title: Evaluation of the order of limitation of lysine, threonine, and valine, as determined by plasma urea nitrogen, in corn-soybean meal diets of lactating sows with high body weight loss.
abstract: Three experiments were conducted to evaluate the order of limitation for Lys, Thr, and Val in corn-soybean meal diets of lactating sows experiencing high BW loss during lactation. Plasma urea N (PUN) was used as the response criterion. Experimental diets used in all 3 experiments were derived from the basal diet (BSL) formulated to 0.51% Lys using corn and soybean meal as the only sources of AA. The BSL diet was formulated by diluting a reference corn-soybean meal diet (17.2% CP, 0.90% Lys, 0.65% Thr, 0.82% Val, and 0.28% Met) with cornstarch, sucrose, and soybean oil to maintain the same ratio of corn to soybean meal. Experiment 1 was conducted to determine whether PUN is sensitive to dietary Thr and Val levels and whether a 4-d feeding period was adequate to observe a PUN response. The results demonstrated that PUN could be used as the response criterion and that a 4-d feeding period was adequate. Experiment 2 was conducted to determine whether Thr or Val was most limiting in the BSL diet. Dietary treatments used in Exp. 2 consisted of 1) BSL supplemented with 0.09% L-Lys and 0.02% DL-Met, which served as the negative control (NC2); 2) NC2 plus 0.14% L-Thr (NC2 + T); 3) NC2 plus 0.17% L-Val (NC2 + V); and 4) NC2 plus 0.14% L-Thr and 0.17% L-Val (NC2 + T + V). The value for PUN was lower for the NC2 + T and NC + T + V treatments compared with the NC2 and NC2 + V treatments (5.18 and 5.33 vs. 6.43 and 6.62; P < 0.01), indicating that Thr was most limiting in the NC2 diet. Experiment 3 was conducted to determine whether Thr or Lys was most limiting in the BSL diet. Dietary treatments used in Exp. 3 consisted of 1) the BSL diet supplemented with 0.02% DL-Met only, which served as the negative control diet (NC3); 2) the NC3 diet supplemented with 0.20% L-Lys (NC3 + L); 3) the NC3 diet supplemented with 0.14% L-Thr (NC3 + T); and 4) the NC3 diet supplemented with 0.20% L-Lys and 0.14% L-Thr (NC3 + L + T). The value for PUN was lower for NC3 + L compared with NC3 and NC3 + T (7.45 vs. 9.11 and 8.45 mg/dL; P < 0.01), and PUN for NC3 + L + T was lower than the PUN measured for NC3 + L (5.94 vs. 7.45; P < 0.01). The results of Exp. 2 and 3 indicate that Lys was first-limiting and Thr second-limiting in the BSL diet.
authors.affiliation: Department of Animal Sciences, University of Illinois, Urbana 61801, USA. ksoltwedel@scanutrition-usa.com
authors.forename: K T
authors.initials: KT
authors.lastname: Soltwedel
authors.forename: R A
authors.initials: RA
authors.lastname: Easter
authors.forename: J E
authors.initials: JE
authors.lastname: Pettigrew
mesh_terms: D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001806:Blood Urea Nitrogen; D004032:Diet / Q000662:veterinary*; D007774:Lactation; D008239:Lysine / Q000378:metabolism / Q000494:pharmacology*; D013025:Glycine max / Q000378:metabolism; D013552:Swine / Q000502:physiology*; D013912:Threonine / Q000378:metabolism / Q000494:pharmacology*; D014633:Valine / Q000378:metabolism / Q000494:pharmacology*; D015431:Weight Loss / Q000187:drug effects* / Q000502:physiology; D003313:Zea mays / Q000378:metabolism
chemical_list: D013912:Threonine; D014633:Valine; D008239:Lysine