title: Dietary fiber content influences soluble carbohydrate levels in ruminal fluids.
abstract: The soluble carbohydrate concentration of ruminal fluid, as affected by dietary forage content (DFC) and/or ruminally undegradable intake protein content (UIPC), was determined. Four ruminally cannulated steers, in a 4 × 4 Latin square design, were offered diets containing high (75 % of DM) or low (25 % of DM) DFC and high (6 % of DM) or low (5 % of DM) UIPC, in a 2 × 2 factorial arrangement. Zinc-treated SBM was the primary UIP source. Soluble hexose concentration (145.1 μM) in ruminal fluid (RF) of steers fed low DFC diets exhibited a higher trend (P = 0.08) than that (124.5 μM) of steers fed high DFC diets. UIPC did not modulate (P = 0.54) ruminal soluble hexose concentrations. Regardless of diet, soluble hexose concentration declined immediately after feeding and did not rise until 3 h after feeding (P < 0.0001). Cellobiose (≈90 %) and glucose (≈10 %) were the major soluble hexoses present in RF. Maltose was not detected. Soluble glucose concentration (13.0 μM) was not modified by either UIPC (P = 0.40) nor DFC (P = 0.61). However, a DFC by post-prandial time interaction was detected (P = 0.02). Pentose concentrations were greater (P = 0.02) in RF of steers fed high DFC (100.2 μM) than steers fed low DFC (177.0 μM). UIPC did not influence (P = 0.35) soluble pentose concentration. The identity of soluble pentoses in ruminal fluid could not be determined. However, unsubstituted xylose and arabinose were excluded. These data indicate that: (i) soluble carbohydrate concentrations remain in ruminal fluid during digestion and fermentation; (ii) slight diurnal changes began after feeding; (iii) DFC influences the soluble carbohydrate concentration in RF; and (iv) UIPC of these diets does not affect the soluble carbohydrate concentration of RF.
authors.affiliation: Animal Science Department, Purdue University, West Lafayette, Indiana, USA.
authors.forename: R S
authors.initials: RS
authors.lastname: Pinder
authors.forename: J A
authors.initials: JA
authors.lastname: Patterson
authors.forename: C A
authors.initials: CA
authors.lastname: O'Bryan
authors.forename: P G
authors.initials: PG
authors.lastname: Crandall
authors.forename: S C
authors.initials: SC
authors.lastname: Ricke
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D050260:Carbohydrate Metabolism; D002417:Cattle / Q000378:metabolism*; D004043:Dietary Fiber / Q000032:analysis* / Q000378:metabolism; D004063:Digestion; D005750:Gastric Juice / Q000737:chemistry*; D012417:Rumen / Q000737:chemistry / Q000378:metabolism*; D013025:Glycine max / Q000737:chemistry