Effect of addition of Ascophyllum nodosum and Asparagopsis taxiformis, alone or in combination, to an herbage-based diet on in vitro fermentation in continuous culture

Authors: ANDREEN, DANIELLE - Cornell University; Billman, Eric; BRITO, ANDRE - University Of New Hampshire; Soder, Kathy

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Brown seaweed (commonly known as kelp) is a popular, long-standing product for ruminants, and may be used in conjunction with a red seaweed that potently reduces enteric methane in cattle. However, the beneficial or negative effects of feeding these 2 species simultaneously on ruminal fermentation are unknown. When supplemented in a pasture-based diet in continuous culture, red seaweed reduced methane emissions by 99.9% but negatively impacted ruminal fermentation, both when supplemented alone or in combination with kelp. This may negatively impact animal production and should be evaluated in animal studies.

Technical Abstract: This study investigated the effect of individual or simultaneous addition of 2 macroalgae species on in vitro fermentation in continuous culture. Four single-flow continuous culture fermentors were fed an orchardgrass (Dactylis glomerata L.) herbage-based basal diet and randomly assigned to 1 of the following 4 treatments: 1) Control (CON), no macroalgae addition, 2) Ascophyllum nodosum dosed at 2.5% DM (ASC), 3) Asparagopsis taxiformis dosed at 0.5% DM (ATX), and 4) both 2.5% DM A. nodosum and 0.5% DM A. taxiformis dosed simultaneously (AS+AT). Four experimental periods were conducted in a randomized block design with 7 d of treatment adaptation and 3 d of sample collection. Fermentors were fed daily in 4 equal quantities at 0730, 1030, 1400, and 1900 h, totaling 82 g of DM/d. In the last 3 d of each experimental period, daily samples of total effluent were taken for analyses of NH3-N and VFA. One liter of effluent was collected daily (3 L total) for a composite sample that was lyophilized for analysis of DM, ash, NDF, ADF, and CP. Purines concentration of effluent and bacterial isolates was determined to estimate partitioning of N flow into feed, bacterial, and NH3-N fractions. Headspace CH4 concentration in each fermentor was measured every 15 min (96 readings/d) using a Fourier transform infrared gas analyzer, and pH was recorded every 2 min. Data were analyzed using the MIXED procedure of SAS v 9.4 with pre-planned contrasts comparing each individual macroalgae to CON (CON vs. ASC and CON vs. ATX) and comparing A. taxiformis with and without simultaneous addition of A. nodosum (ATX vs. AS+AT). Nutrient digestibility, CH4 emissions, pH, and N metabolism variables were not affected in ASC compared with CON, but total VFA concentration increased by 10%. Contrarily, the ATX treatment reduced total VFA concentration and CH4 emissions by 11 and 99.9%, respectively, compared to CON, and tended to have reduced true OM digestibility. The combination of microalgae (AS+AT) did not further reduce nutrient digestibility or total VFA concentration compared with ATX and did not change the degree of CH4 inhibition, nor affect nutrient digestibility or N metabolism variables. While the macroalgae species A. nodosum and A. taxiformis led to different fermentation patterns when added individually to continuous culture fermentors, no negative or positive interactions were observed from their simultaneous addition and their use in combination should be assessed in vivo.