180 - Effects of Forage Mixtures on Rumen Fermentation Parameters as Assessed by Continuous Culture

The impact of using diverse forage mixtures on rumen performance is poorly characterized. The objective of this study was to evaluate the impact of feeding diverse pastures on rumen performance using in vitro continuous culture fermenters. Treatments were assessed using a 4 x 4 Latin square design. Each 10-d period included 7-d of adaption followed by 3-d of sample collection. Dietary treatments (DM basis) included 1) 50% orchardgrass + 50% alfalfa (OG-ALF); 2) 50% OG-ALF + 50% red clover (RC); 3) 50% OG-ALF + 50% pearl millet (MIL); and 4) 50% OG-ALF + 50% sorghum x sudangrass (SUD). Forage diets (131 g DM/ fermenter/ d) were divided into 4 portions/d (33%, 0600 h; 17%, 0720 h; 33%,1800 h; 17%, 1920 h). Fermenter pH measurements were collected every min for the entire experiment. Methane concentrations were measured using a gas probe and recorded twice daily (0530 h,1730 h) in triplicate on d 7, 8, 9, and 10. Daily total effluent samples were collected on d 8, 9, and 10 for VFA analysis. Results were analyzed using PROC MIXED of SAS. There were no differences in total VFA concentrations (P = 0.08), molar proportions (P = 0.22), or individual VFA ratios (P > 0.05) as a result of treatment. Fermenter pH did not differ between fermenters as a result of treatment (P > 0.05). Fermenters receiving OG-ALF had the greatest methane concentration (50.8 mg/dL), which was higher (P < 0.05) than methane concentrations in fermenters receiving MIL (6.2 mg/dL), SUD (6.9 mg/dL), or RC (21.2 mg/dL). Methane concentrations from the MIL, SUD and RC treatments did not differ (P > 0.05). This indicates that binary forage mixtures may have lower nutritional value compared with diverse mixtures, and this diversification could provide nutritional benefits.