Theses and Dissertations

Issuing Body

Mississippi State University


Wamsley, Kelley G. S.

Committee Member

Zhai, Wei

Committee Member

Kiess, Aaron S.

Committee Member

Rochell, Samuel

Date of Degree


Original embargo terms

Visible to MSU only for 1 year

Document Type

Dissertation - Open Access


Poultry Science

Degree Name

Doctor of Philosophy


College of Agriculture and Life Sciences


Department of Poultry Science


Currently, feed enzyme supplementation into commercial broiler diets is a routine practice due to hydrolysis of antinutrients, such as non-starch polysaccharides (NSP) and phytate (IP6); ultimately leading to optimized broiler production. As a result, the market has grown rapidly, and a multitude of feed enzymesare commercially available. Complete removal of antinutrients has not been achieved and research has primarily focused on the use of singular enzyme inclusion. Due to biochemical differences among enzyme characteristics, there may be potential for synergistic action to remove antinutrients and further maximize broiler performance. Therefore, the overall objective of this dissertation was to investigate enzyme strategies to determine optimal inclusion for broilers. Chapter 2 investigated the interactive effects of phytase dose (PD; 250 to 1500 FTU/kg) and carbohydrase enzyme (CE) of xylanase (XAN), β-mannanase (MAN), or their combination (XM). These data demonstrated an interaction between CE and PD for d 0-14 FCR, but this significance was lost during the remainder of the study. Overall benefits for performance and processing were demonstrated with feeding a PD of 1500 FTU/kg and XAN. Chapter 3 took a preliminary approach (0-14 d) to investigate the potential synergy among 3 phytase enzymes of varying biochemical properties when fed alone or in combination with low PD (120 or 240 FTU/kg). These data demonstrated potential synergy with the supplementation of 2 phytases combined at a higher PD (240 FTU/kg), as identified from ileal IP (inositol phosphate) lower ester concentration and tibia ash. Chapter 4 built upon the previous chapter, choosing 2 phytases (A or B) and addressing previous limitations by including a broader/more practical range of phytase activity (250 or 1500 FTU/kg); providing 3 diets varying in calcium (Ca) and non-phytate phosphorus (nPP); and using an entire grow-out. Feeding diets lowest in Ca and nPP along with 1500 FTU/kg of A, B, or A+B resulted in improved broiler performance. Additionally, the use of A+B at 250 FTU/kg within diets of medium Ca and nPP levels demonstrated synergism through improved broiler performance and tibia ash. Overall, data suggest that the strategic utilization of enzyme combinations may provide additional benefits towards broiler production.