title: Dietary microbial phytase exerts mixed effects on the gut health of tilapia: a possible reason for the null effect on growth promotion.
abstract: The present study evaluated the effects of dietary microbial phytase on the growth and gut health of hybrid tilapia (Oreochromis niloticus ♀×Oreochromis aureus ♂), focusing on the effect on intestinal histology, adhesive microbiota and expression of immune-related cytokine genes. Tilapia were fed either control diet or diet supplemented with microbial phytase (1000 U/kg). Each diet was randomly assigned to four groups of fish reared in cages (3×3×2 m). After 12 weeks of feeding, weight gain and feed conversion ratio of tilapia were not significantly improved by dietary microbial phytase supplementation. However, significantly higher level of P content in the scales, tighter and more regular intestinal mucosa folds were observed in the microbial phytase group and the microvilli density was significantly increased. The adhesive gut bacterial communities were strikingly altered by microbial phytase supplementation (0·41<similarity coefficient<0·54). Stimulated intestinal inflammation and stress status were observed in the fish fed diet supplemented with microbial phytase, as indicated by the up-regulated intestinal expressions of the cytokine genes (tnf-α and tgf-β) and hsp70. In addition, the gut microvilli height was significantly decreased in the phytase group. These results indicate that dietary microbial phytase may exert mixed effects on hybrid tilapia, and can guide our future selection of phytases as aquafeed additives - that is, eliminating those that can stimulate intestinal inflammation.
authors.affiliation: 1College of Fisheries,Huazhong Agricultural University,Wuhan,Hubei Province 430070,People's Republic of China.
authors.forename: Jun
authors.initials: J
authors.lastname: Hu
authors.affiliation: 2Key Laboratory for Feed Biotechnology of the Ministry of Agriculture,Feed Research Institute,Chinese Academy of Agricultural Sciences,No. 12 Zhongguancun South St.,Beijing 100081,People's Republic of China.
authors.forename: Chao
authors.initials: C
authors.lastname: Ran
authors.affiliation: 2Key Laboratory for Feed Biotechnology of the Ministry of Agriculture,Feed Research Institute,Chinese Academy of Agricultural Sciences,No. 12 Zhongguancun South St.,Beijing 100081,People's Republic of China.
authors.forename: Suxu
authors.initials: S
authors.lastname: He
authors.affiliation: 2Key Laboratory for Feed Biotechnology of the Ministry of Agriculture,Feed Research Institute,Chinese Academy of Agricultural Sciences,No. 12 Zhongguancun South St.,Beijing 100081,People's Republic of China.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Cao
authors.affiliation: 2Key Laboratory for Feed Biotechnology of the Ministry of Agriculture,Feed Research Institute,Chinese Academy of Agricultural Sciences,No. 12 Zhongguancun South St.,Beijing 100081,People's Republic of China.
authors.forename: Bin
authors.initials: B
authors.lastname: Yao
authors.affiliation: 3School of Biology & Basic Medical Sciences,Soochow University,Suzhou, Jiangsu215123,People's Republic of China.
authors.forename: Yuantu
authors.initials: Y
authors.lastname: Ye
authors.affiliation: 1College of Fisheries,Huazhong Agricultural University,Wuhan,Hubei Province 430070,People's Republic of China.
authors.forename: Xuezhen
authors.initials: X
authors.lastname: Zhang
authors.affiliation: 2Key Laboratory for Feed Biotechnology of the Ministry of Agriculture,Feed Research Institute,Chinese Academy of Agricultural Sciences,No. 12 Zhongguancun South St.,Beijing 100081,People's Republic of China.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Zhou
mesh_terms: D010832:6-Phytase / Q000009:adverse effects / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D017756:Aquaculture; D016207:Cytokines / Q000235:genetics / Q000378:metabolism*; D019587:Dietary Supplements; D005656:Fungal Proteins / Q000494:pharmacology; D000069196:Gastrointestinal Microbiome / Q000187:drug effects*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D007249:Inflammation / Q000139:chemically induced* / Q000378:metabolism; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism; D007421:Intestine, Small / Q000187:drug effects* / Q000378:metabolism / Q000382:microbiology; D010758:Phosphorus / Q000378:metabolism; D013312:Stress, Physiological; D017210:Tilapia / Q000254:growth & development / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D016207:Cytokines; D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; D010758:Phosphorus; D010832:6-Phytase
keywords: Adhesive bacteria; Cs
                  similarity coefficient; Cytokines; Gut; Microbial phytase; Tilapia