Bacterial concentration reduction in swine waste amended livestock feed using a single-screw dry-extrusion process

• Published in: Bioresource technology Vol. 75; no. 3; pp. 189 - 195
• Main Authors: Kelley, Timothy R., Walker, Paul M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.12.2000; Elsevier Science
• Subjects: Bacteria; bacterial contamination; Biological and medical sciences; coliform bacteria; Concentration reduction; corn; Dry-extrusion; Escherichia coli; extrusion; Feed and pet food industries; Food industries; Food microbiology; Fundamental and applied biological sciences. Psychology; Geobacillus stearothermophilus; heat tolerance; Livestock feed; livestock feeds; monitoring; soybean hulls; spore-forming bacteria; swine; Swine waste; temperature; wastes; Swine waste; Bacteria; Livestock feed; Concentration reduction; Dry-extrusion; Dry process; Escherichia coli; Coliforms; Vegetal waste; Pig; Vertebrata; Mammalia; Pathogenic; Waste reuse; Artiodactyla; Single screw extruder; Biological contamination; Animal waste; Ungulata; Enterobacteriaceae; Feed; Thermomechanical treatment
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/S0960-8524(00)00063-8

A study was conducted to determine the efficiency of a dry-extrusion process to reduce or eliminate bacterial contamination of swine waste amended livestock feed. Separated swine waste solids were mixed with ground corn and soybean hulls and dry-extruded at temperatures of 110–135°C for no more than 30 s to produce animal feed. Swine waste, pre- and post-extrusion livestock feed, and commercial swine feed samples were collected aseptically and analysed for total coliform, Escherichia coli, fecal coliform, heterotrophic, and non-specific anaerobic/facultative bacteria using standard culturing techniques. Selected pre-extrusion feed samples were inoculated with liquid cultures of Bacillus stearothermophilus to test efficiency of the dry-extrusion process to eliminate heat-resistant spore-forming bacteria. Bacterial concentrations recovered from post-extrusion livestock feed were significantly reduced from other sample types analysed. Based on these data, it is apparent that a single-screw, dry-extrusion process can consistently disinfect animal feed. However, careful monitoring of the extrusion process may be necessary for consistent sterilization.