The effect of sieve agitators and dispersing agent on the method of determining and expressing fineness of feed materials by sieving

Research in both swine and poultry continue to investigate the optimal particle size for growth and gut health. Although researchers have reported the methods used to determine the particle size of the grain in a study, most reports have not provided details of the actual procedure. Although the standard method suggested adding both agitators and dispersing agents to facilitate the flow of material through the sieves there has been limited research as to whether these modifiers significantly change the particle size value. Researchers, laboratories, and feed mills that analyse samples without sieve agitators or a dispersing agent could overestimate the particle size and underestimate the distribution of the particles of a sample. Two experiments were conducted to determine the effect of adding sieve agitators and dispersing agent to the ANSI/ASAE S319.3 FEB03 ‘Method of Determining and Expressing Fineness of Feed Materials by Sieving’. The first experiment evaluated the effect of sieve agitator use and dispersing agent use on the geometric mean diameter (dgw) and geometric standard deviation (Sgw) of hammermill and roller mill corn samples. Whole corn was ground to produce samples that were classified as either coarse, medium, or fine. The second experiment evaluated the effect of sieve agitators, a dispersing agent, and the combination of agitators with a dispersing agent on dgw and Sgw of hammermill ground corn, wheat, and sorghum. The results of Expt 1 indicated that a decreased (P < 0.01) dgw resulted when agitators were added to the hammermill ground samples while a further decrease (P < 0.01) was observed due to the addition of the dispersing agent. The largest decrease in dgw was observed due to the addition of the dispersing agent. The addition of agitators to the roller mill samples only decreased the dgw of the medium grind sample. The dispersing agent decreased (P < 0.01) the dgw of roller mill samples. The addition of a dispersing agent consistently decreased the dgw of all the ground corn samples as compared with the standard method without modifiers. The results of Expt 2 were consistent with those of Expt 1 in that the addition of the dispersing agent and agitators decreased dgw values and appeared to have an additive effect in both corn and sorghum samples. The addition of a dispersing agent facilitated the flow of product through the sieves. The wider distribution (Sgw) indicated that a greater percentage of material flowed to the smaller sieves. The results of the experiments clearly showed the benefit of adding sieve agitators and a dispersing agent to facilitate the flow of material through the sieves, so that a better estimate of the micron diameter and particle size distribution could be achieved.