Using Fecal DNA Metabarcoding to Investigate Foraging Reveals the Effects of Specific Herbage on the Improved n-3 Fatty Acid (PUFA) Composition in the Longissimus Dorsi Muscle of Grazing Tan Sheep

Abstract

Understanding the natural diet of grazing sheep can help fulfill their nutritional requirements and positively affect the quality of their meat. Emerging fecal DNA (fDNA) metabarcoding technology can provide more accurate estimates for the dietary composition of free-ranging animals. This study has shown that pasture feeding can promote deposition of n-3 polyunsaturated fatty acids (PUFAs) in Tan lambs' muscle and decrease the ratio of n-6/n-3 fatty acids (FAs), and thus, we investigated the dietary composition of grazing lambs using fDNA metabarcoding to assess the prevalence of medicinal herbage plants in their diet. Herein, based on the full-time natural pasture grazing and 4-h natural pasture grazing with indoor feeding patterns, the herbage taxa (Bassia scoparia, Euphorbia humifusa, Arnebia euchroma, and Salsola sp.) most correlated to n-3 PUFAs were highlighted to elucidate how diversification in dietary components was associated with the muscle FA profile of lambs. Our findings provide experimental evidence for future feeding research.

Rumen microbial-driven metabolite from grazing lambs potentially regulates body fatty acid metabolism by lipid-related genes in liver

“…For PUFAs, the balance of n-3 PUFAs (including EPA and DHA) and n-6 PUFAs is an important index used to evaluate the nutritional value of meat quality for humans [ 45 ]. Previous studies of our team have found that grazing model increased the content of n-3 PUFAs and n-6 PUFAs and reduced the ratio of n-6/n-3 in LD muscle, which is more beneficial to human health [ 6 ]. The substantial positive association between EPA and DHA in rumen and EPA and n-3 PUFAs content in muscle indicated that the rumen of grazing lambs produced more EPA and DHA and thus potentially up-regulated the n-3 PUFAs content in muscle, contributing to better lamb meat quality.…”

“…It is well known that meat quality is strongly related to fatty acid composition, especially the proportion of PUFAs. Our previous results found that while indoor feeding increased daily gain, it enhanced the proportion of n-6/n-3 PUFAs, which negatively affected meat quality [ 6 ]. Similarly, it has been reported that the transcription of FADS2 could affect the endogenous transformation of long-chain PUFAs, reducing the bioavailability of n-3 PUFAs and promoting the accumulation of n-6 PUFAs [ 55 ].…”

“…After intramuscular fat was extracted from longissimus dorsi (LD) muscle and herbage by using a chloroform/methanol mixture, FAs in intramuscular fat were quantified using an Agilent 6890 gas chromatograph coupled with a mass spectrometer (GC/MS, Agilent Technologies Inc., Santa Clara, CA, USA). More details can be found in Guo’s research [ 6 ]. We selected the 16 lambs that underwent rumen and liver metabolism measurements, and then obtained the FAs content in their LD muscle, which are as follows: C18:2n6 (2.517 ± 0.147), C18:3n3 (0.217 ± 0.022), C20:3n6 (0.081 ± 0.005), C20:4n6 (1.054 ± 0.069), C20:5n3 (0.078 ± 0.009), C22:6n3 (0.039 ± 0.005), total FA (29.818 ± 1.654), n-3 polyunsaturated fatty acids (PUFAs) (0.334 ± 0.035), n-6 PUFAs (3.652 ± 0.208), n-6/n-3 PUFAs (12.889 ± 1.326).…”

“…The unique natural climatic conditions and high-quality grazing resources in Ningxia Hui Autonomous Region of China, have resulted in an excellent breed of Tan lamb with very good eating quality having a unique flavor, and relatively low saturated fatty acid (SFAs) and cholesterol content, and has appeared on the G20 Table in 2016. With the emergence of environmental issues and the quest for productivity, the feeding model of Tan lambs is gradually shifting to indoor feeding, with the consequent decline in lamb quality, especially in terms of FAs [ 5 , 6 ]. The current study is thus aimed at investigating the mechanisms of differences in lipid metabolism between grazing and indoor feeding sheep.…”