Bacterial direct-fed microbials fail to reduce methane emissions in primiparous lactating dairy cows

Area of Science:

• Animal Science
• Microbiology
• Environmental Science

Background:

• Direct-fed microbials (DFM) are explored for enhancing animal productivity and reducing environmental impact.
• Previous research suggests DFM can mitigate methane (CH4) emissions, but responses vary with diet.
• The efficacy of specific bacterial DFM in dairy cows under different dietary conditions requires further investigation.

Purpose of the Study:

• To evaluate the effect of three bacterial DFM on methane emissions, ruminal fermentation, and milk production in primiparous dairy cows.
• To assess DFM efficacy on contrasting high-starch and high-fiber diets.
• To determine if in vitro methane-reducing effects translate to in vivo performance in dairy cows.

Main Methods:

• Eight primiparous dairy cows were assigned to high-starch (HSD) or high-fiber (HFD) diets in a 4x4 Latin square design.
• Treatments included a control and three DFM: Propionibacterium freudenreichii 53-W, Lactobacillus pentosus D31, and Lactobacillus bulgaricus D1.
• Methane emissions were measured using respiration chambers; ruminal fermentation, microbial populations, milk composition, and body weight were also analyzed.

Main Results:

• No DFM treatment significantly reduced enteric methane emissions in dairy cows, irrespective of diet.
• Propionibacterium freudenreichii 53-W increased methane intensity by 27% in cows fed the HSD.
• DFM did not affect ruminal fermentation parameters, microbial populations, or milk fatty acid composition; however, some DFM tended to increase body weight gain on HSD.

Conclusions:

• Bacterial DFM, including P. freudenreichii, L. pentosus, and L. bulgaricus, did not reduce methane emissions in lactating dairy cows.
• The tested DFM failed to modulate ruminal fermentation, contrary to in vitro findings.
• Diet composition did not alter the lack of methane mitigation by these specific DFM in dairy cows.