Variation in Gut Microbiome Enables Intramuscular Fat Deposition Difference Between Sheep and Goat

Intramuscular fat (IMF) is one of the key factors affecting the quality of livestock meat, as it is closely related to muscle color, tenderness, juiciness, water-holding capacity and flavor. The IMF deposition is impacted complexly by various factors, including animal breeds, age, feed, and mi-crobiota. Currently, there is a shortage of research exploring the similarities and differences in IMF deposition between goats and sheep from a microbial perspective. Thus, we selected Longdong cashmere goats (n=10) and Tan sheep (n=10) as the subjects of our research, both of which are recognized for their exceptional meat quality traits. Their differences were assessed including the dressing percentage, GR values, IMF content of muscles, lipid levels, FAS and HSL content of di-gestive glands and gut contents, SCFAs content and microbial diversity in the rumen, abomasum and colon. Spearman correlation analysis was conducted to further analyze the relationship be-tween fat deposition, physiological indicators and microbiota. The results showed that the shoul-der and rump IMF content of Longdong cashmere goats was significantly higher than that of Tan sheep (p< 0.05). The overall levels of triglycerides (TG), total cholesterol (TC), free fatty acids, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and very low-density lipoprotein cholesterol (VLDL-C) in goats were notably higher than those found in sheep. (p< 0.05). The content of FASin the duodenum of goats showed a significant decrease (p=0.04), while the content of HSL in both the pancreas (p= 0.04) and duodenum (p< 0.001) exhib-ited a significant increase. The content of FAS, pH values, content of acetic acid, propionic acid, valeric acid and isovaleric acid in colonic chyme of goats were significantly decreased than those of sheep. The HSL content of goat abomasal chyme showed a significant increase (p= 0.004), while the content of acetic acid and propionic acid demonstrated a significant decrease in comparison with those of sheep (p< 0.05). The Chao1 and β diversity in the abomasum and colon varied be-tween Longdong cashmere goats and Tan sheep. Spearman correlation analysis showed that Sele-nomonas_A, Bifidobacterium_388775 and Eubacterium_Q in the abomasum were directly correlated with the shoulder and rump IMF content (|r|> 0.45). UBA5905 and GCA-900066495 in the colon were negatively correlated with the content of acetic acid, propionic acid and isovaleric acid, and positively correlated with shoulder IMF content. This study emphasizes the importance of aboma-sum and colon microbes in IMF deposition in mutton, and offers available strategies to enhance meat quality and its market value.