title: Difference in rates of net portal absorption between crystalline and protein-bound lysine and threonine in growing pigs fed once daily.
abstract: Net portal absorption of AA during the 6-h postprandial period was measured in eight gilts (48.5 +/- 1.6 kg BW) in a crossover design. The pigs had chronic catheters placed in the portal vein, carotid artery, and ileal vein, and were trained to consume 1.2 kg of a standard grower diet once daily. Blood samples were taken every 30 min for 4 h and then hourly until 6 h after feeding. The first set of blood samples was taken after pigs were fed a meal of the test 16% CP corn-soybean meal diet (16% CP) or the test 12% CP corn-soybean meal diet supplemented with crystalline lysine, threonine, and tryptophan (12% CP + AA) to equal the three AA levels in the 16% CP diet. Pigs were then fed the standard diet for 2 d. Following that, blood samples were again taken after the pigs were fed a meal of the test diet that was not given to them at the first sampling period. Net portal AA absorption was calculated by multiplying porto-arterial plasma AA concentration difference by portal vein plasma flow rate (PVPF), estimated by an indicator-dilution technique employing p-aminohippuric acid as the indicator infused into the ileal vein. Plasma concentrations of lysine and threonine of pigs were affected by the diet x time interaction (P < 0.01). Portal and arterial plasma lysine and threonine concentrations in pigs attained the maximal level by 1 h postprandial when the 12% CP + AA diet was fed, but reached the peak level at 2.5 h postprandial when the 16% CP diet was given. The PVPF of pigs over the 6 h postprandial was less (P < 0.01) when the 12% CP + AA diet was given than when the 16% CP diet was fed. Net portal absorptions of lysine and threonine also were affected (P < 0.05) by time x diet interaction. The peak portal absorption of both lysine and threonine in pigs appeared at 0.5 h postprandial when the 12% CP + AA diet was given, but at 2.5 h postprandial with the feeding of the 16% CP diet. The early appearance of peak portal absorption of lysine and threonine from feeding the 12% CP + AA compared with the 16% CP diet indicates that crystalline lysine and threonine are absorbed more rapidly than protein-bound lysine and threonine in pigs fed once daily.
authors.affiliation: ARS, USDA, U.S. Meat Animal Research Center, Clay Center, NE 68933, USA. jtyen@email.marc.usda.gov
authors.forename: J T
authors.initials: JT
authors.lastname: Yen
authors.forename: B J
authors.initials: BJ
authors.lastname: Kerr
authors.forename: R A
authors.initials: RA
authors.lastname: Easter
authors.forename: A M
authors.initials: AM
authors.lastname: Parkhurst
mesh_terms: D000042:Absorption; D000818:Animals; D002339:Carotid Arteries / Q000502:physiology*; D018592:Cross-Over Studies; D003460:Crystallization; D005260:Female; D007082:Ileum / Q000098:blood supply; D008239:Lysine / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics*; D011169:Portal Vein / Q000502:physiology*; D019518:Postprandial Period; D011897:Random Allocation; D012039:Regional Blood Flow; D013552:Swine / Q000378:metabolism*; D013912:Threonine / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics*; D014680:Veins / Q000502:physiology
chemical_list: D013912:Threonine; D008239:Lysine