Feeding a cultivated seaweed-based additive to dairy cows: Effects on enteric methane emissions, milk production, and milk safety.

Sixteen multiparous lactating Holstein cows were used in a randomized complete block design to evaluate the effects of dietary supplementation with a cultivated seaweed-based additive (Synergraze Inc., Calgary, AB, Canada) on feed intake, enteric CH4 emissions, feed efficiency, and lactational performance. The experimental period consisted of a 5-wk treatment period preceded by a 2-wk covariate (pretreatment) period. At the start of the experiment, cows were blocked (8 blocks; 2 cows/block) based on milk yield and DIM, and subsequently adjusted using pretreatment milk yield and enteric CH4 emissions. Within each block, cows were randomly assigned to 1 of 2 dietary treatments: (1) a TMR (63:37 forage:concentrate ratio) without supplementation (control, CTL), or (2) the same TMR supplemented with 0.25% (DM basis) of the seaweed additive (SEA). Cows were fed ad libitum to allow 5% orts (as-fed basis). The SEA supplement was hand-mixed with a portion of the TMR and a commercial protein supplement and offered as a premix before delivery of the diet to ensure complete consumption. Across the experiment, CHBr3 concentration in SEA averaged 4.61 ± 0.187 mg/g DM. Supplementation with SEA markedly reduced enteric CH4 production (g/d) by 45.9%, CH4 yield (g/kg of DMI) by 44.8%, and CH4 emission intensity (g/kg of ECM) by 47.2% compared with CTL. Dry matter intake decreased by 1.5 kg/d (5.62%) with SEA supplementation. Milk yield, 4% FCM, and ECM were not affected by treatment. Milk fat and lactose concentrations were similar between treatments; however, milk protein concentration increased with SEA supplementation. Yields of milk components, MUN concentration, and SCC were not affected by treatment. Feed efficiency, BW, and BCS were also unaffected by SEA supplementation. Bromoform was not detected in milk from SEA-fed cows, and milk iodine and bromide concentrations remained below reported health-based reference values. Results of this study demonstrate the strong potential of SEA to mitigate enteric CH4 emissions (production, yield, and intensity) without negatively affecting animal performance or compromising milk safety.