Dual-flow continuous culture fermenters were used to evaluate the impacts of forage mixtures on ruminal fermentation. Diets (DM basis) contained 40% red clover combined with 1) 60% orchardgrass (OG); 2) 30% orchardgrass + 30% meadow fescue (MF); 3) 20% orchardgrass + 20% meadow fescue + 20% Kentucky bluegrass (KYBG); or 4) 15% orchardgrass + 15% meadow fescue + 15% Kentucky bluegrass + 15% perennial ryegrass (PRG). Treatments were randomly assigned to fermenters in a 4 x 4 Latin square design. Each 10-d period included a 7-d adaptation and 3-d sampling period. Diets (110 g DM/d) were added across 4 feedings/d (33% each, 0700 h and 1600 h; 17% each, 0820h and 1720 h). Fermenter pH was recorded continuously for 10-d. Methane was measured on d 7-10 at 0630 and 1530 h. Effluent samples were collected on d 8-10. Results were analyzed using PROC GLIMMIX of SAS with significance at P ≤ 0.05. Apparent digestibility of DM, OM, NDF, and ADF was greatest (P ≤ 0.05) for fermenters receiving KYBG, followed by PRG. Apparent DM and OM digestibility for OG and MF were less than KYBG by 18.0% and 19.6%, respectively. Fermenters receiving KYBG spent the greatest amount of time under pH 5.8 (avg. 15.5 h/d; P = 0.0004). Acetate:propionate and acetate + butyrate:propionate ratios were greater for fermenters receiving KYBG (4.09 and 4.71) and PRG (4.03 and 4.65; P < 0.0001). Water soluble carbohydrate concentration of effluent was least for KYBG (0.80 mg/ mL; P ≤ 0.05). Methane output for KYBG (116.8 mg/dL; P < 0.0001) was greater than that of OG (13.7 mg/dL), MF (31.7 mg/dL), and PRG (11.9 mg/dL) which did not differ from one another. These results suggest that diets containing KYBG and PRG were more digestible with PRG having the added benefit of decreased methane output.

The aim of this study was to evaluate the effects of processed dietary supplements derived from two seaweeds, Saccharina latissima (SL) and Ascophyllum nodosum (AN), on microbial methane production and fermentation profile using in vitro methods. Four dual-flow continuous culture fermenters were utilized in a 4x4 Latin Square design to assess these 4 supplements: unwashed, coarsely milled SL (UNW), 3-min rinsed SL (3MR), 20-sec blanched SL (20SB), and a crude phlorotannin extract from AN (PHLT). Treatments were randomly assigned to fermenters and were top dressed on the total mixed ration (TMR) at 5% of total dry matter (DM). Four, 10-d experimental periods were conducted, consisting of a 7-d equilibration period followed by a 3-d sampling period. Vessel pH was continually measured, and effluent samples were collected for volatile fatty acid (VFA) analysis and calculation of DM, organic matter (OM), neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibilities. Methane was measured prior to the first AM and PM feedings during the 3-d sampling period. Data were analyzed using the PROC MIXED procedure of SAS (9.4) with fermenter as the random effect and period and treatment as fixed effects. Processed treatments (3MR= 7.86, 20SB= 5.75, PHLT= 10.46 mg/dL) yielded less methane (P < 0.02) than unprocessed (UNW= 24.06 mg/dL). Apparent digestibilities of DM, OM, NDF and ADF were not affected by treatment. Total VFA (mM) was greater (P = 0.02) in 3MR than PHLT. The acetate to propionate ratio (A:P) was greater (P < 0.01) in PHLT compared with 20SB, 3MR and UNW (5.62 vs 1.47, 1.27 and 1.54, respectively). Time spent below pH 5.8 during fermentation was not affected by treatment. These results indicate that seaweed processing method can affect methane production in vitro without negatively impacting rumen fermentation and should be further investigated using in vivo models.