Effect of level of intake and supplemental barley on marker estimates of fecal output using an intraruminal continuous-release chromic oxide bolus
1991
Hatfield, P.G. | Walker, W. | Glimp, H.A. | Adams, D.C.
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 200g/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 < .05). No differences (P > .50) were detected in Exp. 3 and 4. In Exp. 1, 2, and 3 accuracy was different (P < .02) among wethers within study and treatment. Only in Study 4 were minor or no differences (P > .09) in accuracy found. Accuracy (Exp. 1, 2, and 3) and precision (Exp. 1 and 2) of marker-estimated fecal output seemed to be affected by level of DMI and supplemental barley. These data indicate that total fecal collections on a subset of animals used in a study may be necessary to adjust marker estimates of fecal output.
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