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A total of 300 pigs (DNA 241 × 600; initial pen average BW of 6.98 ± 0.12 kg) were used in a 22 d growth trial to determine the standardized ileal digestible (SID) Lys requirement of nursery pigs from 7 to 15 kg. Pigs were weaned at approximately 21 d of age and allotted to pens based on BW and gender. There were 10 replicate pens per treatment and 6 pigs per pen. Pigs were fed a common diet for 10 d post-weaning. Pens were then randomly assigned to 1 of 6 experimental diets in a randomized complete block design based on BW. The 6 dietary treatments were formulated to 1.10, 1.20, 1.30, 1.40, 1.50, and 1.60% SID Lys by increasing the inclusion of crystalline amino acids at the expense of corn. Experimental diets were fed for 11 d. Data were analyzed using generalized linear and non-linear mixed models, fitting the data with heterogeneous residual variances as needed. Competing models included linear (LM), quadratic polynomial (QP), broken-line linear, and broken-line quadratic. For the overall treatment period, increasing SID Lys linearly improved (P<0.001) ADG and G:F, with no evidence for differences observed in ADFI (P>0.05). For ADG, the best-fitting models were LM [predicted equation: 239.95 + 124.74 × (SID Lys)] and QP [predicted equation: -321.14 + 975.22 × (SID Lys) – 315.70 × (SID Lys)2]. The maximum ADG was estimated at 1.54% (95% CI: [1.34, >1.60]%), with 99% of the maximum ADG achieved at 1.43% SID Lys in the QP model. Similarly, the best-fitting models for feed efficiency were the QP [predicted equation: 89.81 + 261.27 × (SID Lys) – 63.50 × (SID Lys)2] and the LM [predicted equation: 222.26 + 86.18 × (SID Lys)], estimating the requirement at greater than 1.60% for both models. In conclusion, the mean SID Lys required for nursery pigs from 7 to 15 kg ranged from 1.54% to at least 1.60% depending on the model and response criteria considered. Item SID Lys, % SEM 1.10 1.20 1.30 1.40 1.50 1.60 ADG, g1 365 398 397 450 425 437 13.04 ADFI, g2 542 589 559 606 573 577 18.27 G:F, g/kg3 675 676 711 744 745 759 1.59 1 ADG linear: P<0.001, quadratic: P=0.106; 2 ADFI linear: P=0.253, quadratic: P=0.183; 3 G:F linear: P<0.001, quadratic: P=0.613. [ABSTRACT FROM AUTHOR]

Our objective was to determine the effects of feeding left over finisher diet containing ractopamine HCl (RAC) and 0.82% standardized ileal digestible (SID) Lys to grower pigs of different BW at placement in the finisher. A total of 1,188 pigs (PIC 359 × 1050; initially 16.6 ± 0.16 kg) were used in a 72-d study. Pens of pigs were blocked by location and randomly allotted to 1 of 6 treatments. Treatments included three BW categories: light (12.0 ± 0.27 kg), medium (15.9 ± 0.38 kg), and heavy (21.9 ± 0.55 kg); and two dietary strategies: standard grow-finisher diets throughout (Control) or 4.5 kg/pig of a late finishing feed containing 5 mg/kg RAC and 0.82% SID Lys fed at placement and then standard diets thereafter. There were 7 pens per treatment and 27 pigs per pen. Dietary strategy, BW category, and their interaction were included as fixed effects in the statistical model and location block as a random effect. An interaction (P<0.03) between BW and diet occurred for ADG and G:F from d 0-15. Pigs fed the finisher diet with RAC had reduced ADG and G:F within all three BW categories. However, the decrease was greater in the medium BW than the other two BW categories. Pigs fed the finisher diet with RAC had reduced ADFI compared to pigs fed the control (P<0.001) from d 0-15. Overall, ADG, ADFI, and G:F differed between the BW categories (P<0.001), with heavy pigs having greater ADG and ADFI, and poorer G:F. Pigs fed the 4.5 kg/pig of finisher diet with RAC had reduced growth rate (761 vs 784 g/d; P<0.001) and feed intake (1.61 vs 1.65 kg/d; P<0.005), but no evidence for differences were observed for G:F. In conclusion, feeding a finishing diet containing ractopamine during the early stages of the grower period reduced growth performance regardless of BW category due to a decrease in feed intake compared to pigs fed standard grow-finisher diets. This demonstrates that bins holding a finisher diet containing RAC and 0.82% SID Lys should be emptied prior to placement of the next group of pigs. Item Light Medium Heavy SEM Control RAC Control RAC Control RAC d 0 to 15 ADG, g1 572d 499e 640c 544d 744a 689b 6.8 ADFI, g2 807 740 916 866 1,202 1,175 10.9 G:F, g/kg3 709c 674c 699c 628b 619b 586a 7.3 1 Diet x BW: P=0.018; 2 Diet: P<0.001, BW: P<0.001; 3 Diet x BW: P=0.026. [ABSTRACT FROM AUTHOR]

A total of 300 maternal line barrows (DNA; 200 x 400, initially 6.75 ± 0.23 kg BW) were used in a 21d trial to determine die standardized ileal digestible (SID) Lys requirement of nursery pigs from 6.8 to 15.9 kg. Pigs were randomly allotted to pens at weaning based on B W and were fed a common diet for 9 d after weaning. There were 10 replicate pens/treatment and 5 pigs/pen. Pens of pigs were allotted to experimental diets based on average BW, in a completely randomized design. The 6 dietary treatments consisted of 1.05, 1.15, 1.25, 1.35, 1.45, and 1.55% SID Lys and were achieved by increasing the inclusion of crystalline amino acids, allowing soybean-meal to stay constant across dietary treatments. Experimental data was analyzed using general linear and nonlinear mixed models with heterogeneous residual variances and pen as the experimental unit. Competing models included linear (LM), quadratic polynomial (QP), broken-line linear (BLL), and broken-line quadratic (BLQ). The best-fitting model for each response was selected using Bayesian information criterion (BIC). Increasing SID Lys linearly improved (P = 0.001) G:F. There was a marginal quadratic response for ADG (P = 0.067) with increasing SID Lys. The ADFI increased in a quadratic manner (P = 0.019) from 1.05 to 1.25% SID Lys. For ADG, die best-fitting comparable models were BLL [predicted equation: 462- 271 x (1.29- Lys), if SID Lys < 1.29%] and BLQ [predicted equation: 465- 372 x (1.47- Lys)2, if SID Lys < 1.47%], estimating the requirement at 1.29% (95% CI: [1.23, 1.35]%) and 1.47% (95% CI: [1.31, > 1.55]%), respectively. For G:F, the best-fitting models were QP [predicted equation: 0.750- 0.317 x (Lys) + 0.214 x (Lys)2] and LM [predicted equation: 0.392 + 0.241 x (Lys)], estimating the requirement at greater than 1.55% for both models. In conclusion, the estimated mean SID Lys required for nursery pigs from 6.8 to 15.9 kg ranged from 1.29% for maximum ADG to at least 1.55% for maximum G:F [ABSTRACT FROM AUTHOR]