Effects of Dietary Glycerol Fatty Acid Esters on Growth and Nutrient Digestion in Hu sheep: Insights from Jejunum Transcriptome and Microbiome Analysis

This study evaluated the effects of dietary glycerol fatty acid esters (GFAs) on growth performance, nutrient digestibility, nitrogen metabolism, jejunal microbiota, and intestinal transcriptome in Hu sheep. Thirty-six 4–5-month-old male Hu sheep were randomly assigned to three groups receiving a basal diet (GFA0%) or diets supplemented with 0.15% (GFA0.15%) or 0.20% (GFA0.20%) GFA for 52 days following a 7-day adaptation period. Growth performance parameters were unaffected (p > 0.05); however, feed-to-gain ratio decreased linearly and quadratically with increasing GFA levels (p < 0.001). GFA supplementation improved ether extract (EE) and neutral detergent fiber (NDF) digestibility (p < 0.05), neutral detergent fiber ADF digestibility showed a linear increase(linear = 0.025), significantly reduced fecal and urinary nitrogen excretion, and enhanced nitrogen utilization (p < 0.05). Jejunal microbiota analysis revealed significant genus-level separation among groups, with increased Bacillota abundance and the enrichment of Acetitomaculum and [Ruminococcus]_gauvreauii_group in the GFA0.20% group. Functional prediction indicated enhanced fiber degradation, nitrogen metabolism, and host interaction functions. Transcriptomic analysis showed dose-dependent gene regulation, with GFA0.15% primarily enriching immune-related pathways, while GFA0.20% additionally activated lipid and steroid metabolism pathways. Integrated microbiome-host analyses demonstrated coordinated regulation of nutrient metabolism and immune responses. Overall, dietary inclusion of 0.20% GFAs optimized feed efficiency, nutrient utilization, and intestinal metabolic-immune function in Hu sheep.