Effects of by-product feed inclusion in a grass hay-based diet on nutrient disappearance, total gas and methane production, rumen fermentation and protozoal populations in an artificial rumen (RUSITEC)

Context Dietary manipulation can reduce enteric methane in beef cattle but limited options exist for perennial forage-based diets. Aims An artificial rumen system (RUSITEC) was used to assess the effects of including quinoa screenings, flax screenings, and sunflower screenings in a grass hay-based diet on nutrient disappearance, total gas production (GP), methane (CH4) production, ruminal fermentation, and protozoa populations. Methods The experiment was a randomized complete block design with four treatments assigned to 16 fermenters (n = 4 per treatment) in two RUSITEC apparatuses. The control diet was timothy grass hay only, with by-product treatments of grass hay plus quinoa screenings, flax screenings, or sunflower screenings, at inclusion rates of 21.4%, 11.2%, and 12.3% diet DM, respectively. The study duration was 15 days, with an 8-day adaptation period followed by a 7-day sample collection period. Data were analyzed using PROC MIXED in SAS with fixed effects of treatment, day of sampling (repeated measure), and their interaction and with RUSITEC and fermenter as random effects. Key results Compared to the control, the inclusion of quinoa and flax had no effect (P > 0.05) on dry matter (DMD) or organic matter disappearance; however, these were lower (P < 0.001) than sunflower. Sunflower and quinoa did not affect (P > 0.05) rumen fluid propionate production compared to the control; however, propionate production was increased (P < 0.05) with flax. Additionally, sunflower decreased (P = 0.044) rumen fluid acetate production as compared to the control, quinoa and flax groups. Sunflower, compared to the control, had fewer (P < 0.05) protozoa. There was no effect (P > 0.05) of by-products on GP (L day−1). Sunflower reduced (P < 0.05) CH4 by 42% (mg g−1) DM incubated and 31% (mg g−1) DMD, whereas quinoa and flax had similar CH4 production to the control. Conclusions This study suggested sunflower screenings have the potential to decrease CH4 when included in a grass hay-based diet. Implications Methane reduction was accompanied by reduced DMD, therefore, animal performance may be negatively impacted. Although quinoa and flax did not reduce CH4 production, they demonstrated potential to supplement hay-based diets without decreasing DMD.