Abstract
Enteric methane (CH4) emissions from ruminants contribute significantly to global greenhouse gas inventories. This study evaluated the effects of dietary supplementation with the red seaweed Asparagopsis taxiformis (AT) on enteric methane emissions, rumen fermentation kinetics, milk yield, and milk composition in lactating Holstein dairy cows. Twelve multiparous lactating Holstein cows were assigned to a 3 x 3 replicated Latin square design with three treatments: control (0% AT), low-dose AT (0.25% of organic matter intake, OMI), and high-dose AT (0.50% OMI). Supplementation with AT at 0.50% OMI reduced daily enteric methane production by up to 58.4% (P < 0.01) without adversely affecting dry matter intake (DMI) or milk yield. Total volatile fatty acid (VFA) concentrations in the rumen were unaltered, but the acetate-to-propionate ratio decreased from 3.12 in the control group to 2.21 in the 0.50% AT group (P < 0.05). Milk composition (fat, protein, lactose) remained stable, although an increase in milk iodine and trace bromoform concentrations was detected at the high dose. These findings demonstrate that low-level dietary inclusion of Asparagopsis taxiformis represents a highly effective nutritional strategy to mitigate methane emissions from dairy operations while maintaining animal performance.
