Effects of GABA-enriched alfalfa silage on rumen microbiota, lactation hormones, immunity, and mammary gland gene expression, alongside lactation performance in dairy goats.

Gamma-aminobutyric acid (GABA) influences metabolic homeostasis, immune function, and lactation performance. Typically, GABA is administered exogenously, but this approach is limited by intake variability and cost. Alternatively, silage inoculated with high GABA-producing Lentilactobacillus buchneri YM9 enriches the silage with GABA and ensures more uniform dietary delivery. However, the effects of silage-based GABA enrichment and delivery on ruminant performance, immunity, and health remain unclear. Hence, we conducted a feeding trial with 36 dairy goats assigned to three TMR treatments containing alfalfa silage: 1) CK (uninoculated control), 2) AH35 (inoculated with non-GABA-producing Lent. buchneri AH35), and 3) YM9 (inoculated with GABA-producing Lent. buchneri YM9). Feed intake and lactation performance, rumen fermentation and microbiota, blood GABA and lactation hormones, blood cytokines and interleukins as well as milk GABA and mammary gland gene expression were evaluated. YM9-fed goats had lower DMI (1.66 kg/d) compared with CK (1.84 kg/d) and AH35 (1.84 kg/d) but maintained milk yield comparable to CK and higher than AH35 (P < 0.05). GABA intake, and milk yield, fat, protein, lactose, total solids, and total nitrogen per kilogram DMI were higher in YM9 (P < 0.05). Milk GABA was greater in YM9 (152 μmol/L) than CK (114 μmol/L) and AH35 (111 μmol/L) (P < 0.01). Serum GABA (1.44 μmol/L), prolactin (7.65 ng/mL), and oxytocin (4.75 pg/mL) were elevated in YM9 (P < 0.05). Immunoglobulins were higher in AH35 overall, but YM9 exceeded CK (P < 0.05), with cytokine profiles in the YM9 group reflecting moderate pro-inflammatory activation. YM9 upregulated GSR and downregulated NOX4, TNF, and IFNG (P < 0.05). Microbiota analysis showed comparable alpha diversity between YM9 and CK with Prevotella dominance in the YM9 group, and significant correlations among GABA, microbial taxa, hormones, and mammary gland genes. Feeding dairy goats with GABA-enriched silage was associated with improved feed and lactation efficiency. It also enhanced lactation hormones, immune responses, and expression of antioxidant-related gene alongside reduced inflammatory related genes. These findings provide alternative approach for dietary GABA delivery to ruminants for enhanced productivity and health, although further studies are required to verify the mechanisms.