Effects of different Lactobacillus plantarum strains supplementation on milk performance, rumen fermentation, and microbiota in dairy cows

This study combined in vitro and in vivo experiments to evaluate the effects of three Lactobacillus plantarum strains (AP 6-5, 18-5-5, and Y2-2-3) on rumen fermentation, microbiota composition, and productive performance in lactating Holstein cows. In the in vitro trial, rumen fluid from three fistulated cows was incubated with TMR substrate supplemented with each strain (1 × 10 7 CFU/mL) at 39 °C for 24 h. Compared with the CON, strains AP 6-5 and 18-5-5 reduced ruminal lactate and acetate concentrations, and strain 18-5-5 further decreased microbial crude protein (MCP). In the in vivo trial, forty-four cows were randomly assigned to four groups: a control (CON) and three treatment groups receiving 5 × 10 10 CFU/d of strains AP 6-5 (AJT), 18-5-5 (NM), or Y2-2-3 (LP42) for 28 days after a 7-day adaptation. The NM group showed the highest DMI, milk yield, and lactose content, while the LP42 group had higher valeric acid concentration and fecal pH. Rumen microbiota analysis indicated enrichment of pathways related to carbohydrate utilization (NM) and protein metabolism (LP42). Overall, supplementation with L. plantarum , particularly strain 18-5-5, improved nutrient intake, milk production, and rumen microbial function in lactating cows.