Age-dependent gut microbiota associated with intramuscular fat deposition in Longdong cashmere goats

Intramuscular fat (IMF) is a key determinant of meat quality, influencing tenderness, juiciness, and flavor. Previous studies have reported that the deposition of IMF is controlled by various factors. However, there is a shortage of research exploring the variations in IMF deposition across age groups from a microbial perspective. This study evaluated the differences in IMF deposition between yearling (1-year-old) and mature (4-year-old) Longdong Cashmere goats and analyzed its association with gut microbiota. The results revealed that the IMF content in shoulder meat and blood lipid levels increased with age (p < 0.05). Conversely, the contents of lipoprotein lipase (LPL) in the liver and duodenum significantly decreased with age. Microbial diversity differed between the two age groups, with specific microbiota identified from the gut of goats involved in the lipid metabolism pathway. The concentrations of valeric and isovaleric acids in the rumen, as well as acetic, propionic and isovaleric acids in the colon, were higher in yearling goats than in mature goats (p < 0.05). Spearman correlation analysis of IMF deposition indicators with gut microbiota revealed that, within the rumen, the abundances of CAG-791 and Sodaliphilus were positively correlated with IMF content in shoulder meat and TG levels, while exhibiting a negative correlation with the contents of valeric acids. Furthermore, the abundance of Clostridium_R showed a positive association with IMF content in shoulder meat and with the abundances of CAG-791and Sodaliphilus. In contrast, the abundance of Bact_11 was negatively correlated with IMF content in shoulder meat, TG levels, and the abundances of CAG-791, Sodaliphilus and Clostridium_R. Within the abomasum, the abundances of UMGS and Hylemonella_582308 were correlated with IMF content in the shoulder meat, as well as serum LDL and VLDL levels. This study provides significant insights into the age-dependent gut microbiota associated with intramuscular fat deposition in goats and identifies several potential gut microbiota for further research on their impacts on IMF deposition.