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Experiments (Exp.) were conducted with Cornish Rock males (4 to 14 or 15 d of age) to determine the Lys requirement (Exp. 1) and the optimum ratio of TSAA:Lys for chicks fed adequate or inadequate Lys (Exp. 2). In Exp. 1, 180 chicks were allotted on the basis of BW to six treatments with six replications of five chicks each in a completely randomized design (CRD). Average initial and final BW were 73.5 and 415.5 g. The Lys levels fed were: 0.8, 0.9, 1.0, 1.1, 1.2, and 1.3% digestible Lys. In Exp. 2, 240 chicks were allotted on the basis of BW to 12 treatments with four replications of five chicks each in a CRD. Average initial and final BW were 68.5 and 336.3 g. Chicks were fed either 0.82 or 1.0% digestible Lys and within each Lys level, a ratio of TSAA:Lys of: 0.55, 0.63, 0.72, 0.80, 0.88, and 0.96, resulting in a 2 x 6 factorial arrangement of treatments. At the end of each trial, all chicks were weighed and pen feed consumption was measured. In Exp. 1, average daily gain (ADG) and gain:feed (GF) increased (linear, P < 0.01; quadratic, P < 0.02) as dietary Lys increased. A cubic (P < 0.04) effect of Lys for average daily feed intake (ADFI) was observed. One-slope, broken-line regression models estimated Lys requirements of 1.0, 0.9, and 1.1% for ADG, ADFI, and GF, respectively. In Exp. 2, chicks fed 1.0% Lys had higher (P < 0.01) ADG, ADFI, and GF than chicks fed 0.82% Lys. Daily gain, ADFI, and GF increased (linear, P < 0.01; quadratic, P < 0.01) as TSAA:Lys increased. For ADG, ADFI, and GF, one-slope, broken-line regression models estimated required ratios of TSAA:Lys of 0.66, 0.71, and 0.63 for chicks fed 1.0% Lys and 0.66, 0.67, and 0.63 for chicks fed 0.82% Lys. There were no differences (P > 0.05) in the estimated ratios of TSAA:Lys required to maximize ADG, ADFI, and GF for chicks fed 0.82 and 1.0% Lys. Thus, similar ratios of an indispensable amino acid to Lys can be obtained when chicks are fed at or slightly below their Lys requirement.
Experiments (Exp.) were conducted with Cornish Rock males (4 to 14 or 15 d of age) to determine the Lys requirement (Exp. 1) and the optimum ratio of TSAA:Lys for chicks fed adequate or inadequate Lys (Exp. 2). In Exp. 1, 180 chicks were allotted on the basis of BW to six treatments with six replications of five chicks each in a completely randomized design (CRD). Average initial and final BW were 73.5 and 415.5 g. The Lys levels fed were: 0.8, 0.9, 1.0, 1.1, 1.2, and 1.3% digestible Lys. In Exp. 2, 240 chicks were allotted on the basis of BW to 12 treatments with four replications of five chicks each in a CRD. Average initial and final BW were 68.5 and 336.3 g. Chicks were fed either 0.82 or 1.0% digestible Lys and within each Lys level, a ratio of TSAA:Lys of: 0.55, 0.63, 0.72, 0.80, 0.88, and 0.96, resulting in a 2 x 6 factorial arrangement of treatments. At the end of each trial, all chicks were weighed and pen feed consumption was measured. In Exp. 1, average daily gain (ADG) and gain:feed (GF) increased (linear, P < 0.01; quadratic, P < 0.02) as dietary Lys increased. A cubic (P < 0.04) effect of Lys for average daily feed intake (ADFI) was observed. One-slope, broken-line regression models estimated Lys requirements of 1.0, 0.9, and 1.1% for ADG, ADFI, and GF, respectively. In Exp. 2, chicks fed 1.0% Lys had higher (P < 0.01) ADG, ADFI, and GF than chicks fed 0.82% Lys. Daily gain, ADFI, and GF increased (linear, P < 0.01; quadratic, P < 0.01) as TSAA:Lys increased. For ADG, ADFI, and GF, one-slope, broken-line regression models estimated required ratios of TSAA:Lys of 0.66, 0.71, and 0.63 for chicks fed 1.0% Lys and 0.66, 0.67, and 0.63 for chicks fed 0.82% Lys. There were no differences (P > 0.05) in the estimated ratios of TSAA:Lys required to maximize ADG, ADFI, and GF for chicks fed 0.82 and 1.0% Lys. Thus, similar ratios of an indispensable amino acid to Lys can be obtained when chicks are fed at or slightly below their Lys requirement.
The objective of this study was to evaluate the relative bioavailability (RBV) of l-Lys sulfate in comparison to l-Lys HCl based on the growth performance response from approximately 26 to 48 kg and from approximately 68 to 114 kg. The effect of Lys source on blood urea nitrogen (BUN), digestibility of dry matter (DM) and sulfur (S), as well as carcass characteristics was determined. A total of 280 growing pigs (25.9 ± 0.25 kg BW) were randomly assigned to one of seven dietary treatments in 56 pens, with five pigs per pen. The diets included a Lys-deficient basal diet (65% of requirement) and the basal diet supplemented with three graded levels of Lys (75%, 85%, and 95% of requirement), as either l-Lys HCl (78.8% Lys purity) or l-Lys sulfate (54.6% Lys purity). The experiment lasted for 112 d, with four dietary phases: Phase 1 lasted for 4 wk (BW: 25.9 to 47.5 kg), Phase 2 lasted for 3 wk (common commercial diet as washout period), Phase 3 lasted for 5 wk (BW: 67.5 to 98.2 kg), and Phase 4 lasted for 3 or 4 wk to reach an average market weight of 114.2 kg. Fresh fecal samples of pigs fed the highest levels of Lys (both Lys sources) were collected on 7 to 10 days after the beginning of Phase 3 for digestibility assay. Blood samples were collected on day 21 and day 81 to determine BUN. Carcass data were collected at a commercial packing plant. Data were analyzed using PROC GLM of SAS (9.4) according to a completely randomized design with pen as the experimental unit. The RBV of l-Lys sulfate was determined using the multiple regression slope-ratio method. Increasing levels of Lys, independent of source, increased (P < 0.05) BW, ADG, and feed efficiency during Phases 1, 3, and 4; market BW increased linearly (P < 0.01) and backfat and BUN decreased linearly (P < 0.01). Lysine source had no impact on growth performance, carcass characteristics, BUN, or digestibility of S and DM. The RBV of l-Lys sulfate compared with l-Lys HCl was also not different based upon ADG or G:F during Phase 1, 3, or 4. These data suggest that the bioavailability of Lys in l-Lys sulfate and l-Lys HCl is at least equivalent for growing–finishing pigs.
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