Date of Graduation

2016

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Joe Moritz

Committee Co-Chair

Jacek Jaczynski

Committee Member

Janet Tou

Abstract

Phytases have become a vital part of broiler diets due to their ability to decrease feed cost and potential environmental pollution caused by the use of excessive phosphorus. The objective of the first study was to compare the effects of various inclusions of a Transgenic Phytase Corn (TPC) to a Granulated Bacteria Phytase (GBP) on 21-d broiler performance and tibia mineralization. Treatments varied in non-phytate phosphorus (Negative control (NC) = 0.2, positive control (PC) = 0.4, 0.3, and 0.35), phytase product (TPC or GBP), and phytase dose (500-3000 FTU/kg). A 2x2 factorial analysis was performed with the main effects phytase activity and phytase product. The inclusion of granulated bacterial phytase resulted in increased broiler performance and tibia mineralization compared to the inclusion of transgenic phytase corn. This may be attributed to variations in dispersion of enzyme within the diet or the general efficacy of the expressed enzyme. The inclusion of a commercial phytase at 3,000 FTU/kg increased broiler performance and tibia mineralization compared to inclusion at 500 FTU/kg. These results may be due to a greater reduction of phytate, alleviating anti-nutrient effects.;The objective of the second study was to evaluate the effects three commercial 6-phytase products with a phosphorus deficient diet subjected to increased steam conditioning temperatures on broiler performance and tibia mineralization. Treatments included a negative control, and a negative control with the addition of a Buttiauxella phytase expressed in Trichoderma reesei (B Trich), an E. coli phytase expressed in Pichia pastoris (E Pichia), or an E. coli phytase expressed in Trichoderma reesei (E Trich), steam conditioned at 82, 88, or 93°C, for a total of twelve treatments. Broiler performance and tibia mineralization were analyzed using a 4 x 3 factorial with the main effects of product and conditioning temperature. The commercial phytase products demonstrated differences in supporting the phosphorus requirement in broilers. Increasing conditioning temperatures had a detrimental effect on broiler performance and tibia mineralization. The increased conditioning temperatures may have decreased nutrient availability, denatured phytase products, or both of these events may have influenced the results.

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