Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design


Animal and Nutritional Sciences

Committee Chair

Joseph S. Moritz

Committee Co-Chair

Kenneth P. Blemings

Committee Member

Janet C. Tou


There are various methods of processing avian diets. However, the two common methods of processing include grinding, batching, mixing, and feeding the resultant mash that is not thermally processed, extrusion processing, baking, and steam conditioning and pelleting. The method of processing utilized can greatly affect nutrient availability, therefore affecting the health and/or performance of the avian. The objective of the first study was to transition cockatiels (Nymphicus hollandicus) that were housed in a controlled experimental setting, with a standardized transition strategy, using two different commercially available cockatiel diets that were advertised as nutritionally complete. The transition strategy consisted of gradually increasing the ratio of complete diet to seed-based diet over a 12d period. True amino acid digestibility was determined for each complete diet and demonstrated that both diets contained highly digestible amino acids. Fourteen cockatiels individually housed in acrylic cages were transitioned to one of the complete diets (Diet A or B). Diet A and B differed in ingredient composition, ingredient particle size, analyzed nutrients, and method of processing (baked or extruded). It may be speculated that cockatiels were more accepting of baked Diet A during transition and Diet A more efficiently maintained BW. The objective of the second study was to determine the effects of pelleting, inclusion of a Bacillus derived keratinase, and bird sex on broiler performance. The keratinase was batched and mixed prior to steam conditioning and pelleting and therefore must be thermally stable to demonstrate efficacy. This study consisted of a 2 x 2 x 2 factorial arrangement of treatments in a randomized complete block design; there was either a ground pelleted or mash diet with or without keratinase supplementation fed to a pen of either male or female Cobb x Cobb 500 broiler chicks. Mash feed was short-term conditioned to a temperature of 82°C and extruded through a 38.1 x 4.76 mm pellet die using a 40 HP California Pellet Mill. Males had enhanced broiler performance as compared to females. The thermal conditions of the pelleting process decreased broiler performance likely due to decreasing nutrient availability. Keratinase activity was reduced due to thermal conditions of pelleting that may have contributed to the lack of enzyme efficacy with respect to broiler performance.