title: Effects of carbohydrate and nitrogen supplementation on fermentation of cheatgrass () in a dual-flow continuous culture system.
abstract: Cheatgrass (CG; ), an introduced winter annual grass, is an aggressive invader of the sagebrush community in the Western United States. Because of its greater flammability, mature CG constitutes a fire hazard leading to repeated wildfires. One fuel-reduction strategy is livestock grazing. The objective of this study was to evaluate the effects of urea, molasses, or a combination of urea and molasses supplementation of a CG-based diet on digestibility, microbial fermentation, bacterial protein synthesis, and nutrient flow using a dual-flow continuous culture system. Eight fermenters were used in a replicate 4 × 4 Latin square design with four 10-d experimental periods. Experimental treatments (DM basis) were 1) forage only (CON), 2) CG plus urea alone (URE; 1.36% urea), 3) CG plus molasses alone (MOL; 15.9% molasses), and 4) CG plus urea and molasses combined (URE+MOL; 1.28% urea plus 19.3% molasses). Each fermenter was fed 72 g/d of DM, and data were analyzed using the GLIMMIX procedure of SAS (SAS Inst. Inc., Cary, NC). The true digestibilities of NDF and ADF were not affected by diets ( > 0.05). Molasses-containing diets had greater true digestibility of OM ( = 0.02). However, true digestibility of CP was increased when molasses was fed alone ( < 0.01). Molasses-containing diets had lower pH ( < 0.01) and greater VFA concentrations ( < 0.01) compared to those of the other diets. The URE+MOL diet resulted in a greater VFA concentration ( < 0.01). Propionate concentration increased ( < 0.01), whereas acetate concentration decreased ( < 0.01) when molasses alone or in combination with urea was added to the diets. Supplying molasses alone resulted in greater ( = 0.03) total branched-chain VFA compared to the other diets. The concentration of NH-N and total N flow increased ( < 0.01) in response to urea supplementation and was greater ( < 0.01) when urea alone was supplemented in the diet. On the other hand, molasses-supplemented diets yielded more non-ammonia N ( < 0.01) and bacterial N ( = 0.04). Supplementation had no effect ( = 0.83) on bacterial efficiency. Results from this study indicate that the addition of urea and molasses in a CG-based diet could improve nutrient supply to animals, notably VFA supply and microbial N supply; however, in the levels tested in this study, it did not improve CG utilization as assessed by NDF digestion.
authors.forename: L G
authors.initials: LG
authors.lastname: Silva
authors.forename: P D B
authors.initials: PD
authors.lastname: Benedeti
authors.forename: E M
authors.initials: EM
authors.lastname: Paula
authors.forename: F
authors.initials: F
authors.lastname: Malekjahani
authors.forename: P M
authors.initials: PM
authors.lastname: Amaral
authors.forename: L D S
authors.initials: LD
authors.lastname: Mariz
authors.forename: T
authors.initials: T
authors.lastname: Shenkoru
authors.forename: A P
authors.initials: AP
authors.lastname: Faciola
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D019149:Bioreactors / Q000662:veterinary; D031724:Bromus / Q000378:metabolism*; D002241:Carbohydrates / Q000494:pharmacology*; D002417:Cattle; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements / Q000032:analysis; D004063:Digestion / Q000187:drug effects; D005285:Fermentation / Q000187:drug effects*; D008297:Male; D008965:Molasses; D009584:Nitrogen / Q000494:pharmacology*; D012417:Rumen / Q000378:metabolism; D014508:Urea / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D002241:Carbohydrates; D014508:Urea; D009584:Nitrogen