat quality,different bacterial genera and different metabolites,the results showed that △b and the ratio of n-6/n-3 PUFA in LDM and serum were positively correlated with the content of nutriacholic acid(p<0.05),and negatively correlated with ceanothenic acid and pelargonic acid content(p<0.05).The abundances of Bacteroides,Alloprevotella,Cellulosilyticum,Parabacteroides and Turicibacter are positively correlated with the content of nutriacholic acid(p<0.05),and negatively correlated with the content of pelargonic acid(p<0.05).These results suggest that changing the composition of dietary PUFA can regulate the changes in intestinal flora and metabolites that are significantly related to meat quality,then affects fatty acid metabolism and meat quality.In conclusion,this study used the Heigai pig as the experimental animal model,using microbiome,metabolome and other omics techniques to clarify the impact of dietary PUFA composition on the Heigai pig’s growth performance,meat quality,intestinal flora and its metabolites,and to reveale the relationship among meat quality,fat and fatty acid metabolism-related genes and intestinal flora.This research provides a certain theoretical basis and technical support for improving the fatty acid composition of pork through nutritional regulation,promoting healthy farming of Heigai pigs and producing characteristic and high-quality brand pork through nutritional regulation.