Dietary supplementation of lamiaceae aromatic oils: effects on performance, rumen fermentation, and ruminal...

This study investigated the effects of sage (Salvia officinalis), thyme (Thymus sp.), and lavender (Lavandula angustifolia) aromatic oils on growth performance, rumen fermentation, and microbial composition in Holstein calves. A total of 32 calves were randomly assigned to four groups: a control group (CONT) receiving unsupplemented milk and three experimental groups supplemented with 150 µL/day/calf of sage (SAG), thyme (THY), or lavender (LAV) aromatic oil, along with starter feed and forage. Sage (4.89 and 10.14%, respectively) and lavender (6.75 and 20.29%, respectively) oils significantly improved body weight and average daily weight gain at weaning, while all aromatic oils enhanced feedstuff dry matter (DM) intake (P < 0.05). Rumen ammonia nitrogen levels remained unaffected by sage and lavender oils but increased with thyme oil supplementation (P < 0.05). Sage oil increased the molar concentrations of acetic, iso-valeric, total (short chain fatty acids) SCFA (P < 0.01), straight SCFA (P < 0.01), and branched SCFA (P < 0.05). Both sage and lavender oils elevated propionic (P < 0.05) and butyric acid levels (P < 0.001). In terms of rumen microbiota, thyme oil increased the abundance of Bifidobacteriaceae by approximately 73% (P < 0.05), while sage oil significantly increased the relative proportion of Acidaminococcaceae by approximately 160% (P < 0.001). Sage and lavender oils reduced Prevotellaceae but increased Lachnospiraceae (P < 0.001). In conclusion, supplementation with 150 µL/day of sage, thyme, or lavender aromatic oils improved feedstuff DM intake, rumen fermentation, and microbial populations in Holstein calves. Sage and lavender oils showed the most pronounced benefits by increasing SCFA production and promoting potentially beneficial bacterial families such as Lachnospiraceae and Acidaminococcaceae, which are associated with enhanced carbohydrate fermentation and rumen development, while reducing Prevotellaceae abundance. Thyme oil increased Bifidobacteriaceae, suggesting a positive modulation of gut microbial balance. These findings indicate that aromatic oils, particularly sage and lavender, may support healthier rumen maturation and improved calf performance during early-life feeding.