Date of Graduation


Document Type


Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level



Poultry Science


Nicholas B. Anthony

Committee Member

Susan E. Watkins

Second Committee Member

Jason K. Apple

Third Committee Member

Andy Mauromoustakos


Biological sciences, Divergent selection, Incubation, Myogenesis, Poultry, Response


Genetic selections currently utilized in the poultry industry have been highly successful in promoting broiler growth rate and yield. However, these selections may have come at the expense of broiler physiology, as evidenced by an increase in physiological disorders. To address this experimentation was undergone to develop a novel method of selection to promote growth with minimal physiological impact and to assess how a new embryonic technique affects growth in broiler lines exhibiting different growth rates.

In the first experiment, a random bred control (RAN) broiler line was divergently selected for four-day relative breast yield (BY4) resulting in the high (HBY4) and low (LBY4) BY4 lines. Selection resulted in clear divergence in BY4 of the HBY4 and LBY4 lines over four generations. This was made possible by the high heritabilities calculated for breast weight relative to live weight in both the HBY4 and LBY4 lines. Furthermore, BY4 selections were capable of impacting embryonic development.

In the second experiment, multiple hatches were obtained from selected generation three broiler breeders from the HBY4, LBY4 and unselected RAN lines. Hatches were used to examine correlated responses to selection during a traditional growout period. Results indicate that selection for BY4 was capable of promoting breast percentage at processing age with the HBY4 having a greater breast yield than the LBY4 at 42 and 56 days of age. Furthermore, this change occurred at minimal expense to broiler fitness and with no impact on broiler meat quality at processing age.

In the third experiment, the effects of thermal manipulation (TM) on broiler embryos from two broiler strains expressing differing rates of growth. TM was effective in promoting early growth in both strains compared to their control counterparts, but post Day 35 no difference in body weight was shown between TM and CTRL strains. However, at Day 42 differences in breast percentage between TM and CTRL strains approached significance with TM strains having a greater breast percentage than their CTRL counterparts at 60 days of age. The improved body composition was not accompanied by changes in meat quality parameters between CTRL and TM broilers. Results indicate that TM can be used to improve body composition without impacting meat quality.