Effects of Brown Seaweed ( Ascophyllum nodosum ) Supplementation on Enteric Methane Emissions, Metabolic Status and Milk Composition in Peak-Lactating Holstein Cows.

The dairy industry contributes significantly to anthropogenic methane emissions, which have an impact on global warming. This study aimed to investigate the effects of a dietary inclusion of brown seaweed Ascophyllum nodosum on enteric methane emissions (EMEs), hematological and blood biochemical profiles, and milk composition in dairy cows. Eighteen Holstein cows were divided into three groups: CON (non-supplemented cows), BS 50 (50 mL of 10% A. nodosum ), and BS 100 (100 mL of 10% A. nodosum ). In each cow, measurements of EME, dry matter intake (DMI), and milk yield (MY), as well as blood and milk sampling with respective analyzes, were performed before supplementation (P1), after 15 (P2) days, and after 30 (P3) days of supplementation. A. nodosum reduced ( p < 0.05) methane production, methane yield, and methane intensity in both BS 50 and BS 100 , and raised DMI ( p < 0.05) only in BS 50 . Total bilirubin ( p < 0.05) was higher in BS 50 compared to CON cows in P2, and triacylglycerols were lower ( p < 0.05) in BS 50 than in CON cows in P3. Higher milk fat content was found in BS 50 than in CON cows in P3. C16:0 proportions were higher ( p < 0.05) in BS 50 and BS 100 than in CON cows, while C18:3n-3 was higher ( p < 0.05) in BS 100 than in BS 50 and CON cows in P3. Dietary treatment with A. nodosum reduced EMEs and showed the potential to increase DMI and to improve energy status as well as milk composition in peak-lactating dairy cows.