The effects of different methods of estimating fecal output on plasma cortisol, fecal output, forage intake, and weight change in free-ranging and confined wethers.
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Thirty-four white-face wethers (avg BW 56 kg) were used in two experiments to investigate differences in plasma cortisol, forage intake, fecal output, and BW change associated with two methods of estimating fecal output. The methods were fecal collection bags (B) and marker estimates of fecal output (U). A control treatment (C) was included in each experiment in which wethers were not bagged or dosed with the marker. Experiment 1 was conducted with wethers grazing dormant sagebrush-bunchgrass range. Experiment 2 was conducted with wethers housed in metabolism crates. In Exp. 1, the following differences were detected: 1) basal and mean integrated (following ACTH challenge) plasma cortisol levels were higher (P < .05) for U wethers than for C wethers, 2) no differences (P > .05) between B and C wethers were detected for basal or mean integrated plasma cortisol, 3) both B and U wethers gained (P < .05) weight, whereas C wethers lost weight, and 4) no differences (P > .05) between B and U wethers were detected for cortisol measurements, weight change, or fecal output. No differences (P > .05) were noted for any of the variables tested in Exp. 2. When treatments were combined within experiment to test Exp. 1 vs 2, time to peak cortisol levels was longer (P < .05) and mean integrated cortisol levels and weight change were lower (P < .05) for wethers in confinement than for wethers on range. No difference (P > .05) was detected for basal cortisol levels.(ABSTRACT TRUNCATED AT 250 WORDS)