title: Effects of phytase supplementation in broiler diets on a natural Eimeria challenge in naive and vaccinated birds.
abstract: Our study was conducted to determine the effects of dietary phytase on a natural Eimeria challenge in naive and vaccinated broilers. Prior to the experiment the litter was seeded with Eimeria by orally infecting 10-d-old chicks with a cocktail containing 100,000 and 5,000 sporulated Eimeria acervulina and Eimeria tenella oocysts, respectively. Straight-run broiler chicks were placed across 48 floor pens on fresh or seeded litter. Eight treatment combinations were created to include 2 dietary Ca-nonphytate P (npP) levels [0.9% Ca, 0.45% npP; 0.7% Ca, 0.35% npP, 500 phytase units of Optiphos phytase (JBS United, Sheridan, IN)], unchallenged versus challenged, and unvaccinated versus vaccinated groups of chicks. Body weights and feed consumption (FC) were recorded on d 10, 18, and 21. A total of 10 birds/treatment were killed on d 10 and 18 to obtain tissue samples from the duodena and ceca for lesion scoring and cytokine response measurement. At 21 d of age, the left tibia was removed from 18 birds/treatment to assess bone strength. Body weight, FC, and bone strength were unaffected (P > 0.05) by diet or vaccination. By d 21, birds exposed to coccidia had lower FC (P < 0.01), higher feed conversion (P < 0.001), and decreased bone strength (P < 0.01) compared with those not challenged. Regardless of treatment, gross and microscopic scoring of the intestines showed few differences (P > 0.05). Expression of interferon-γ did not differ (P > 0.05) in the duodena or ceca at either time point. The IL-17 gene expression was increased (P < 0.05) in phytase-supplemented, vaccinated, or challenged birds by 18 d of age, with significant interactions (P < 0.05) occurring between birds challenged and fed the marginal diet or vaccinated. Phytase supplementation was unable to provide additional benefits to performance or P utilization in birds vaccinated, subjected to a coccidiosis infection, or both. Based on cytokine production in the intestinal tract on d 10 and 18 postchallenge, the response to the Eimeria challenge was characterized by a T-helper type (Th) 17-like immune response and to a lesser extent a Th1-like immune response, whereas no Th2 cytokine was detected.
authors.affiliation: Department of Poultry Science, Auburn University, Auburn, AL 36849, USA. hendral@auburn.edu
authors.forename: A L
authors.initials: AL
authors.lastname: Shaw
authors.forename: F W
authors.initials: FW
authors.lastname: van Ginkel
authors.forename: K S
authors.initials: KS
authors.lastname: Macklin
authors.forename: J P
authors.initials: JP
authors.lastname: Blake
mesh_terms: D010832:6-Phytase / Q000008:administration & dosage*; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002645:Chickens; D003048:Coccidiosis / Q000276:immunology / Q000469:parasitology / Q000517:prevention & control / Q000662:veterinary*; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics; D004435:Eating / Q000187:drug effects; D004539:Eimeria / Q000276:immunology*; D005243:Feces / Q000469:parasitology; D007411:Intestinal Diseases, Parasitic / Q000276:immunology / Q000469:parasitology / Q000662:veterinary*; D016018:Least-Squares Analysis; D010270:Parasite Egg Count / Q000662:veterinary; D010865:Pilot Projects; D011201:Poultry Diseases / Q000276:immunology / Q000469:parasitology* / Q000517:prevention & control; D016053:RNA, Protozoan / Q000737:chemistry / Q000235:genetics; D011897:Random Allocation; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary
chemical_list: D016207:Cytokines; D016053:RNA, Protozoan; D010832:6-Phytase