Impact of a native rumen microbe supplement provided in feed on production performance and enteric methane emissions in lactating dairy cows

The objective of this randomized controlled study was to evaluate the effects of a native rumen microbial feed supplement on production performance (milk production, milk composition, and feed efficiency). Additionally, the effects of the microbial supplement on enteric methane emissions were assessed. Forty-six second-, third-, and fourth-parity Jersey cows at 59 ± 8 DIM were blocked by baseline milk yield and randomly assigned to control (no microbial supplementation) or treatment (GF-MFS; TMR containing 5 g/cow per day of a native rumen microbial feed supplement containing a minimum of Clostridium beijerinckii at 2 × 10⁶ cfu/g, Pichia kudriavzevii at 2 × 10⁷ cfu/g, Ruminococcus bovis at 2 × 10⁷ cfu/g, and Butyrivibrio fibrisolvens at 2 × 10⁷ cfu/g). Cows were housed in a single group and fed the study diets ad libitum for 16 wk. Individual milk yield was recorded using electronic milk meters, and milk fat and protein were measured using optical in-line analyzers at each of 2 daily milkings. Individual cow TMR intake was recorded through the Biocontrol CRFI feed intake control and measurement system. Enteric methane emissions were measured using GreenFeed units. Somatic cell count was determined in milk composite samples collected at 2 consecutive milkings on a weekly basis. Treatment and treatment by time effects were assessed by multiple linear regression. Overall treatment effects were observed for ECM, milk, and fat yields; yields were (mean ± SEM) 2.19 ± 0.90, 1.64 ± 0.74, and 0.10 ± 0.03 kg/d higher for GF-MFS compared with control cows, respectively. There was also a tendency for higher milk protein yield in GF-MFS cows. No overall treatment effects were observed for milk fat and protein concentrations and DMI. Furthermore, positive treatment effects were observed on feed efficiency (0.09 ± 0.04 units higher for GF-MFS cows) and log₁₀ SCC (0.13 ± 0.06 units lower for GF-MFS cows). Methane intensity tended to be lower for GF-MFS compared with control cows, but methane production and yield were similar for GF-MFS and control cows. In conclusion, the supplementation of native rumen microbes effectively improved economically important outcomes such as ECM, milk and fat yields, feed efficiency, and lowered SCC. Larger studies are required to assess the effect of the evaluated native rumen microbial feed supplement on enteric methane emissions.