GABA-enriched alfalfa silage improves milk quality and lactation hormones in dairy goats despite reduced feed intake

Gamma-aminobutyric acid (GABA) influences metabolic homeostasis, immune function, and lactation performance. Traditional exogenous GABA administration faces limitations due to intake variability and cost. A novel approach involves inoculating silage with high GABA-producing bacteria, such as Lentilactobacillus buchneri YM9, to enrich the feed with GABA and ensure more uniform dietary delivery. However, the specific effects of this silage-based GABA enrichment on ruminant performance, immunity, and overall health, particularly in dairy animals, have remained largely unexplored.

Researchers conducted a feeding trial with 36 dairy goats assigned to three total mixed ration (TMR) treatments containing alfalfa silage. The groups were: 1) CK (uninoculated control), 2) AH35 (inoculated with non-GABA-producing Lentilactobacillus buchneri AH35), and 3) YM9 (inoculated with GABA-producing Lentilactobacillus buchneri YM9). Key parameters evaluated included feed intake, lactation performance, rumen fermentation and microbiota composition, blood GABA and lactation hormones, blood cytokines and interleukins, milk GABA content, and mammary gland gene expression using qPCR.

Goats fed YM9 silage exhibited a significantly lower dry matter intake (DMI) of 1.66 kg/d compared to CK and AH35 groups, both at 1.84 kg/d. Despite reduced DMI, the YM9 group maintained milk yield comparable to CK and achieved higher yields than AH35 (P < 0.05). Notably, GABA intake, and the yield of milk fat, protein, lactose, total solids, and total nitrogen per kilogram DMI were all significantly higher in the YM9 group (P < 0.05). Milk GABA concentration was substantially greater in YM9-fed goats at 152 μmol/L, versus 114 μmol/L in CK and 111 μmol/L in AH35 (P < 0.01). Serum GABA (1.44 μmol/L), prolactin (7.65 ng/mL), and oxytocin (4.75 pg/mL) were also elevated in the YM9 group (P < 0.05). Immunoglobulin levels were generally higher in AH35, but YM9 still exceeded CK (P < 0.05), with cytokine profiles in YM9 reflecting moderate pro-inflammatory activation. Gene expression analysis revealed that 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.

YM9-fed goats achieved higher milk fat, protein, lactose, total solids, and total nitrogen per kilogram DMI, indicating improved feed efficiency and milk quality despite consuming less feed.