Effect of Composition of Feed Model Systems on Pellet Quality: A Mixture Experimental Approach. I

The quality of pelleted feeds is dependent on several variables among which formulation is recognized as having the heaviest influence. An experiment was conducted to investigate the functional properties of feed ingredient components when these ingredients were blended at different proportions on the physical quality of pelleted feeds as measured by the pellet durability index (PDI). Thirteen treatments consisting of different inclusion levels of corn, soybean meal, and soybean oil were designed and a total of 18 batches manufactured, processed, and tested for PDI. Three-dimensional plots were used to depict the relationships between composition of the formulations and PDI. Results showed only a weak dependence of the response on the starch levels in the formulas and the degree of starch gelatinization. Protein, especially from soybean meal, had a positive effect on PDI, whereas a strong negative effect was observed following fat inclusion in the mixer at levels >6.5%. Empirical equations devise...