Transcriptomic Analysis Reveals The Molecular Mechanisms By Which House Feeding And Grazing Affect The Meat Quality And Flavor Formation Of Black Goats

Lamb is rich in high-quality protein,and since 2015,the demand for lamb in China’s market has been steadily increasing.According to FAO statistics,from 1994 to 2021,the total global production of goat meat reached 130 million tons,of which China’s goat meat production reached 49 million tons,accounting for 36.98%,ranking the first in global goat meat production,thus enhancing the flavor and nutritional value of goat meat has significant market prospects.Currently,goats in China are raised in two ways: grazing and housing.Since grazing goats are more active and feed on a wide variety of forages,the meat is relatively strong and compact,with a better taste and texture,and the meat quality and flavor are significantly better than that of housing goats.With the improvement of living standard,people gradually prefer to eat goat meat raised by grazing.However,there is a lack of systematic studies on the mechanism of grazing rearing affecting meat quality and flavor of goat meat.In this study,we systematically analyzed the gene expression in rumen,liver and jejunum of grazing and housed goats by transcriptome analysis,and conducted a preliminary study on the molecular regulatory mechanisms affecting meat flavor.The results of the study are as follows:1.mRNA transcriptome analysis of rumen,liver and jejunum of grazing and housing black goats: rumen,liver and jejunum samples were collected from grazing and housing black goats,respectively,and total RNA was extracted and sequenced.The results showed that 13521 transcripts were identified in the rumen of black sheep,and 331 differentially expressed genes(DEGs)were screened.Analysis of the screened DEGs revealed that arachidonic acid metabolism and unsaturated fatty acid biosynthesis in the rumen of black sheep were significantly up-regulated in the grazing feeding group.A total of 12737 transcripts were identified in the liver and 1910 DEGs were screened.The enrichment analysis revealed that DEGs were mainly enriched in redox processes,fatty acid biosynthesis pathway and glutathione metabolism.A total of 14720 transcripts were identified in jejunum and 1344 DEGs were screened.Enrichment analysis revealed that DEGs were mainly enriched in PPAR signaling pathway,arachidonic acid metabolism and linoleic acid metabolism pathway.The analysis found that DEGs in all three tissues were enriched in fatty acid metabolism and amino acid metabolism related pathways,indicating that different feeding methods significantly affected fatty acid metabolism pathways in black goats,and ultimately led to differences in meat quality and flavor.2.Analysis of rumen,liver and jejunum lncRNAs in grazing and housed sheep: 37,65 and 176 lncRNAs were identified in rumen,jejunum and liver tissues of sheep under different feeding methods,respectively.We found that MSTRG.29720.2,MSTRG.50001.1,MSTRG.50002.1 and MSTRG.50004.1and their targeting SLC1A1 and FABP5 genes were associated with the formation of meat flavor in black goat.The formation of meat flavor was correlated.In this study,we revealed the molecular mechanism of grazing and housing that affects the meat flavor of black goats.The rumen of black goats digests and partially absorbs the fatty acids ingested into the body,and then the unabsorbed fatty acids enter the jejunum and are further absorbed into the blood by the intestinal epithelium,while the liver undergoes fatty acid synthesis by the action of fatty acid synthase(FAS),and we investigated this process by transcriptome in black goats in both feeding methods.We investigated the differences of gene expression patterns in rumen,jejunum and liver of black sheep in two feeding methods by transcriptome,and explored the key genes affecting flavor amino acid and unsaturated fatty acid contents,which provided an important theoretical basis for quality breeding of black sheep.