Abstract

Objectives: We investigated the effect of different incorporations of Acacia mearnsii forage (AM) in maize silage or A. mearnsii tannin extract (AME) in pellets on dairy rumen CH₄.
Materials and Methods: Using a completely randomized design per experiment, 24 crossbred Holstein–Friesian and Jersey dairy cows per experiment were divided into groups (n = 6 cows per experiment). Dairy cows were fed pellets with 0% (0PEL), 0.75% (0.75PEL), 1.5% (1.5PEL), or 3.0% (3PEL) of AME (Experiment 1). Furthermore, dairy cows were fed 0% (0AM), 5% (5AM), 15% (15AM), or 25% (25AM) of AM in maize silage (Experiment 2). Data sampling period (21 days) of ruminal CH₄ and nitrogen (N₂), carbon dioxide (CO₂), and hydrogen (H₂) gases (% vol) was conducted after the adaptation period (14 days) for each experiment.
Results: Enteric CH₄ was not affected by AME inclusion, but AM inclusions affected CH₄, except for CH₄ (% vol per cow per day). The inclusions of 25AM decreased CH₄ per nutrient intake (kg/day), such as dry matter (DM), organic matter (OM), crude protein, acid detergent fiber (ADF), and neutral detergent fiber (NDF). In addition, there was a linear and quadratic AM inclusion effect on CH₄ per intake of nutrients, including DM, NDF, ADF, and OM.
Conclusion: Enteric CH₄ was not affected by AME but was decreased by AM in dairy cows.

Key words: Greenhouse gas; tannins; rumen– headspace gases; Acacia mearnsii; CH₄.