Date of Graduation


Document Type


Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level



Poultry Science


Craig N. Coon

Committee Member

Sami Dridi

Second Committee Member

Charles V. Maxwell

Third Committee Member

David L. Kreider


15N-phen, Breast Meat Yield, GC-MS, Gene Expression, Protein Turnover, White Striping


Protein turnover in skeletal tissue for broiler breeders has shown to increase at sexual maturity and then decline with increased egg production. Regarding broiler chickens the industry is facing two situations that need to be clarified: the appearance of white stripes in birds over 56 days of age and the positive effect in breast meat yield that supplementation of 25OH-D3 is causing. A series of studies were conducted to determine the effect of sexual maturity in protein turnover in broiler breeders and laying hens and to understand the effect of 25OHD3 in breast meat yield in broiler chickens and why white striping occurs in birds older than 56 days of age. In the first trial, a 4x6 factorial study was conducted to determine the effect of sexual maturity on protein turnover in broiler breeder pure line (4 lines x 6 ages). Results showed that as the birds enter sexual maturity the degradation rate significantly increased and then it decreased as they pass peak egg production, suggesting that they might be relying on their muscle protein reserves for egg formation. In the second trial, a 4x10 factorial study was conducted to evaluate the effect of four different programs and sexual maturity in broiler breeder pullets and hens. Results showed no difference regarding protein turnover between feeding programs. Fractional breakdown rate showed the same pattern as the first trial. In the third trial, a study was conducted to evaluate the effect of sexual maturity on protein turnover in laying hens. Results showed that also in this birds, as they reach peak egg production, the fractional breakdown rate significantly increased. In the fourth trial, a study was conducted to track labeled leucine from the breast of the hens to the egg. Results showed, that hens are using their skeletal muscle for egg formation, since we were able to find labeled leucine in the egg. The last two trials were conducted in broiler chickens to understand the white striping issue and how 25OHD3 enhances muscle growth. We were able to conclude, that birds with severe white striping have a higher protein fractional breakdown rate than the birds with no white stripes. Results regarding 25OHD3 showed that this supplement is enhancing muscle growth through the mTOR pathway.