Lactobacillus spp. supplementation under grazing conditions: Methane and milk production responses during early lactation

) tracer technique. Data were analyzed using a completely randomized design based ANCOVA. Methane production (g/day), yield (g/kg DMI) and intensity (g/kg energy corrected milk) were not affected by the inclusion of either form of Lactobacillus spp. in the diet, although a numerical reduction of 6% in methane yield was observed in the FLA group, compared with the control group. Methane emissions from the CON cows were approximately 38% lower than those estimated using inventory factors. This is likely due to the low fiber concentration and low DM concentration of the PRG offered likely resulting in a high ruminal passage rate, reducing ruminal retention time and extent of fermentation. The high passage rate could have also restricted the colonization potential of supplemented Lactobacillus spp. This, combined with the large rumen volume of dairy cows and low dose rate may in part explain the limited methane mitigation. Notably, production responses to Lactobacillus spp. supplementation have been more evident in small ruminants, suggesting species-specific differences. These findings highlight the need for tailored probiotic strategies, particularly in pasture based dairy systems.