title: Influence of limestone and phytase on broiler performance, gastrointestinal pH, and apparent ileal nutrient digestibility.
abstract: An experiment was conducted to determine the influence of 2 levels of dietary Ca from limestone and 3 levels of phytase on broiler performance, bone ash, gastrointestinal pH, and apparent ileal digestibility (AID) of Ca, P, and amino acids. Cobb 500 broilers (n = 576) were allowed access to one of 6 corn-soy diets from 0 to 16 d. Experimental diets contained 1.03% or 0.64% Ca from limestone and 0.61% total P. Each diet was supplemented with 0, 500, or 5,000 FTU/kg of phytase to create a 2 × 3 factorial experiment. Broiler feed intake (FI) and BW gain were not affected by dietary Ca or phytase. Feed conversion ratio was improved (P < 0.05) as dietary phytase increased (1.36, 1.34, and 1.31, respectively). Tibia ash percent was reduced (P < 0.05) from 41.4 to 40.0% as dietary Ca decreased but increased with phytase addition (P < 0.05). Gizzard and ileal pH were reduced (P < 0.05) in broilers fed 0.64% Ca compared with broilers fed 1.03% Ca. Phytase at 5,000 FTU/kg increased (P < 0.05) pH in the gizzard, duodenum, jejunum, and ileum. Apparent ileal P digestibility was increased (P < 0.05) in broilers fed 0.64% Ca compared with broilers fed 1.03% Ca (0.68 vs. 0.73, respectively). Apparent ileal Ca digestibility was increased (P < 0.05) in broilers fed 1.03% Ca compared with broilers fed 0.64% Ca (0.67 vs. 0.53, respectively). Phytase improved AID of CP in broilers fed 1.0% Ca but did not have an effect on AID of CP in broilers fed 0.64% Ca, which resulted in a Ca × phytase interaction (P < 0.05). In conclusion, high dietary Ca increased pH in gizzard and ileum and interfered with the AID of P and CP. The interactions between Ca and phytase in the gastrointestinal tract are complex, and feeding phytase at doses above industry recommendations may allow for reduced-Ca diets while maintaining broiler performance, bone ash, and improving amino acid digestibility.
authors.affiliation: AB Vista Feed Ingredients, Marlborough, Wiltshire, SN8 4AN, United Kingdom. Carrie.Walk@abagri.com
authors.forename: C L
authors.initials: CL
authors.lastname: Walk
authors.forename: M R
authors.initials: MR
authors.lastname: Bedford
authors.forename: A P
authors.initials: AP
authors.lastname: McElroy
mesh_terms: D010832:6-Phytase / Q000008:administration & dosage*; D000596:Amino Acids / Q000378:metabolism; D000821:Animal Feed / Q000032:analysis; D000822:Animal Husbandry; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002119:Calcium Carbonate / Q000008:administration & dosage*; D002645:Chickens / Q000254:growth & development / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D004063:Digestion; D004926:Escherichia coli / Q000737:chemistry; D041981:Gastrointestinal Tract / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007082:Ileum / Q000378:metabolism; D008297:Male; D010843:Pichia / Q000737:chemistry; D011897:Random Allocation; D013977:Tibia / Q000737:chemistry
chemical_list: D000596:Amino Acids; D010832:6-Phytase; D002119:Calcium Carbonate