title: Diurnal variation in fecal concentrations of acid-detergent insoluble ash and alkaline-peroxide lignin from cattle fed bermudagrass hays of varying nutrient content.
abstract: BACKGROUND
  The effect of time of fecal sampling on the accuracy of acid-detergent insoluble ash (ADIA) and alkaline-peroxide lignin (APL) for the prediction of fecal output (FO) in cattle was evaluated. Eight ruminally cannulated cows (594 ± 35.5 kg) were allocated randomly to 4 bermudagrass [Cynodon dactylon (L.) Pers.] hay diets markedly different in crude protein concentration (79-164 g/kg) with 2 replicates per diet for 3 periods. Cows were offered hay individually at 20 g DM/kg of body weight daily in equal feedings at 08:00 and 16:00 h for a 10-d adaptation period followed by 5-d of total fecal collection. Fecal grab samples also were taken each day during the fecal collection period at 06:00, 12:00, 18:00, and 24:00 h either directly from the rectum or from freshly voided feces. Samples were composited within cow and time across the 5 d total fecal collection period. Additionally, forage, ort, and fecal samples were analyzed for concentrations of APL and ADIA.
  
  
  RESULTS
  Fecal concentrations of ADIA and APL were not affected by sampling time (P ≥ 0.22), even though diet affected (P < 0.01) fecal ADIA and APL concentrations. There were no diet × sampling time interactions (P ≥ 0.60). Estimates of FO and dry matter digestibility (DMD) from ADIA and APL were not affected (P ≥ 0.16) by sampling time or the diet × sampling time interaction (P ≥ 0.74). Estimates of FO and DMD from markers from different sampling times or all different combinations of sampling time were not different (P ≥ 0.72) from those of total collection among internal markers.
  
  
  CONCLUSIONS
  Little variation in concentrations of ADIA and APL in daily fecal excretion across time increases flexibility in fecal grab sampling schedules for predicting FO and DMD.
authors.affiliation: Division of Agriculture, University of Arkansas, Fayetteville, AR 72701 USA.
authors.forename: Juvenal
authors.initials: J
authors.lastname: Kanani
authors.affiliation: Division of Agriculture, University of Arkansas, Fayetteville, AR 72701 USA.
authors.forename: Dirk
authors.initials: D
authors.lastname: Philipp
authors.affiliation: Division of Agriculture, University of Arkansas, Fayetteville, AR 72701 USA.
authors.forename: Kenneth P
authors.initials: KP
authors.lastname: Coffey
authors.affiliation: Division of Agriculture, University of Arkansas, Fayetteville, AR 72701 USA.
authors.forename: Elizabeth B
authors.initials: EB
authors.lastname: Kegley
authors.affiliation: Department of Plant and Soil Science, Texas Tech University, Lubbock, TX 79409 USA.
authors.forename: Charles P
authors.initials: CP
authors.lastname: West
authors.affiliation: Division of Agriculture, University of Arkansas, Fayetteville, AR 72701 USA.
authors.forename: Shane
authors.initials: S
authors.lastname: Gadberry
authors.affiliation: Division of Agriculture, University of Arkansas, Fayetteville, AR 72701 USA.
authors.forename: John
authors.initials: J
authors.lastname: Jennings
authors.affiliation: Division of Agriculture, University of Arkansas, Fayetteville, AR 72701 USA.
authors.forename: Ashley N
authors.initials: AN
authors.lastname: Young
authors.affiliation: Division of Agriculture, University of Arkansas, Fayetteville, AR 72701 USA.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Rhein
keywords: Bermudagrass; Cattle; Digestibility; Fecal sampling time; Internal markers