Supplementation of Oilseeds to an Herbage Diet High in Condensed Tannins Affects Methane Production with Minimal Impact on Ruminal Fermentation in Continuous Culture

Authors: Billman, Eric; ROCA-FERNANDEZ, ANA - Universidad De Santiago De Compostela; DILLARD, LEANNE - University Of Auburn; Soder, Kathy

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2022
Publication Date: 3/3/2022
Citation: Billman, E.D., Roca-Fernandez, A.I., Dillard, L., Soder, K.J. 2022. Supplementation of Oilseeds to an Herbage Diet High in Condensed Tannins Affects Methane Production with Minimal Impact on Ruminal Fermentation in Continuous Culture. Journal of Animal Science. 8(3):109. https://doi.org/10.3390/fermentation8030109.
DOI: https://doi.org/10.3390/fermentation8030109

Interpretive Summary: Compounds in plants, such as condensed tannins, may reduce methane production in cattle, but have negative impacts on ruminal fermentation. Supplementation of diets high in tannins with oilseeds may maintain fermentation while further reducing methane. We evaluated three oilseeds (soybean, sunflower and canola) plus a combination of the three oilseeds to evaluate effects on ruminal fermentation and methane production in a continuous culture fermentor system. Addition of canola, sunflower and the mix of the three oilseeds reduced methane more than soybean, without decreasing nutrient digestibility. The addition of canola and sunflower seed meal to forages high in condensed tannins may provide excellent reductions in daily methane emissions, while maintaining desirable feed digestibility in ruminant livestock.

Technical Abstract: Condensed tannins (CT) have been observed to reduce enteric methane (CH4) production when added to ruminant diets. However, high concentrations of CT in forages such as sericea lespedeza [SL; Lespedeza cuneata (Dum. Cours.) G. Don] may depress nutrient digestibility. Oilseed crops, high in lipid concentration, have also been found to reduce enteric CH4 through toxicity to methanogenic bacteria without depressing nutrient digestibility. This study used an in vitro continuous-culture ruminal fermentation to determine if the addition of seed meal from several oilseed crop species would improve nutrient digestibility of high-CT diets while further reducing enteric CH4 production. The experimental design was a 4 × 4 Latin square, with 4 diets (45% orchardgrass; Dactylis glomerata L.), 45% SL, 10% oilseed meal) using canola (CAN; Brassica napus L.), soybean (SOY; Glycine max L.), sunflower (SUN; Helianthus annuus L.), and a mix of all three species (MIX; equal proportions) over four, 10-d periods. Fermentors were fed 82 g of dry matter/d in 4 equal feedings. Methane was recorded every 10 mins, and effluent samples were analyzed for pH, volatile fatty acids, dry matter, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber to determine apparent and true digestibilities. Nitrogen (N) flows and purines were also measured to calculate bacterial N efficiency. The CAN, SUN, and MIX diets had greater concentrations of ether extract (7 – 8 g/kg) than the SOY diet (5.7 g/kg), which contributed to the greater (P < 0.001) reduction in enteric CH4 production in those diets (13 – 30 mg/d) compared to the SOY diet (84 mg/d). Apparent and true nutrient digestibilities were not affected (P > 0.05) by the addition of oilseed meal. While N intake increased (P < 0.001) concomitant with crude protein increases in the diets, there were no additional effects on bacterial N metabolism or flows. These results indicated that CAN and mixes containing CAN were most effective at reducing enteric CH4 emission while not decreasing nutrient digestibility. Supplementing high-CT herbage diets with CAN and SUN in vitro resulted in reduced CH4 output without negatively impacting nutrient digestibility. Further research is needed in vivo to evaluate whether these results translate to greater feed efficiency or animal production.