| Black goat is a kind of ruminant livestock with important economic value,and goat meat has high nutritional value.At present,there are mainly two feeding methods of Guangxi black goats: house feeding and grazing,and the prices of mutton produced by the two feeding methods are different in the market.In order to explore the difference in meat quality between house feeding and grazing black goats and the potential mechanism causing the difference,this experiment was conducted through multi-omics research.The research results are as follows:(1)Study on the differences in meat physiology,biochemistry and gene expression of house-fed and grazing black goats:The weight and body length of the black goats were measured,and it was found that the weight of the black goats in the house-fed group was significantly higher than that of the grazing group(P < 0.01);the body height of the black goats in the house-fed group was significantly higher than that of the grazing group(P < 0.0001);The tube circumference of the black goats in the grazing group was significantly higher than that in the house-fed group(P < 0.05).In addition,through the analysis of serum biochemical indicators and rumen fluid p H,it was found that the levels of cholesterol and low-density lipoprotein cholesterol in the black goat serum of the house-feeding group were higher,and the p H of the rumen fluid was lower than that of the grazing group(P < 0.0001).Through the study of the physiological and biochemical characteristics of the longissimus dorsi muscle of the two groups,it was found that the area of the longissimus dorsi muscle of grazing black goats was significantly smaller than that of house-fed black goats(P < 0.01),while the muscle p H value(P < 0.01),meat color(P < 0.01)and cooking loss(P < 0.05)were significantly higher than those in the house-fed group,while their electrical conductivity and crude fat were lower than those in the house-fed group(P < 0.05).In addition,the content of essential amino acids(leucine and isoleucine),unsaturated fatty acids and beneficial mineral element zinc in the muscle of grazing black goats is higher,and the content of crude fat is less,which is beneficial to human health.Through the analysis of the differentially expressed genes in the longissimus dorsi muscle of house-fed and grazing black goats,a total of 1761 significantly differentially expressed genes and 147 significantly differentially expressed lnc RNA transcripts were found.Differential genes were mainly enriched in the myogenesis and glycerophospholipid metabolism pathways.At the same time,Lnc RNA transcripts annotated a variety of target genes that play a key role in the synthesis of fatty acids and unsaturated fatty acids,The molecular mechanism underlying the difference in fatty acid metabolism between house feeding and grazing black goats was revealed.(2)Study on the difference of rumen flora between house-fed and grazing black goats:In this experiment,75 rumen fluid samples from house-fed(n=45)and grazing black goats(n=30)were collected for metagenomic sequencing,and finally 501.25 Gb Clean data was obtained.The analysis of microbial composition diversity found that the species diversity of rumen flora in the grazing group was significantly higher than that in the house-feeding group,and the composition of the rumen flora was more complex.In the composition of rumen flora,the dominant bacterial phylum in the house feeding group mainly includes Firmicutes,accounting for 83.95% of the abundance of rumen flora;and Bacteroidetes,accounting for the proportion of rumen flora abundance4.58%.The dominant bacterial phyla in the grazing group were mainly Firmicutes,Proteobacteria and Bacteroidetes,and their relative abundances accounted for 46.15%,32.10% and 5.31% of the rumen flora,respectively.Through the differential analysis of each taxonomic level,it was found that most of the differential bacteria were related to fiber degradation.The KEGG functional difference analysis of the flora confirmed that the rumen microorganisms of grazing black goats had stronger synthesis and metabolism functions of carbohydrates and proteins,indicating that the intestinal microorganisms of grazing black goats had stronger efficiency and ability to utilize rumen contents.(3)Study on the difference of rumen and serum metabolites between house-fed and grazing black goats:In this experiment,the metabolome analysis was carried out on the rumen fluid samples and serum samples of two groups of black goats by high performance liquid chromatography-mass spectrometry(UPLC-MS).A total of608 metabolites were identified in rumen fluid,and a total of 116 differential metabolites were obtained after screening by the conditions of VIP > 1,P < 0.05 and |log2FC| > 1.Fatty acids,sterols,amino acids,peptides,and nucleosides were mainly types of differential metabolites.The functions are mainly enriched in purine metabolism;biosynthesis of unsaturated fatty acids;biosynthesis of amino acids and other pathways.The significant enrichment of organic acids such as azelaic acid in the rumen of the house feeding group may lead to a decrease in the p H in the rumen,which in turn leads to the death and degradation of some microorganisms,resulting in an increase in the concentration of nucleotides in the rumen and a decrease in the diversity of rumen microorganisms.A total of 1885 metabolites were identified in serum.After screening differential metabolites using VIP > 1,P < 0.05 conditions,a total of81 differential metabolites were obtained.Differential metabolites were mainly enriched in amino acid biosynthetic pathways.The content of differential metabolites related to lipid metabolism such as betaine,methionine and choline in the grazing group was more,and the proportion of unsaturated fatty acids was higher.It was revealed that there were differences in lipid metabolism and amino acid metabolism in the body metabolism level of house feeding and grazing black goats,which laid the foundation for the subsequent research on the molecular mechanism of metabolism.In conclusion,through the preliminary analysis of multi-omics results,this study found that due to the high abundance of Butyrivibrio sp.and Ruminococcus-albus in the house feeding group,the unsaturated fatty acids in the rumen were hydrogenated to stearic acid,which in turn affected the saturated fatty acids in serum.and cholesterol and low-density lipoprotein cholesterol levels.The combined analysis with transcriptome and other results revealed the potential mechanism of the difference in lipid metabolism between house feeding and grazing black goats,which laid the foundation for subsequent exploration of the mechanism of lipid metabolism difference. |
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