Date of Graduation

12-2023

Document Type

Thesis

Degree Name

Master of Science in Poultry Science (MS)

Degree Level

Graduate

Department

Poultry Science

Advisor/Mentor

Kidd, Michael T.

Committee Member

Kegley, Elizabeth B.

Second Committee Member

Sun, Xiaolun

Keywords

Amino Acids; Carcass Characteristics; Digestible Lysine; Live Performance; Metabolizable Energy; Net Energy

Abstract

As a result of the advancement of genetics, understanding broiler requirements for dietary energy and amino acids is essential for improving live performance and carcass characteristics. The energy system used to formulate diets in poultry is based on metabolizable energy (ME); this equation can be described as the total amount of energy in the feed minus gases and feces. However, the net energy (NE) system may be the best depiction of the energy utilized by birds for production and maintenance purposes once the heat increment (HI) is measured. Thus, a series of studies were conducted to establish the responsiveness of broilers (Cobb 500 and Ross 708) fed varying dietary energy, amino acid (AA) levels, and energy systems. The experiment in chapter II analyzed the response of Cobb 500 broilers (males) fed varying levels of digestible lysine (dLys) and ME during the starter phase (1 to 18 d) on live performance as well as the carryover effects on carcass characteristics. Birds that were fed increased ME obtained an improved live performance. Additionally, it appears safe to utilize 1.18% dLys to provide the standard results regarding live performance and carcass traits. Experiment 1 (male) and 2 (female) in chapter III served to assess the responsiveness of Ross 708 broiler performance and carcass characteristics to different energy systems and crude protein (CP) formulations. It was determined that male birds fed increased CP levels had decreased feed conversion ratio (FCR) and both sexes decreased fat pads with high CP diets; additionally, male broilers fed decreased CP were more sensitive to dietary energy variations regarding abdominal fat pad deposition. In addition, in chapter III, experiment 3 aimed to evaluate the performance and carcass characteristics of broilers (Cobb 500) at different NE levels and CP during the 32 to 41d finisher period, in addition to comprehending possible interactions between NE formulation and CP. It was established that increasing the levels of NE from 2,250 to 2,400 kcal/kg improved live performance and did not affect the abdominal fat pad. Furthermore, birds fed increased CP had greater live performance and breast meat yield, and decreased fat pad yield.

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