| The objectives of this research are: (1) evaluate the effects of supplemental amino acids (AA) in low crude protein (CP) diet with varying tryptophan (Trp) levels on growth performance, gut health, and AA transporters when compared to conventional high CP diets, (2) evaluate bioefficacy of liquid L-Lys in comparison to crystalline L-Lys HCl on growth performance of growing pigs, and (3) evaluate functional difference of liquid based L-Lys and crystalline L-Lys HCl on the growth performance, intestinal health, and intestinal integrity in newly weaned pigs.;Experiment 1 (Chapter 2) investigated effects of supplemental AA on growing pigs fed low protein diets with varying Trp levels. Tryptophan is an essential amino acid and is considered as 4th limiting amino acids in swine diets. However, tryptophan to lysine ratio in low crude protein diets have been suggested differently. A total of 90 pigs were allotted into 3 dietary treatments. Treatments were (1) negative control diet (NC: diet containing 18% CP with supplemental Lys, Met, and Thr), (2) positive control diet (PC: diet containing 16% CP supplemental Lys, Met, Thr and Trp), and (3) positive control diet supplemented with extra tryptophan (PCT: PC + 0.05% Trp). Collectively, use of supplemental amino acids (Lys, Met, Thr, and Trp) in low CP diet and 0.05% additional Trp increased BW after wean, intestinal development and AA transporters in jejunum. Moreover, additional 0.05% Trp exceeding the NRC 2012 requirements enhanced intestinal tight junction proteins.;Experiment 2 (Chapter 3) evaluated the effects of liquid L-Lys supplementation on growth performance in growing-finishing pigs compared with crystalline L-Lys HCl. Liquid L-Lys contains free form of lysine; however, it contains lower lysine content based on the product specification. Hence, these L-Lys products probably have different bioefficacy when they are supplemented in pig diets. In Exp. 1, A total of hundred and twenty six pigs were randomly allotted to 7 dietary treatments which were, CON: a control diet without supplemental Lys meeting 75% of SID Lys requirement, Level 1 diets with crystalline L-Lys HCl (C1) or liquid L-Lys (L1) meeting 82% of SID Lys requirement, Level 2 (C2 or L2) diets meeting 89% of SID-Lys requirement and Level 3 (C3 or L3) diets meeting 96% of SID Lys requirement. In Exp. 2, seventy two pigs in L2, L3, C2, and C3 were fed diets with 0.9% SID lysine and 6.75 mg/kg of ractopamine (Elanco, IN., USA) for 3 weeks. Collectively, these studies indicated that both L-Lys HCl and liquid L-Lys successfully provided needed lysine as shown in improve growth performance and there were no difference in bioefficacy between two sources of supplemental L-Lys.;Experiment 3 (Chapter 4) evaluated functional difference of liquid based L-Lys and crystalline L-Lys HCl on the growth performance, intestinal health, and intestinal integrity in newly weaned pigs. Twenty four newly weaned pigs were randomly allotted to 2 dietary treatments. Two treatments were, (1) a diet supplemented with crystalline L-Lys HCl or (2) a diet supplemented with liquid based L-Lys. Collectively, this study indicates that liquid LLys supplementation improved intestinal health potentially by decreasing of systemic inflammatory status and improving jejunal morphology compared with the use of crystalline L-Lys HCl in newly weaned pigs. |
