title: Energy, amino acid, and phosphorus digestibility of phytase transgenic corn for growing pigs.
abstract: Three experiments were conducted to evaluate energy, AA, and P digestibility in a phytase transgenic corn (PTC) containing a phytase gene (phyA2) isolated from Aspergillus niger compared with a nontransgenic near-isoline conventional corn (CC) grown in the same environmental conditions for growing pigs. Experiment 1 was an energy balance experiment conducted to measure DE and ME in PTC and CC. Eighteen growing barrows (initial BW 25.8±0.3 kg) from 9 litters were allotted by BW and litter to 1 of 2 dietary treatments with 9 pigs per treatment in a randomized complete block design. Pigs were individually placed in metabolism cages and fed diets based on the 2 corns. The DE and ME in PTC (3,967 and 3,941 kcal/kg of DM, respectively) were greater (P<0.05) than those in CC (3,917 and 3,848 kcal/kg of DM, respectively). Experiment 2 was conducted to measure apparent ileal digestibility (AID) and standardized ileal digestibility (SID) values of CP and AA in the 2 corns. Eighteen growing barrows (initial BW 41.8±0.7 kg) were equipped with a T-cannula in the distal ileum. Pigs were placed in metabolism cages in a completely randomized design with 3 dietary treatments of 6 pigs each. An N-free diet was used to estimate basal endogenous losses of CP and AA. The AID and SID values for CP and all AA did not differ between the 2 corns. Experiment 3 was conducted to measure apparent total tract digestibility (ATTD) and standardized total tract digestibility (STTD) values of P in the 2 corns. Eighteen growing pigs (initial BW 30.5±0.5 kg) from 6 litters were placed in metabolism cages in a randomized complete block design with 3 dietary treatments of 6 pigs each based on BW and litter. Two diets were based on the 2 corns, and a P-free diet was used to measure endogenous P losses. The ATTD and STTD values of P were greater (P<0.05) in the PTC diet (71.4% and 76.9%, respectively) than those in the CC diet (27.6% and 33.4%, respectively). Pigs fed the PTC diet had a greater (P<0.05) P retention (70.7%) than those fed the CC diet (27.1%). It was concluded that PTC had a greater digestibility of energy and P than CC for growing pigs. As a consequence, if PTC replaces CC in a pig diet, the DE and ME in the diet will increase, and less inorganic P will need to be supplemented to the diet, and thus P excretion in manure will be decreased.
authors.affiliation: Department of Animal Science, Hebei Normal University of Science and Technology, Qinhuangdao 066004, China.
authors.forename: S F
authors.initials: SF
authors.lastname: Li
authors.forename: Y B
authors.initials: YB
authors.lastname: Niu
authors.forename: J S
authors.initials: JS
authors.lastname: Liu
authors.forename: L
authors.initials: L
authors.lastname: Lu
authors.forename: L Y
authors.initials: LY
authors.lastname: Zhang
authors.forename: C Y
authors.initials: CY
authors.lastname: Ran
authors.forename: M S
authors.initials: MS
authors.lastname: Feng
authors.forename: B
authors.initials: B
authors.lastname: Du
authors.forename: J L
authors.initials: JL
authors.lastname: Deng
authors.forename: X G
authors.initials: XG
authors.lastname: Luo
mesh_terms: D010832:6-Phytase / Q000235:genetics* / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism*; D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D004032:Diet / Q000662:veterinary; D004063:Digestion / Q000502:physiology; D002149:Energy Intake; D008297:Male; D010758:Phosphorus / Q000737:chemistry* / Q000378:metabolism; D030821:Plants, Genetically Modified; D013552:Swine / Q000502:physiology*; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism
chemical_list: D000596:Amino Acids; D010758:Phosphorus; D010832:6-Phytase