title: Effect of level of intake and supplemental barley on marker estimates of fecal output using an intraruminal continuous-release chromic oxide bolus.
abstract: Sixty wethers (average BW = 45 kg) fitted with fecal collection bags were used in four experiments to evaluate the ability of a intraruminal continuous-release chromic oxide bolus to predict fecal DM output. In Exp. 1, 18 wethers housed in metabolism crates were fed barley at either 0, 100, or 200g/d and allowed ad libitum consumption of alfalfa pellets. In Exp. 2, 18 wethers were housed in metabolism crates and fed alfalfa pellets at either 70, 85, or 125% of pre-study ad libitum consumption. In Exp. 3, 12 wethers grazed a sagebrush-bunchgrass range and were individually fed barley at 0 or 200 g/d. In Exp. 4, 12 wethers grazed either an ungrazed (383 kg/ha herbaceous biomass) or a heavily grazed (175 kg/ha herbaceous biomass) sagebrush-bunchgrass range. Experiments 1 and 2 were balanced 3 x 3 Latin squares, and Exp. 3 and 4 were crossover designs. Chromium content was determined in rectal grab samples. Treatment effects were compared using marker-estimated fecal output divided by total fecal collection, multiplied by 100, as the dependent variable. Accuracy of the estimate was verified by comparing marker-estimated fecal output with total fecal collection using a paired t-test. In Exp. 1 and 2, treatments were different (P less than .05). No differences (P greater than .50) were detected in Exp. 3 and 4. In Exp. 1, 2, and 3 accuracy was different (P less than .02) among wethers within study and treatment. Only in Study 4 were minor or no differences (P greater than .09) in accuracy found.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: U.S. Sheep Exp. Sta., ARS, U.S. Department of Agriculture, Dubois ID 83423.
authors.forename: P G
authors.initials: PG
authors.lastname: Hatfield
authors.forename: J W
authors.initials: JW
authors.lastname: Walker
authors.forename: H A
authors.initials: HA
authors.lastname: Glimp
authors.forename: D C
authors.initials: DC
authors.lastname: Adams
mesh_terms: D000821:Animal Feed; D000818:Animals; D002857:Chromium / Q000008:administration & dosage; D017608:Chromium Compounds; D003672:Defecation / Q000502:physiology*; D003692:Delayed-Action Preparations; D004063:Digestion; D004435:Eating; D001467:Hordeum; D007202:Indicators and Reagents; D008297:Male; D012756:Sheep / Q000502:physiology*
chemical_list: D017608:Chromium Compounds; D003692:Delayed-Action Preparations; D007202:Indicators and Reagents; D002857:Chromium; C023600:chromic oxide