Abstract. Whole shelled corn, black beans, white beans, and fuzzy whole cotton seed were used as tracers in blended total mixed rations to assess uniformity. Tracers were placed in varied locations of two mixers, but under the conditions of these experiments, tracer placement did not affect the coefficient of variation (CV; the uniformity measurement). This is an indication of mixer performance. With a paddle mixer blending a beef ration which did not have much long particle mass, each tracer performed similarly; as mixing time increased from 180 to 600 s, the CV did improve at a rate of 1% reduction per minute – starting at 24.8% with 180 s of mixing. With a reel-type mixer and a dairy ration containing 19% particle mass longer than 19 mm, the type of tracer affected CV. Slick tracers (corn, white beans, black beans) had higher CVs (28%, 33%, and 33%, respectively) than fuzzy whole cotton seed (18%); counts of slick tracers also decreased as the mixer emptied. The clingy whole cotton seed tracer suggested a more uniform blend (lower CV) and there was not a tendency for increase, nor decrease, in cotton seed counts as the mixer emptied. For the stationary reel mixer, increasing mixing time from 350 to 1100 s did not reduce CV. Uniformity of size particle size distribution among samples was better than uniformity of countable tracers for both mixers.