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Abstract
Fine-grinding of high-fat animal protein meals often is necessary prior to inclusion in shrimp diets. The effects of pulverizing and defatting two types of poultry by-product meals (regular poultry by-product meal [PBM] and low-ash petfood-grade poultry by-product meal [PBMPG]) and the effects of pulverizing two types of feather meal (hydrolyzed feather meal [FM] and a high-digestibility feather meal [FMHD]) on particle size reduction, moisture loss, and electrical energy consumption were investigated. Pulverizing PBM resulted in a significant reduction in particle size (415 vs. 223 μm; P < 0.05), and defatting resulted in a similar apparent reduction (415 vs. 295 μm; P < 0.05). Defatting and pulverizing PBM resulted in an even greater change in particle size (295 vs. 119 μm; P < 0.05). Defatting PBM reduced grinding energy consumption dramatically (98 vs. 68 Kwh/MT; P < 0.05). Neither pulverizing (371 vs. 336 μm;P > 0.05) nor defatting (371 vs. 245 \im;P> 0.05) significantly reduced particle size for PBMPG. Defatting had no effect on grinding energy (80.5 vs. 79.4 Kwh/MT; P > 0.05) for PBMPG. Pulverizing also significantly reduced particle size for both types ofFM (540 vs. 261 μm for FM, and 492 vs. 154 μm for FMHD; P< 0.05). Furthermore, pulverizing reduced moisture contents of all poultry by-products, especially FM. The average moisture reduction was 2.4% for both PBM and FM.