Date of Graduation

12-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level

Graduate

Department

Poultry Science

Advisor/Mentor

Coon, Craig N.

Committee Member

Rath, Narayan C.

Second Committee Member

Maxwell, Charles V.

Keywords

Biological sciences; Broiler breeders; Nutrition; Poultry; Protein requirements

Abstract

Advances in the genetics of poultry have created unintended consequences to the broiler breeder industry. Excessive weight has been shown to have many negative effects, including double hierarchies, multiple ovulations, and fatty liver. In an effort to curb excessive body weight gain, both the protein requirements and feeding strategies of broiler breeders are being revisited. A series of studies were conducted to determine the protein and amino acid requirements of broiler breeders during the production phase and to determine the interrelationship between protein turnover and egg formation. In the first trial, a 2x3x3 factorial study was conducted to determine the optimal energy x crude protein x pullet body weight combination to maximize egg production, fertility, and offspring weight. Results showed that 390 kcal and 22g CP were sufficient to optimize broiler breeder productivity. Protein utilization and nitrogen retention were most efficient at 22g CP intake. In the second trial, a 2x3 factorial study was conducted to determine how energy and crude protein impacts the partitioning of lysine during the egg formation process. Over 78% of dietary lysine was diverted towards egg formation, with the remaining being partitioned towards egg formation. However, the lysine in the egg was not solely of dietary origin. During early lay and at 45 wk, a majority of the lysine found in the egg yolk was from endogenous origins. Albumen was found to consist of primarily dietary lysine. No effect of energy and crude protein on portioning was determined. In the third trial, a 2x3 factorial study was conducted to determine the effects of energy and crude protein on protein turnover and the expression of proteolysis-related genes. Fractional degradation rates were found to increase during early lay and at 45 wk, but not at peak production. Expression of Fbox 32 protein, an indicator of ubiquination, was found to be elevated at the same periods degradation rates were found to be elevated. No changes to the proteasome and calpain 2 were observed that would explain changes to degradation rates. In the final two studies, the effects of low non-phytate phosphorus (NPP) on the diurnal patterns of bone turnover and the effects of carnitine supplementation on the fatty acid profiles of a hen and her eggs. Lowering NPP to 0.15% was found to diminish the amount of bone that is mobilized in an attempt to spare the skeletal integrity. Egg production is nonetheless reduced when NPP lowered to 0.15%. Finally, carnitine supplementation was found to increase the concentration of saturated and monounsaturated fatty acids in the egg and decrease the amount of polyunsaturated fatty acids in breeder abdominal fat.

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