title: Effects of phytate and phytase on the performance and immune function of broilers fed nutritionally marginal diets.
abstract: The effects of phytate and phytase on broiler performance and cellular and humoral immunity was assessed by using 504 Cobb 500 female broilers fed nutritionally marginal diets. At 1 d of age, the chicks were randomly allocated to 6 treatments in a 2 x 3 factorial arrangement including 2 levels of phytate P (0.22 or 0.44%) and 3 dose rates of an Escherichia coli-derived phytase [0, 500, or 1,000 phytase units (FTU)/kg of feed]. Both low- and high-phytate diets were corn and soy based with the same nutritional specifications (AME 2,900 kcal/kg, CP 21.00%, Ca 0.78%, and nonphytate P0.28%), differing only in the concentration of phytate P. The immune status of birds was measured at 14, 21, and 28 d of age. The results revealed that phytase improved feed intake, BW, and feed conversion ratio (P < 0.05), whereas high dietary phytate depressed bird performance (P < 0.05). There was no interaction between phytate and phytase on bird performance. Feeding phytase increased the percentages of erythrocyte rosette-forming cells and erythrocyte-antibody complement cells by 3.03 and 1.83% at d 21, and by 2.76 and 2.20% at d 28, respectively (P < 0.05). The percentages of CD4(+)CD8(+) T lymphocyte subsets were also increased by phytase (P < 0.05), without affecting the ratio of CD4(+) and CD8(+). The levels of intestinal secretory IgA were improved with phytase at d 14, 21, and 28 (P < 0.05). Antibodies against Newcastle disease virus vaccine were enhanced at d 21 and 28 in the high-phytate diets with phytase addition (P < 0.05). Increasing the phytase dose to 1,000 FTU/kg did not improve immune function further than 500 FTU/kg. The results suggest that application of phytase in nutritionally marginal diets could enhance lymphocyte numbers and the seral and mucosal antibodies of 1- to 28-d-old broilers, suggesting that both phytate and phytase may have a role in gastrointestinal health and immune competence.
authors.affiliation: Faculty of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China, 730070, USA.
authors.forename: N
authors.initials: N
authors.lastname: Liu
authors.forename: Y J
authors.initials: YJ
authors.lastname: Ru
authors.forename: A J
authors.initials: AJ
authors.lastname: Cowieson
authors.forename: F D
authors.initials: FD
authors.lastname: Li
authors.forename: X Ch
authors.initials: XCh
authors.lastname: Cheng
mesh_terms: D010832:6-Phytase / Q000494:pharmacology*; D000821:Animal Feed; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002645:Chickens / Q000276:immunology / Q000502:physiology*; D004926:Escherichia coli / Q000201:enzymology; D029968:Escherichia coli Proteins / Q000494:pharmacology; D007070:Immunoglobulin A / Q000378:metabolism; D007413:Intestinal Mucosa / Q000187:drug effects / Q000276:immunology; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology*; D009753:Nutritive Value; D010833:Phytic Acid / Q000494:pharmacology*
chemical_list: D029968:Escherichia coli Proteins; D007070:Immunoglobulin A; D010833:Phytic Acid; D010832:6-Phytase