Date of Graduation


Document Type


Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level



Poultry Science


Park W. Waldroup

Committee Member

Fred D. Clark

Second Committee Member

William E. Huff

Third Committee Member

Charles F. Rosenkrans


Biological sciences, Health and environmental sciences, Amino acids, Broiler chickens, Broilers, Poultry nutrition, Protein, Valine


Rising feed costs, environmental pollution concerns targeted at animal agriculture, a worldwide focus on sustainability and the never ending battle to improve production and efficiency within the poultry industry challenges nutritionists to focus on products to improve nutrient digestibility and decrease feed costs while at the same time maximizing performance. The research presented in this dissertation focuses on improving nutrient utilization of protein sources with protein liberating enzymes currently available commercially. The research also conducted addresses the addition of crystalline amino acids valine and isoleucine and their effect on improving efficiency of broilers.

The first research project compared the efficacy of two commercially available protease enzymes; Ronozyme ProAct (DSM, Parsippany, NJ) and Cibenza DP-100 (Novus International, St. Charles, MO). Both are broad spectrum proteases that claim to improve protein digestibility.

The protein source in the broiler diet is one of the most expensive ingredients. For the past fifty years broiler diets have been supplemented with essential amino acids such as methionine and lysine and more recently threonine further reducing crude protein and at the same time decreasing diet cost. The next series of studies were conducted to evaluate the efficacy of reducing crude protein with the addition of the crystalline amino acids valine isoleucine and glycine along with those supplemental amino acids already commercially available.