Semester

Summer

Date of Graduation

2012

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Joseph S. Moritz.

Abstract

The objective of this study was to identify feed manufacture techniques that alter lysine availability as indicated by broiler performance in the finishing phase, diet furfural content, and true amino acid digestibility. Production rate, pellet die specification, and level of mixer-added fat (MAF) influence feed exposure to pellet die frictional heat and pressure that may alter chemical structure of ingredients. Lysine has been indicated as a nutrient with potential to be structurally altered, especially in the presence of heat and reducing sugars, as in Maillard reactions; decreasing nutrient availability. A practical diet containing 7.5% bakery by-product meal and 0.13% lysine HCl was formulated to 90% of the lysine recommendation by Cobb-Vantress to be below the perceived safety margin associated with breeder recommendations and best demonstrate lysine availability differences when manufactured and fed. This diet was utilized in a 2 x 2 x 2 factorial design that evaluated the main effects of production rate (0.5 or 0.8 tonne/hr), pellet mill die thickness (38.1 or 44.5 mm), and MAF level (0.5 or 3%) on feed manufacture, broiler performance, and processing yield. Two additional treatments: unprocessed mash and double pelleted (exposed twice to 0.5 tonne/hr production using a 4.5mm die after 0.5% MAF) were also manufactured and fed. All diets, excluding mash, were steam conditioned at 82°C and ground prior to feeding. Pellet mill electrical energy usage, pellet quality, and bulk density were increased with 0.5 tonne/hr production rate, 44.5 mm pellet die, and 0.5% MAF processing treatments (P=0.0001); indicating greater feed exposure to pellet die frictional heat and pressure. Bird performance and carcass characteristics were not affected by main effects (P>0.05); however, contrasts demonstrated that mash fed birds had decreased feed conversion ratio (FCR) compared with double pelleted fed birds, with birds fed diets from the factorial treatments being intermediate (P<0.05). To determine if the mechanism of action responsible for the FCR effects included lysine digestibility, diets were analyzed for furfural, an intermediate of the Maillard reaction pathway, and assessed for true amino acid digestibility using cecectomized roosters. Furfural concentration was not altered due to processing treatment (P > 0.05). In addition, no differences in lysine digestibility or the digestibility of any other tested amino acid were apparent (P > 0.05). Therefore, lysine availability, as assessed with this specific methodology, does not appear to be decreased due to pelleting.

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