Effects of Red Seaweed on Milk Production and Methane Emissions

Enteric fermentation by ruminants is the largest source of methane emissions in the US (approximately 25% of total methane emissions), corresponding to approximately 2.7% of human activity greenhouse gas emissions. Improving feed efficiency is likely the most effective methane mitigation strategy at the global scale. Recently, algae-based feeds have gained attention because they may be able to not only suppress methane emissions, but also to improve animal feed efficiency. Our objective was to evaluate how incremental increases of the seaweed Chondrus crispus affects milk and methane production in organic dairy cows.

There is growing interest in feeding seaweeds to dairy cows because of their effects on methane suppression (Machado et al., 2014) while improving animal health (Antaya et al., 2015). The red seaweed species Asparagopsis taxiformis showed up to a 99% reduction in methane emissions (Machado et al., 2014; Kebreab et al., 2019). However, this seaweed species does not grow in colder climates, has been shown to be highly invasive and to produce poor biomass.

Brown seaweed (i.e., kelp meal) is widely available and commonly fed in organic dairies across the US (Hardie et al., 2015; Antaya et al., 2015). However, feeding kelp meal to organic dairy cows during the grazing season had minor effects on suppressing methane emissions. The red seaweed Chondrus crispus is available locally and research showed that small amounts (i.e., 0.5% of the diet dry matter) of this species reduced methane emissions by over 12%.

Research was conducted at the UNH Organic Dairy Research Farm where 18 mid-lactation organic certified Jersey cows were used in a replicated Latin square design. Cows were blocked by parity and days in milk and, within block, randomly assigned to diet sequences. Cows were fed diets containing (dry matter basis) 0, 3 or 6% Chondrus crispus. Each experimental period last 24 days, with 14 days for diets adaptation and 10 days for data and sample collection (total = 72 days). Diets were fed as total mixed rations, with the control treatment (0% Chondrus crispus) consisting of (dry matter basis) 65% grass-legume baleage and 35% concentrate mix; baleage was replaced with 3 or 6% C. crispus in the remaining 2 diets. Diets averaged 16% crude protein, 35% neutral detergent fiber, and 19% starch (dry matter basis).

Dry matter intake decreased linearly and quadratically in cows fed incremental amounts of red seaweed (Table 1). However, production of milk, 4% fat-corrected milk, and energy-corrected milk were not affected by diets. Decreased dry matter intake without a change in the production of energy-corrected milk resulted in a tendency to improve feed efficiency linearly with feeding increasing levels of the seaweed. We observed no effects of diets in the percentage and production of milk fat and protein. In contrast, milk urea nitrogen responded quadratically by decreasing from 12.2 to 11.1 mg/ dL when comparing the control diet (0% seaweed) with the 3% Chondrus diet and went back up to 12.2 mg/ dL in cows receiving 6% Chondrus. It is not clear why this quadratic response was observed.

Enteric methane production decreased linearly from 383 to 351 g/d in cows fed incremental amounts of seaweed. This 8.4% reduction was likely caused by the observed decrease in dry matter intake due to a positive correlation between feed intake and methane emissions. Contrarily, methane yield and intensity were not affected by differential seaweed diets.

This material is based upon work supported by the NH Agricultural Experiment Station, through joint funding of the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 1017808, and the state of New Hampshire. Authors include D. Reyes, J. Sacramento, Y. Geng, L. Silva, N. Price. C. Quigley, and A.F. Brito