Phytase effects on broiler growth and gut-level inflammatory responses are influenced by dietary phosphorus level and litter types
A total of 768 broilers were used to study the influence of phytase supplementation in broilers raised on new or old litters and receiving diets with low or high levels of available P (aP). The litter from previous experiment was used as a source of mild challenge to the birds. The birds were allocated at 1 d old to 12 treatments in a 2 × 2 × 3 factorial arrangement with 2 levels of aP (0.3%, negative control or NC; and 0.45%, positive control or PC), 2 types of litter (new or old) and 3 levels of phytase (0, 1,000, and 2,000 FYT/kg). On d 22, sections of jejunum and ileum were collected for histomorphology, jejunal tissues were collected for analysis of expressions of gut-level cytokines (IL) and toll-like receptors (TLR), and tibias were collected for bone ash. There were no 3-way interactions or litter effect for any of the growth performance and tibia mineralization responses but aP × phytase interaction was significant (P < 0.05) for growth performance, except for feed intake. Phytase supplementation improved (P < 0.01) weight gain, tibia ash and FCR in NC but not PC diets. Jejunal villi height:crypt depth decreased (P < 0.05) with phytase supplementation. Ileal villi tended (P < 0.10) to be longer in birds on old litter whereas crypt was deeper (P < 0.05) in birds on NC diets. The 3-way interaction was significant (P < 0.05) for IL1β for which expression was highest (P < 0.05) in birds on old litter and receiving NC diet supplemented with 1000 FYT/kg. Phytase supplementation increased (P < 0.05) IL6 and TLR2 expressions. There were trends (P < 0.10) for phytase × litter for IL6 and TLR2 expressions with phytase increasing (P < 0.05) IL6 expression in birds on new litter and TLR2 expression in birds on old litter. The birds on old litter had higher TLR4 (P < 0.05) expression. We concluded that the effects of phytase on growth performance depended largely on amount of dietary aP whereas phytase effect on gut-level inflammatory responses was more dependent on the litter the birds are raised on.
Other Titles/Title of Conference
Poultry Science Association Meeting, Corpus Christi, USA
93 (E-Suppl. 1)