Evaluation of Particle Size Distribution and Ration Uniformity in Total Mixed Rations Fed in Northcentral Texas1,21Funded in part by the Houston Livestock Show and Rodeo and Protiva, a unit of Monsanto.2Presented as part of the 1997 Mid-South Ruminant Nutrition Conference, Irving, TX.
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1998 American Registry of Professional Animal Scientists. Twenty dairies were used to evaluate the effects of mixer design (vertical or horizontal) and mixing time on total mixed ration uniformity and particle size distribution. Samples were collected under two mixing schemes: normal mixing time and normal mixing time plus an additional 15 min. Additional tests evaluated: 1) the effects of altering ingredient loading sequence and 2) whether the addition of high-moisture feeds could alter particle size distribution results. Particle size distribution was measured with the Nasco Forage Particle Size Separator. The Quantab Chloride Titrator kit was evaluated as an indicator of ration nutrient uniformity. Due to large variation among samples taken at each dairy, no generalizations regarding effect of mixer type or mixing time on particle size distribution or ration uniformity can be made. However, additional testing of individual observations yielded interesting results: 1) average particle size distribution of Texas rations was different from the northeastern U.S. ration averages; 2) particle retention on the top screen (>1.905 cm) could be manipulated as much as 30% by altering the inclusion of alfalfa hay from first to third order in the loading sequence; and 3) particle size retention shifted as much as 30% downward from screens 1 + 2 (>0.79 cm) to the bottom pan (<0.79 cm) with rations containing high inclusions of wet brewer's grains, depending on whether the ration was sieved wet or dried prior to sieving. Results from this study demonstrate the potential impact of mixing management on ration quality control to a dairy operation.
