Effects of Asparagopsis taxiformis on enteric methane emission, rumen fermentation and lactational performance of (Norwegian Red) dairy cows

Ruminants with their rumen microbial fermentation contribute to greenhouse gas emissions when producing enteric methane. Feed supplements able to inhibit the formation of methane and thereby reduce the amount of methane emitted from rumen fermentation have been of great interest among researchers. Asparagopsis taxiformis, a red seaweed producing a diverse range of methane analogs, have recently proven its potential as a methane mitigator. The aim of this thesis was to further evaluate the potential mitigating effects of A. taxiformis supplemented to Norwegian red dairy cattle, including its possible effects on rumen fermentation parameters and lactational performance. This study confirms a dose-dependent mitigating potential of A. taxiformis, where methane production (g/day) by dairy cattle fed 0.25% A. taxiformis on an organic matter basis were significantly reduced by 22% (P = 0.037). Including A. taxiformis in the diet also affected feed palatability and significantly reduced dry matter intake (P < 0.001) and further milk yield (P < 0.001). Cows fed A. taxiformis had a significant decrease in rumen acetate-to-propionate ratio (P = 0.028) and displayed a significant (P = 0.026) increase in milk lactose contents (%). While a methane mitigating effect of Asparagopsis taxiformis was obtained, further work is required to assess possible adverse and long-term effects on animal health and productivity