Influence of phytate and phytase on the digestion and uptake of nutrients in the chicken (Gallus domesticus) and the white pekin duck (Anas platyrinchos domesticus)
Abstract
Phytates have anti-nutritional effects but the mechanisms of most of them are poorly understood. In the first study, the effect of different forms of phytates on endogenous losses in chicken and duck were investigated. The form of phytate affected the extent and nature of endogenous losses. The second study examined the effect of phytate on the uptake of amino acids or glucose from the jejunum in chicken. Presence of phytate decreased the absorption of some specific free amino acids and not others. The third and fourth studies compared efficacies of various phytase sources in overcoming anti-nutritional effects of phytates in broiler chicks. Three phytase sources derived from Escherichia coli and expressed in three different yeast systems were equally efficacious in improving growth and nutrient utilization. Also efficacy of Escherichia coli phytase was compared with that of Peniophora lycii phytase. The Escherichia coli phytase was more efficacious in improving growth and mineral utilization whereas Peniophora lycii phytase was more efficacious in improving ileal digestibility of amino acids. The fifth study compared the two phytase sources for their resistance to hydrolysis in the digestive tract. The Escherichia coli phytase was more resistant than the Peniophora lycii phytase. The sixth and seventh studies investigated the role of dietary composition in the regulation of intestinal phytase. When cholecalciferol concentration in diet was increased there was decreased Km of intestinal phytase in ducklings, but increased Vmax and Km of the enzyme in broiler chicks. When phosphorus concentration in diet was increased there was no change in intestinal phytase activity in ducklings but a decreased Vmax and Km of the enzyme in broiler chicks. In the seventh study, addition of phytate to a chemically defined casein diet reduced the Vmax of the intestinal phytase but the Km of the enzyme was not affected. Hence, intestinal phytase may be regulated by manipulating diet composition.
Degree
Ph.D.
Advisors
Adeola, Purdue University.
Subject Area
Livestock|Anatomy & physiology|Animals
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