title: The appropriate standardized ileal digestible tryptophan to lysine ratio improves pig performance and regulates hormones and muscular amino acid transporters in late finishing gilts fed low-protein diets.
abstract: This study investigated the effects of various standardized ileal digestible (SID) Trp to Lys ratios on the performance and carcass characteristics of late finishing gilts receiving low-CP (9.6%) diets supplemented with crystalline AA. Ninety gilts (89.1 ± 5.1 kg) were used in a dose-response study conducted for 35 d. Crystalline Trp (0, 0.1, 0.2, 0.4, or 0.6 g/kg) was added to a corn-wheat bran basal diet providing SID Trp to Lys ratios of 0.12, 0.15, 0.18, 0.21, or 0.24. Each diet was fed to 6 pens of pigs with 3 gilts per pen. At the end of the experiment, 30 gilts (1 pig per pen) were slaughtered to evaluate carcass traits and meat quality (BW = 121 kg). Increasing the SID Trp to Lys ratio increased ADG (linear and quadratic effect, < 0.05) and also improved G:F (linear and quadratic effect, < 0.05). Serum urea nitrogen (SUN) decreased as the SID Trp to Lys ratio increased (linear and quadratic effects, < 0.05). A quadratic effect of L* light and marbling in the longissimus dorsi was observed as the dietary SID Trp to Lys ratio increased ( < 0.05). Increasing the SID Trp to Lys ratio increased the level of serum GH (quadratic effect, < 0.05) and also increased the level of serum IGF-1 (linear and quadratic effect, < 0.05). Increasing the SID Trp to Lys ratio increased the protein abundance of the muscular AA transporter of sodium-coupled neutral amino acid transporter 2 (SNAT2) in the longissimus dorsi muscle (linear and quadratic effect, < 0.05). The optimum SID Trp to Lys ratios to maximize ADG and G:F as well as to minimize SUN levels were 0.16, 0.17, and 0.16 using a linear-breakpoint model and 0.20, 0.20, and 0.20 using a quadratic model. Tryptophan could influence serum GH and IGF-1 secretion and protein abundance of the muscular AA transporter of SNAT2 in the longissimus dorsi muscle in late finishing gilts fed low-protein diets.
authors.forename: W F
authors.initials: WF
authors.lastname: Ma
authors.forename: S H
authors.initials: SH
authors.lastname: Zhang
authors.forename: X F
authors.initials: XF
authors.lastname: Zeng
authors.forename: X T
authors.initials: XT
authors.lastname: Liu
authors.forename: C Y
authors.initials: CY
authors.lastname: Xie
authors.forename: G J
authors.initials: GJ
authors.lastname: Zhang
authors.forename: S Y
authors.initials: SY
authors.lastname: Qiao
mesh_terms: D026905:Amino Acid Transport Systems / Q000187:drug effects / Q000378:metabolism; D000821:Animal Feed / Q000032:analysis; D000822:Animal Husbandry / Q000379:methods; D000824:Animal Nutritional Physiological Phenomena / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001806:Blood Urea Nitrogen; D018753:Diet, Protein-Restricted / Q000592:standards / Q000662:veterinary*; D019587:Dietary Supplements / Q000592:standards; D005260:Female; D013006:Growth Hormone / Q000097:blood / Q000187:drug effects; D007082:Ileum / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000187:drug effects / Q000378:metabolism; D008239:Lysine / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D013552:Swine / Q000254:growth & development* / Q000378:metabolism; D014364:Tryptophan / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D026905:Amino Acid Transport Systems; D007334:Insulin-Like Growth Factor I; D014364:Tryptophan; D013006:Growth Hormone; D008239:Lysine