Standardized Ileal Digestible Lys Research Articles

141 Determination of the optimum standardized ileal digestible lysine for nursery pigs fed high levels of dietary fiber

Abstract An experiment was conducted to determine the optimum standardized ileal digestible (SID) Lys for nursery swine-fed high levels of dietary fiber. A total of 2,525 pigs [PIC 337 × 1050, initial body weight (BW) = 6.5 kg], placed in pens of 36 mixed-sex pigs, were used in a 42-d trial. Pigs were allotted to 1 of 5 dietary treatments with 14 replicates per treatment. Increasing dietary SID Lys concentrations of 1.14, 1.22, 1.30, 1.38, and 1.45% were obtained by blending the 1.14% and the 1.45% SID Lys diets via Big Dutchman DryExact Pro feeding system (Big Dutchman, Holland, MI). The different SID Lys levels were obtained by changing the inclusion rate of soybean meal, which ranged from 15 to 28%. The experimental diets contained sugar beet pulp and soy hulls, resulting in an NDF level of 10.5%. Experimental diets were fed for 17 d and followed by a common corn, soybean meal, and 10% DDGS diet with 1.30% SID Lys from d 17 to 42. Pigs were weighed on d 0, 17, and 42 to calculate average daily gain (ADG), average daily feed intake (ADFI) and gain to feed ratio (G:F). From d 0 to 17, a quadratic (P < 0.05) improvement in ADG and ADFI was observed for pigs fed increasing SID Lys up to 1.38%, plateauing thereafter. Pigs fed increasing SID Lys had linearly (P = 0.001) improved G:F (Table 1). From d 17 to 42, there was no evidence (P > 0.10) for differences in ADG, yet ADFI increased linearly (P = 0.004) while G:F decreased linearly (P = 0.001) for pigs previously fed increasing concentrations of SID Lys. Overall (d 0 to 42) for pigs fed increasing SID Lys, ADG and ADFI increased quadratically (P < 0.05) up to 1.38% SID Lys, whereas G:F increased linearly (P = 0.001) up to 1.45% SID Lys. Mortality and removal rate was quadratically influenced (P < 0.05) by feeding increasing SID Lys. Our findings suggest feeding weaned pigs from d 0 to 17 a diet containing 1.38% SID Lys is optimal for growth performance while minimizing mortality and removal rate.

25 Effects of dietary standardized ileal digestible lysine on growth performance, carcass characteristics, and economics of pigs from 100 to 130 kg

Abstract A total of 1,570 finishing pigs (337 × 1050, PIC; initially 103.4 ± 0.85 kg) were used in a 28-d trial to determine the effects of feeding increasing standardized ileal digestible (SID) Lys to pigs between 100 to 130 kg on growth performance, carcass characteristics, and economics. Before the beginning of the study, the 3 heaviest pigs per pen were removed and marketed with all remaining pigs marketed 28-d later at the end of the study. Pigs were housed in mixed sex pens, with 20 pigs per pen and 20 pens per treatment. The experiment was a randomized complete block design with four dietary treatments: 0.63, 0.68, 0.75, and 0.82% SID Lys. Diets were corn-soybean meal-based and fed in meal form. Dietary treatments were similar in NE and increasing SID Lys was achieved by increasing soybean meal and feed grade amino acids. For the first 14 d from 100 to approximately 118 kg, there was a linear tendency for increased (P = 0.074) average daily gain (ADG), a linear improvement (P < 0.05) in gain to feed ratio (G:F), and increase (P < 0.001) in SID lysine intake per kg of gain as SID Lys increased (Table). For the second 14 d from 118 to 128 kg, SID Lys intake per kg of gain increased (P < 0.001) as SID Lys increased, however; there was no evidence for difference (P > 0.10) for any growth performance traits. Overall, there was a linear increase (P = 0.018) in G:F and increase (P < 0.001) in SID lysine intake per kg of gain as SID Lys increased. Increasing SID Lys also linearly increased (P < 0.05) percentage lean and decreased (P < 0.05) backfat depth with no evidence for differences (P > 0.10) in other carcass criteria. For economics, feed cost and feed cost per kg of gain linearly increased (P < 0.05) as SID Lys increased in both low and high-price scenarios. Income over feed cost linearly decreased (P < 0.05) as dietary SID Lys increased in a low-price scenario, but there was no difference between treatments in a high-price scenario (P > 0.10). In conclusion, increasing dietary SID lysine in the last 28-d of the finisher period linearly increased G:F and SID Lys intake per kg of gain without significantly influencing other growth performance traits. Feed cost per kg of gain was linearly increased for both low and high-price scenarios with a detriment for IOFC with increasing SID Lys in the low-price scenario.

11 The effect of increased standardized ileal digestible lysine through increased soybean meal during late gestation on lactating sow and litter performance

Abstract A total of 87 sows (Line 241, DNA) and their offspring were used to evaluate the effect of increasing standardized ileal digestible (SID) lysine through increasing soybean meal (SBM) concentration in late gestation diets on lactating sow and litter performance. Sows were blocked by parity and body weight (BW) on approximately d 90 of gestation and allotted to 1 of 3 treatments with 29 replications per treatment. Diets included increasing SID lysine (0.60, 0.80, or 1.00%) through increased SBM (14, 21, or 29% of the diet). Sows received approximately 2.04 kg/d of their treatment diet for an average SID Lys intake of 11.9, 15.8, or 19.9 g/d, respectively. Diets were fed from d 90 of gestation until farrowing. After farrowing, all females were fed a common lactation diet containing 1.10% SID Lys until weaning (19 d post-farrow). Sow BW, caliper score, and backfat and loin depth were collected on d 90, upon entry into the farrowing house (d 110), and at weaning. Urine samples were collected on d 90 and 110 of gestation to ascertain urinary creatinine concentrations. Litters were cross-fostered within sow treatment by 48 h after farrowing to equalize litter size. Parity was included in the statistical model as a fixed effect with females being classified as either a primiparous (n = 35) or multiparous (n = 52) sow. Body weight gain from d 90 to 110 of gestation increased as SID Lys increased (linear, P < 0.001; Table). There were no differences in starting litter size or piglet birth weight with increasing SID Lys in late gestation (linear, P > 0.10). Change in urinary creatinine level from d 90 to 110 of gestation tended to decrease as SID Lys increased in the diet (linear, P = 0.063) suggesting that less muscle catabolism occurred with increasing SID Lys. Piglet average daily gain (ADG) from d 2 to 10 of lactation linearly increased as SID Lys increased (P = 0.017), but not from d 2 to weaning. From d 2 until weaning, litters from sows fed the 0.80% SID Lys gestation diet had the greatest litter gain (quadratic, P = 0.044). Pre-weaning mortality from birth until d 2 of lactation was greatest for sows fed 0.80% SID Lys (quadratic, P = 0.025). There was a parity × gestation diet interaction for pre-weaning mortality from d 2 to weaning (P = 0.049) where mortality increased as SID Lys increased in primiparous sows but decreased in multiparous sows. In conclusion, increased SID Lys through increased SBM linearly increased late gestation sow BW gain and piglet ADG during the first portion of lactation. However, litters from sows on the 0.80% SID Lys treatment exhibited the highest litter ADG during late lactation and overall.

274 Socialization of piglets during suckling enhanced feed intake after weaning but did not alter their response to dietary amino acid concentration

Abstract The present study hypothesized that pre-weaning socialized piglets would reduce damaging behavior and when fed an increased dietary standardized ileal digestible (SID) Lys (and amino acids) to net energy (NE) ratio post-weaning would increase early post weaning feed intake (FI) and growth performance, and in nursery pigs. Socializing included two groups of five sows and their litters for which farrowing pen walls were removed allowing piglets to co-mingle for 10 d before weaning (S) whereas traditionally housed piglets pertained to housing a single sow with her litter (T; n = 15). At weaning, 120 mixed-gender piglets [7.2 ± 0.7 kg body weight (BW)] were allocated based on litter origin, sow parity, and piglet BW to 12 pens equipped with single-space electronic feeding stations with 10 pigs/pen for a 41-d study. In this 2 × 2 factorial arrangement, factors were litter background (socialized vs. traditional) and dietary SID Lys: NE (High 1.32 vs. Low 1.15 SID Lys:NE MJ/kg). Daily individual FI and BW and skin injuries at different timepoints after weaning were determined. Wheat-barley based diets were isoenergetic (10.6 MJ/kg) and offered in two phases (i.e., d 0-14 and d 14-41). The day after weaning, socializing reduced the proportion of piglets with more than five skin injuries from 45.7% to 3.0% compared with traditional housing (P < 0.05). Early post-weaning, daily FI was 50% greater for S-LowLys:NE pigs than S-HighLys:NE on d1, then, T-LowLys:NE was greatest (~25% above other treatments) during d 3-6 (all P < 0.05). The trend maintained during d 6-8 with T-LowLys:NE and S-HighLys:NE being similar each other (P > 0.05). The average number of visits per day during the first 10 d was greater (P < 0.01) for S-HighLys:NE and T-LowLys:NE (33 visits each) compared with T-HighLys:NE (24 visits). Overall, S-HighLys:NE pigs tended (P < 0.10) to have a greater end BW (23.8 vs. 22.1 kg) and a greater d 0-41 average daily gain (ADG) than T-HighLys:NE (530 vs. 472 g/d). For d22-29, the average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (FE), were greater for S-HighLys:NE and T-LowLys:NE compared with S-LowLys:NE and T-HighLys:NE (P < 0.05). No other meaningful interactions were observed between socializing and Lys:NE on growth performance. However, looking at main factors, socializing increased ADG during d 29-41 by 9% (P = 0.01) coinciding with a 4% greater FE (P = 0.09). The data suggest that traditionally housed piglets fed a HighLys:NE diet post-weaning had lower daily FI and growth performance compared with T-LowLys:NE and socialized piglets irrespective of the Lys:NE contrast. In conclusion, the present study led to a better understanding of nutritional requirements and FI in situations with different pre-weaning housing schemes of piglets. In the present conditions, pre-weaning socialization of pigs may stimulate feed intake earlier post-weaning and allow a better transition independently from the Lys (and amino acid) to NE ratio.

143 Effect of increasing dietary net energy content at a constant lysine on feed intake and performance of 7 to 11 kg and 11 to 20 kg pigs

Abstract Information about NE requirements for nursery pigs is still limited. Therefore, 2 experiments were conducted to evaluate the effect of dietary NE contents on growth performance of 7 to 11 kg pigs (Exp. 1) and 11 to 20 kg pigs (Exp. 2). In Exp. 1, mixed-sex pigs (n = 192; PIC; initial body weight (BW) of 7.8 ± 1.07 kg] were assigned to 4 diets for 14 d. Diets 1 to 4 were formulated to contain 4 levels of NE (9.8, 10.1, 10.4 and 10.7 MJ/kg) and adequate in all AA with standardized ileal digestible (SID) Lys being constant at 1.42%. In Exp. 2, mixed-sex pigs (n = 192; PIC; initial BW of 11.2 ± 1.54 kg) were assigned to 4 diets for 21 d. Diets 1 to 4 contained 4 levels of NE (9.6, 9.9, 10.2 and 10.5 MJ/kg) and adequate in all AA (1.32% SID Lys). For both studies, there were 6 pen replicates (4 entire males and 4 gilts/pen) per treatment, and diets were based on corn, soybean meal, whey powder, wheat bran and soy oil. Pigs had ad libitum access to feed (mash) and water. Individual pigs and pen feed disappearance were weighed weekly to calculate average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency gain to feed ratio (G:F). Data were analyzed by ANOVA using the GLM procedure of SAS with pen as the experimental unit. In Exp. 1, ADFI tended to decrease (quadratic; P ≤ 0.08) with increasing NE levels during d 0 to 7 and d 8 to 14. The ADG during d 0 to 7 tended to be greater (158, 192, 187 and 152 g for diets 1 to 4; quadratic; P = 0.08) at 10.1 MJ/kg NE; however, the overall ADG (d 0 to 14) was not affected by the NE levels. Although not significant, G:F, Lys utilization efficiency were greatest at 10.1 MJ/kg NE for the overall period. In Exp. 2, ADFI decreased (827, 783, 768 and 749 g for diets 1 to 4; linear; P = 0.05) with increasing NE levels during d 15 to 21 but was not affected (P > 0.05) for other periods. The ADG (d 8 to 14) tended to be greater at 9.6 MJ/kg NE (quadratic; P = 0.06) and G:F (d 15 to 21) tended to be greater at a dietary NE of 10.2 MJ/kg (linear; P = 0.10). However, the overall (d 0 to 21) ADG and G:F were not affected (P > 0.05) by NE levels. Although not significant, G:F and Lys utilization efficiency were greatest at a dietary NE of 10.2 MJ/kg for the overall period. These results indicate that G:F of 7 to 11 kg pigs and 11 to 20 kg pigs maximized at a dietary NE content of 10.1 MJ/kg and 10.2 MJ/kg, which correspond to 1.41 and 1.29 g SID Lys/MJ NE, respectively.

14 Effects of increasing daily dietary standardized ileal digestible lysine intake of gilts and sows during d 35 to 112 of gestation on reproductive performance

Abstract Our objective was to determine the effects of increasing daily dietary standardized ileal digestible (SID) lysine (Lys) intake during d 35 to 112 of gestation on sow and litter performance. A total of 704 gilts and sows (PIC Camborough) were used. Females were group-housed after d 35 of gestation and individually fed with electronic sow feeders (ESF). At d 35 of gestation, females were balanced for body weight (BW) and caliper scores within parity categories, and randomly allotted to 1 of 4 treatments. Treatments consisted of increasing daily dietary SID Lys intake (11.1, 13.5, 16.1, and 18.5 g/d). Both gilts and sows received 2.37 kg/d of a gestation diet containing 3.17 Mcal of ME/kg, which was estimated to avoid feeding females below their maintenance requirements throughout the entire gestation. Treatments were achieved by different blend of low (0.47% SID Lys) and high (0.78% SID Lys) Lys diets via ESF based on the set feed allowance for females. Sow was the experimental unit and data were analyzed using generalized linear mixed models with the lmer and glmerfunctions of R, considering treatment, parity, and their interaction as fixed effects. There was no evidence (P > 0.10) of treatment and parity interaction for any response criteria. Body weight at d 112 of gestation and BW change from d 35 to 112 of gestation increased (linear; P < 0.05) with increasing daily dietary SID Lys intake (Table 1). No evidence for SID Lys treatment differences were observed for BW at weaning or BW change during lactation (P > 0.10). There was no evidence (P > 0.10) for treatment differences on caliper score (CS) at d 35 of gestation, d 112 of gestation, at weaning, or CS changes during gestation and lactation. There was no evidence for treatment difference on total born, percentage stillbirth and percentage of mummified fetuses (P > 0.10). However, there was a marginal reduction in percentage born alive piglets (quadratic, P = 0.056), with the least proportion of piglets born alive observed in females receiving 16.1g of daily SID Lys intake from d35 to d112 of gestation. Increasing daily dietary SID Lys intake during d 35 to 112 of gestation did not affect piglet birth weight, piglet average daily gain during lactation, proportion of removed pigs, and proportion of dead pigs during lactation. In summary, increasing daily dietary SID Lys intake during d35-to-112 of gestation increased female BW; however, no evidence of benefits was observed for female reproductive performance and litter performance during lactation.

31 Effects of dietary standardized ileal digestible (SID) lysine (Lys) levels and dietary SID tryptophan to Lys ratios on growth performance and behavior of late-nursery to finish maternal barrows

Abstract The objective was to determine the effects of dietary standardized ileal digestible (SID) lysine (Lys) levels and SID tryptophan (Trp) to Lys ratios on growth performance and behavior of late-nursery to finish maternal barrows. A total of 2,293 barrows (PIC Camborough, initially 11.9 ± 0.35 kg) were used in this trial with 96 mixed-sex pens and 23 to 25 pigs/pen. There was a total of 6 dietary phases: P1:11.9-29.5 kg; P2:29.5-49.6 kg; P3:49.6-62.6 kg; P4:62.6-80.3 kg; P5:80.3-103.3 kg; and P6:103.3-137.8 kg. Pens were blocked by body weight and randomly allotted to 1 of 6 treatments:T1: 100% Lys (dietary SID Lys levels meet PIC SID Lys recommendation) and 21.0% of SID Trp:Lys ratio; T2: 100% Lys and 18.5% of SID Trp:Lys ratio; T3: 100% Lys and 16.0% of SID Trp:Lys ratio; T4: 80% Lys (dietary SID Lys levels meet 80% of PIC SID Lys recommendation) and 21.0% of SID Trp:Lys ratio; T5: 80% Lys and 18.5% of SID Trp:Lys ratio; and T6: 80% Lys and 16.0% of SID Trp:Lys ratio for P1-P2 and then 100% Lys and 18.5% of SID Trp:Lys ratio for P3-P6. Ear lesion (EL) was monitored during P2-P5. Data were analyzed using a linear mixed model in R Studio (Version 3.5.2, R Core Team; Vienna, Austria). Pigs fed T1 and T2 showed improved average daily gain than T6 (P < 0.05), with other treatments intermediate (Table 1). Pigs fed T2 showed improved average daily feed intake as compared with T6 (P < 0.05), with other treatments intermediate. There was no evidence for significant difference on feed-to-gain ratio or mortality. Removal was significantly greater for pigs fed T6 compared with all other treatments (P < 0.05). Pigs fed T2 had significantly greater hot carcass weight than T4, with other treatments intermediate. There was no evidence for significant differences on carcass yield or lean percentage. Pig fed T6 had significantly greater incidence of EL in P2 than all other treatments (P < 0.05). Pigs fed T4 and T6 had greater incidence of EL in P3 than T1 (P < 0.05), with other treatments intermediate. Pigs fed T5 and T6 had significantly greater incidence of EL in P4 than T1, T2, and T3 (P < 0.05), with T4 intermediate. During P5, pigs fed T4 and T5 had the greatest incidence of EL (P < 0.05), while pigs fed T6 had significant greater incidence of EL than T3 (P < 0.05), with T1 and T2 intermediate. In conclusion, dietary SID Lys and SID Trp:Lys ratio less than PIC recommendation during late-nursery-to-grower phase resulted in compromised overall growth performance of maternal barrows, even with restored dietary SID Lys and SID Trp:Lys levels in finish phase. Dietary SID Lys level and/or SID Trp:Lys ratios lower than PIC recommendation may result in greater incidence of aggression behavior in maternal barrows.

95 Effects of increasing standardized ileal digestible valine:lysine ratio on growth performance in finishing pigs

Abstract Two experiments evaluated the effects of increasing standardized ileal digestible (SID) Val:Lys ratio on the growth performance of 38 to 67 kg (Exp. 1) and 90 to 116 kg (Exp. 2) finishing pigs. In Exp. 1, pigs (n = 647; DNA 600 × 241) were randomly allotted to 1 of 6 dietary treatments with 8 or 9 pigs per pen and 12 replications per treatment. Diets were corn-soybean meal-based, and low and high Val diets were manufactured and blended to create intermediate Val:Lys ratio diets. Diets were formulated to contain 0.90% SID Lys, and treatments consisted of SID Val:Lys ratios of 60%, 63%, 66%, 69%, 72%, and 75%. At the conclusion of the 27-d study, all pigs were fed a common diet for 30 d and then randomly re-allotted to 1 of 6 diets formulated to contain 0.65% SID Lys and SID Val:Lys ratios of 63%, 66%, 69%, 72%, 75%, and 78% (Exp. 2). In both experiments blood samples were collected from 3 pigs per pen on d 15 for plasma urea nitrogen (PUN) analysis. In Exp. 1, final body weight (BW), average daily gain (ADG), and average daily feed intake (ADFI) increased (quadratic, P < 0.05) as Val:Lys increased (Table). Pigs fed the diet with 66% SID Val:Lys ratio had the greatest ADG, whereas pigs fed 72% SID Val:Lys ratio had the greatest ADFI. As the Val:Lys ratio increased, gain to feed ratio (G:F) decreased (linear, P < 0.05). Valine and Lys intake increased (quadratic, P < 0.05) as the Val:Lys ratio increased with the greatest intake observed at 72% SID Val:Lys. Valine and Lys intake per kg of gain increased (linear, P < 0.05) as the level of Val in the diet increased. Plasma urea nitrogen decreased (linear, P < 0.05) as the Val:Lys ratio increased. In Exp. 2, ADG and ADFI increased (linear, P < 0.05) as Val:Lys increased. However, for ADG there was little improvement from feeding greater than 69% SID Val:Lys. There were no linear or quadratic effects (P > 0.05) for SID Val:Lys on G:F or PUN. Valine intake, Lys intake, and Val intake per kg of gain increased (linear, P < 0.05) as the Val:Lys ratio increased. There were no differences (P > 0.05) observed in Lys intake per kg of gain. Based on the results of this study, it appears that 66% SID Val:Lys ratio maximizes ADG in 38to 67 kg pigs, and only small increases in ADG were observed when feeding greater than 69% SID Val:Lys for 90 to 116 kg finishing pigs.

140 Response of 6 to 13 kg nursery pigs to increasing SID Arg:Lys

Abstract Newly weaned pigs (n = 480; PIC 337 × 1050; Genus, Hendersonville, TN) with an initial body weight (BW) of 6.20 ± 0.61 kg were used in a dose-response study to evaluate the effects of increasing standardized ileal digestible (SID) Arg:Lys in nursery pigs. At weaning, pigs were placed into 48 pens with five barrows and five gilts per pen and randomly assigned to one of six dietary treatments. The experimental diets were formulated with increasing levels of SID Arg by replacing corn starch, glycine, and L-alanine with L-arginine. Levels of SID Arg:Lys ranged from 45 to 145%. Diets were sub-limiting in SID Lys and exceeded all other essential amino acid requirements. Furthermore, diets were formulated to be isocaloric, isonitrogenous, and met or exceeded NRC (2012) vitamin and mineral recommendations. The experimental diets were fed in two feeding phases from d 0 to 10 and d 10 to 27, with adjustments made to account for the decreasing Lys requirement of the pigs. Pigs were subsequently fed a common diet for the remaining 14 d of the nursery period to determine carryover effects. Pigs and feeders were weighed at the beginning and end of each dietary phase for the calculation of average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (gain to feed ratio; G:F). The data were fit using linear regression with R version 4.3.1 (R Core Team, 2023). The model included linear and quadratic effects of SID Arg:Lys and initial BW. Pen was the experimental unit, and results were considered significant at P ≤ 0.05 and a tendency at 0.05 < P ≤ 0.10. There was a significant linear and quadratic effect of SID Arg:Lys on BW on d 27 (P ≤ 0.024), where BW was maximized at a SID Arg:Lys 97.09%. From d 0 to 27 there was a linear and quadratic tendency of SID Arg:Lys on ADFI (P = 0.069), where feed intake was maximized at a SID Arg:Lys of 97.00%. Furthermore, there tended to be a linear and quadratic effect of SID Arg:Lys on ADG from d0 to 27 (P ≤ 0.081), where ADG was maximized at a SID Arg:Lys of 95.65%. There was no evidence for an effect of SID Arg:Lys on G:F at any timepoint throughout the trial (P ≥ 0.298). In conclusion, SID Arg:Lys linearly and quadratically impacted ADFI and ADG in 6 to 13 kg nursery pigs, where ADG was maximized at a SID Arg:Lys of 95.65%, but ADFI was maximized at a SID Arg:Lys of 97.00%. Together, these data suggest that the SID Arg:Lys requirement of nursery pigs is greater than NRC (2012) recommendations, and excessive Arg supplementation may have negative consequences on growth performance.

26 Effects of increasing net energy or standardized ileal digestible lysine in soybean meal-based diets on early and late finishing pig performance

Abstract A total of 2,265 finishing pigs [337×1050, PIC; initial body weight (BW) = 50.2 kg) were used in two 28-d trials to determine the effect of increasing net energy (NE) or standardized ileal digestible Lys in soybean meal (SBM) based diets on early and late finishing pig performance. There were 27 pigs/pen and 21 pens/treatment. Soybean meal NE value used in diet formulation was either 78% (2,087 kcal/kg) or 100% (2,672 kcal/kg) of corn NE. Four treatment diets were assigned to pens in a completely randomized design and consisted of: 1) high level of SBM estimated at 100% NE of corn (High SBM); 2) low level of SBM estimated at 100% NE of corn with added feed-grade AA (Low SBM); 3) low level of SBM estimated at 78% NE of corn with added fat (Low SBM w/fat) to equal the NE in diets 1 and 2; and 4) low level of SBM estimated at 100% NE of corn with increased feed-grade AA and increased Lys:NE (Low SBM w/AA). Following the early finishing 28-d growth trial (initial BW = 50.2 kg), pigs were fed a common diet for 30-d and pens were randomly reallotted to 1 of the same 4 treatments for the late finishing trial (initial BW 114.1 kg). In early finishing, there were no differences (P > 0.10) in average daily gain (ADG), but pigs fed Low SBM w/AA had increased (P < 0.05) average daily feed intake (ADFI) compared with pigs fed High SBM (Table). The increased ADFI without increased ADG resulted in decreased (P < 0.05) gain to feed ratio (G:F) in pigs fed Low SBM w/AA compared with pigs fed Low SBM w/fat. Pigs fed Low SBM w/fat had improved (P < 0.05) caloric efficiency (CE) compared with pigs fed Low SBM w/AA. In late finishing, there was a tendency (P = 0.099) for a treatment effect on G:F where pigs fed High SBM had the greatest G:F, but there was not a significant difference (P > 0.05) between any two treatments when using a Tukey multiple comparison adjustment. There was no evidence (P > 0.10) for a difference between treatments on ADG, ADFI, or CE. Based on the performance of pigs fed the Low SBM w/AA diet, the decreased growth performance of low SBM diets is not due to a low Lys:Calorie ratio that results when NE is underestimated. Using caloric efficiency, an estimate of the NE of SBM was calculated by adjusting NE of SBM used in formulation until CE for the High SBM and Low SBM treatments were equal. These results showed SBM was estimated to contain 94% the NE of corn in the early finishing period and 125% the NE of corn in the late finishing period.

29 Effects of using different dietary standardized ileal digestible lysine plans on growth performance and carcass characteristics of PIC 337 or PIC 800 sired grow-finish pigs

Abstract The present study aimed to evaluate the impact of using different dietary standardized ileal digestible (SID) lysine (Lys) plans on growth performance of PIC 337 and PIC 800 sired grow-finish pigs. A total of 2,016 gilts and barrows were placed in 2 separate rooms with 48 single sex pens each (21 pigs/pen; 0.69 m2/pig). Pens were blocked by body weight (BW) and randomly allotted in a 2 × 2 × 2 factorial arrangement with genetic line (PIC 337 or 800), sex (barrows or gilts), and nutrition plan (current SID Lys curve recommendation for PIC 800 as % of PIC 337 SID Lys curve or alternative SID Lys curve) as factors. Pigs (27.4 ± 1.41 kg BW) were followed during the grower-finisher phase until slaughter. Pigs were fed either the current recommendation or an alternative SID Lys curve for PIC 800, in a 5 phase feeding program: phase 1 (23-40 kg; 97 vs 100%, respectively); phase 2 (40-60 kg; 97 vs 95%, respectively); phase 3 (60-80 kg; 97 vs 95%, respectively); phase 4 (80-105 kg; 97 vs 95%, respectively); and phase 5 (105-135 kg; 97 vs 90%, respectively). Pigs were fed isoenergetic diets. Performance and carcass traits, and removals and mortality were recorded. Data were analyzed using mixed models in R, and considering pen as the experimental unit for performance traits and individual carcasses for carcass traits. There was no evidence of interaction between genetic line and nutrition plan factors. Overall, PIC 337 vs 800 pigs did not differ on average daily gain (ADG; P > 0.05), but PIC 337 pigs consumed 150 g/d less and were 0.1 more feed efficient than PIC 800 pigs (P < 0.05; Table 1). Moreover, PIC 337 pigs had 1.9 kg less of hot carcass weight, but 2.1 mm more of loin depth compared with PIC 800 pigs (P < 0.05; Table 1). Regarding nutrition plan, no significant differences were observed for overall performance and carcass traits between pigs fed the current or alternative SID Lys curve (P > 0.05; Table 1). Additionally, no significant differences were observed for overall removals and mortality by genetic line or nutrition plan (P > 0.05; Table 1). In summary, different genetic sire line (PIC 337 and PIC 800) differed on performance and carcass traits. Further research is needed to continue studying the genetic evolution and nutrition plan for each genetic sire line in the grower-finisher period to understand their nutrient requirements.

30 Effects of using different dietary standardized ileal digestible lysine plans on growth performance and carcass characteristics of grow-finish pigs from high or low breeding value boars

Abstract The present study aimed to evaluate the impact of using different dietary standardized ileal digestible (SID) lysine (Lys) plans on growth performance and carcass characteristics of grow-finish pigs coming from high or low breeding value boars. A total of 2,080 pigs (PIC 800 × PIC Camborough) were housed in 20 mixed sex pens (26 pigs/pen), blocked by body weight (BW), and randomly allotted in a 2 × 2 factorial arrangement with boar breeding value (high or low) and nutrition Lys plan (current SID Lys curve recommendation for PIC 800 as % of PIC 337 SID Lys curve or alternative SID Lys curve). Pigs were weaned at 21 d of age (6.1 ± 0.05 kg BW) and followed during the wean-to-finish period until reach the market slaughter weight. Pigs were fed either the current recommendation or an alternative SID Lys curve for PIC 800, in a 6 phase feeding program: phase 1 (6-11 kg; 100 vs 100%, respectively); phase 2 (11-23 kg; 97 vs 100%, respectively); phase 3 (23-45 kg; 97 vs 100%, respectively); phase 4 (45-73 kg; 97 vs 95%, respectively); phase 5 (73-102 kg; 97 vs 95%, respectively); and phase 6 (102-132 kg; 97 vs 90%, respectively). Pigs were fed isoenergetic diets. Performance and carcass traits, and removals and mortality were recorded. Data were analyzed using mixed models in R, and considering pen as the experimental unit for performance traits and individual carcasses for carcass traits. There was no evidence of interaction between boar breeding value and nutrition plan factors. Overall, high breeding value pigs had greater average daily gain (ADG; 0.84 ± 0.005 g/d) compared with low breeding value pigs (0.82 ± 0.005 kg/d; P < 0.01), which was driven by increased average daily feed intake (ADFI; 1.92 ± 0.011 and 1.89 ± 0.011 kg/d, respectively; P < 0.05; Table 1). Moreover, high breeding value pigs had greater hot carcass weight (HCW; 97.8 ± 1.09 kg), carcass yield (74.1 ± 0.23%), backfat thickness (16.3 ± 0.29 mm) and lower lean meat % (57.0 ± 0.21%) compared with low breeding value pigs (96.0 ± 1.09 kg; 73.7 ± 0.23 %; 15.4 ± 0.28; 57.5 ± 0.21%, respectively; P < 0.05; Table 1). Regarding nutrition plan, no significant differences were observed for overall performance traits between pigs fed the current or alternative SID Lys curve (P > 0.05; Table 1). Nevertheless, pigs fed the alternative SID Lys curve had heavier HCW (97.3 ± 1.09 kg) compared with pigs fed the current SID Lys curve (96.6±1.09 kg; P < 0.05; Table 1). No significant differences were observed for overall removals and mortality by breeding value or nutrition Lys plan (P > 0.05). In summary, grow finish pigs from high breeding value boars have an improved productive performance. PIC 800 pigs may achieve the same productive performance with lower lysine levels at the end of the grow-finish period.

27 Standardized ileal digestible lysine to metabolizable energy ratio equations for 12 to 127 kg boars, gilts, immunocastrated gilts and boars

Abstract We aimed to determine the standardized ileal digestible (SID) lysine (Lys) to metabolizable energy (ME) ratio equations for 12 to 127 kg boars, gilts, immunocastred gilts (IC gilts), and barrows (IC barrows). An average of 3,545 split-gender pigs (PIC 337×Camborough, initially 11.98 ± 1.26 kg) were used in a 21-d trial followed by a 21-d wash-out period in 2 replicates, totaling six feeding periods. In feeding phase 6, both genders were immunized against gonadotropin-releasing hormone (administrated with Vivax, Zoetis, São Paulo, SP, Brazil). Pens of pigs were weighed, blocked by body weight, and randomly allotted to 1 of 5 treatments consisting of 80, 90, 100, 110, and 120% of PIC SID Lys:Mcal of ME recommendations for mixed gender between boars, barrows, and gilts for each phase. The treatment diets were corn-soybean-meal-based and contained 3,300 Kcal of ME/kg. There were six split-gender pens•treatment-1•replicate-1 •phase-1 and 30 pigs/pen. Data were analyzed using generalized linear and nonlinear mixed models with a pen as the experimental unit. Competing models included linear, quadratic polynomial (QP), broken-line linear (BLL), and broken-line quadratic (BLQ) for average daily gain (ADG) and gain to feed ratio (G:F). There was no significant gender by quadratic coefficient interactions in all phases of this study (P > 0.05), then the mixed gender equation was determined, and the intact boars and gilts equation was estimated by the PIC overall difference in efficiency between genders. In the immunocastrated phase, after second dose, the mixed gender optimum level was determined and the equations for IC gilts and barrows was estimated by the differences in efficiency observed in the phase 6 of the two replicates. The SID Lys to calorie ratio recommended is based on the average for ADG and G:F (Table 1). Approximately 98.4% and 99.2% of maximum ADG and G:F were achieved at these levels, respectively, and these equations were similar compared with previous PIC biological requirements (Orlando et al., 2021).

Effect of dietary nitrogen content and ammonium phosphate inclusion on lysine requirement for nitrogen retention in growing pigs

Inclusion of a source of non-protein nitrogen (NPN) may improve essential amino acid (EAA) and nitrogen (N) utilization in N-limiting diets. Growing barrows (20.4 ± 0.5 kg) were randomly assigned to 1 of 10 dietary treatments ( n = 9 pigs/treatment) in nine blocks. Diets contained no ammonium phosphate (NAP) or 1.7% ammonium phosphate (AP) to have an EAA-N:total N ratio of 0.36 and 0.33, respectively, with graded levels of dietary lysine (Lys; 0.8%, 0.9%, 1.0%, 1.1%, and 1.2% standardized ileal digestible (SID)). Following a 7-day dietary adaptation, a 4-day N-balance collection period was conducted. Blood samples were obtained on day 2 of the collection period. Nitrogen retention (NR) increased and urinary N output decreased with inclusion of NPN and increasing Lys ( P < 0.01). Plasma urea N decreased with increasing Lys ( P < 0.05). Total plasma EAA content was reduced with NPN supplementation ( P < 0.05), while content of Arg, Asp, Gln, and Glu was increased ( P < 0.01). The linear breakpoint model indicated that NR was maximized at 1.00% SID Lys in NAP-fed pigs and at 1.09% SID Lys in AP-fed pigs. These results indicate that diets deficient in dietary N reduce NR and Lys requirement, which were in turn increased with NPN supplementation.

Growth performance, serum parameters, inflammatory responses, intestinal morphology and microbiota of weaned piglets fed 18% crude protein diets with different ratios of standardized ileal digestible isoleucine to lysine

The present study was to explore the Ile requirement of piglets fed 18% crude protein (CP) diets. Two hundred and fifty 28-day-old Duroc × Landrace × Yorkshire piglets (8.37 ± 1.92 kg) were randomly divided into 5 dietary treatments (10 piglets per replicate, 5 barrows and 5 gilts per replicate) with 45%, 50%, 55%, 60%, 65% standardized ileal digestible (SID) Ile-to-Lys ratios, and the SID Lys was formulated to 1.19%. The experimental design consisted of two phases (d 1 to 14 and d 15 to 28). Results showed that average daily gain (ADG) had a tendency to quadratically increase as the SID Ile-to-Lys ratio increased (P = 0.09), and the optimum SID Ile-to-Lys ratios required to maximize ADG were 48.33% and 54.63% for broken-line linear model and quadratic polynomial model, respectively. Different SID Ile-to-Lys ratios had no significant effects on average daily feed intake and gain-to-feed ratio. Dry matter (P < 0.01), CP (P = 0.01), ether extract (P = 0.04), gross energy (P < 0.01) and organic matter (P < 0.01) digestibility increased quadratically. Serum total cholesterol levels decreased linearly (P = 0.01) and quadratically (P < 0.01); aspartate aminotransferase (P < 0.01), interleukin-1β (P = 0.01), and tumor necrosis factor-α (P < 0.01) levels decreased quadratically; immunoglobulin G (P = 0.03) and immunoglobulin M (P = 0.01) concentrations increased quadratically. Serum Ser levels decreased linearly (P < 0.01) and quadratically (P = 0.01); Glu (P = 0.02), Arg (P = 0.05), and Thr (P = 0.03) levels decreased quadratically; Gly (P < 0.01) and Leu (P = 0.01) levels decreased linearly; Ile (P < 0.01) concentration increased linearly. Duodenal villus height (P < 0.01) and villus height to crypt depth ratio (P < 0.01) increased quadratically. The deficiency or excess of Ile decreased short chain fatty acid-producing bacteria abundance and increased pathogenic bacteria abundance. Overall, taking ADG as the effect index, the optimum SID Ile-to-Lys ratios of piglets offered 18% CP diets were 48.33% and 54.63% based on two different statistical models, respectively, and the deficiency or excess of lle negatively affected piglet growth rates and health status.

208 Effect of SID LYS Level with Constant Non-Essential Amino Acids

Abstract Many investigations on the effect of low protein diets reduce crude protein (CP) and have a constant standardized ileal digestible (SID) LYS resulting in reductions in ADG, ADFI, and gain:feed is some cases. This experiment was conducted to determine the impact of maintaining constant non-essential amino acids and changing SID LYS and other essential amino acids. For the experiment, 288 pigs (~22 d of age, 6.61 ± 0.95 kg, 8 replicates/treatment, 6 pigs/pen) were stratified by body (BW) and randomly allotted to one of 6 treatments in a randomized complete block design. Non-essential amino acids were fixed in all diets and synthetic amino acids were added to increase SID LYS from 1.15% to 1.4% while maintaining constant ratios of MET+CYS, THR, TRP, VAL, and ILE to LYS. Diets were corn, wheat, barley, and soy based with 1.1% corn starch in the least SID LYS diet. Synthetic amino acids were added to the diet at the expense of corn starch to maintain non-essential amino acid levels. The CP ranged from 17.8% when SID LYS was 1.15% and 18.6% when SID LYS was 1.4%. Experimental diets were fed for 21 d. Body weight, feed disappearance, visual fecal scores, and visual piglet scores were measured. Visual fecal scores (1 = normal to 4 = watery) and visual pig appearance scores (1 = pale and hairy to 4 = normal color and well-rounded muscle) were assessed on ordered likert scales to determine the probabilities of observing a more normal stool quality and a worse visual appearance, respectively. Performance data were analyzed as a general linear model. Stool quality and visual appearance were analyzed as a generalized linear mixed model. Contrasts were used to test linear and quadratic effects of dietary SID LYS. Results of the experiment are presented in Table 1. Increasing SID LYS with constant non-essential amino acids did not affect ADG or BW. The ADFI was linearly decreased (P &amp;lt; 0.1) and gain:feed was linearly increased (P &amp;lt; 0.0001) with increasing SID LYS (Table 1). Stool quality was not affected. Visual appearance of the pigs was quadratically affected (P &amp;lt; 0.05) by changing SID LYS. Pigs that had consumed diets with the lowest or highest SID LYS had the best visual appearance (lowest probability). The results of the current experiment differ suggest SID LYS may regulate feed intake and nutrient efficiency, but BW gain is not affected when non-essential amino acids are held constant. This differs from cases where CP is reduced, which results are decreased growth in many cases.

214 Effects of Dietary Standardized Ileal Digestible (SID) Lysine (Lys) Levels and Dietary SID Tryptophan to Lys Ratios on Growth Performance of Late-Nursery Maternal Barrows

Abstract The objective was to determine the effects of dietary standardized ileal digestible (SID) lysine (Lys) levels and SID tryptophan (Trp) to Lys ratios on the growth performance of late-nursery maternal barrows. A total of 2,293 barrows (PIC Camborough, initially 11.9 ± 0.35 kg) were used in a 28-day trial with 96 mixed-sex pens in two rooms (48 pens/room), 16 pens/treatment, and 23 to 25 pigs/pen. Pens were blocked by body weight (BW) and randomly allotted to 1 of 6 treatments in a 2×3 factorial arrangement. Treatment factors were: 1) Dietary SID Lys levels: meet PIC SID Lys recommendation at 1.234% (PIC LYS) or below PIC SID Lys recommendation at 0.988% (BELOW LYS); 2) Dietary SID Trp to Lys ratios: 21.0, 18.5, and 16.0. Data were analyzed using a linear mixed model in R Studio (Version 3.5.2, R Core Team; Vienna, Austria). Dietary SID Lys levels, dietary SID Trp to Lys ratios, and their interaction were included as fixed effects, and room and weight block were included as random effects in the model. Pigs fed with PIC LYS diets showed significantly improved average daily gain (ADG; 672 vs. 594 g; P &amp;lt; 0.001), average daily feed intake (ADFI; 1227 vs. 1179 g; P &amp;lt; 0.001), gain-to-feed ratio (G:F; 550 vs. 508 g/kg; P = 0.002), and greater amount of SID Lys intake (22.5 vs. 19.5; P &amp;lt; 0.05) or Trp intake (4.2 vs. 3.6; P &amp;lt; 0.05) per kg of BW gain comparing to BELOW LYS diets. Significant interactive effects were observed between dietary SID Lys levels and dietary SID Trp and Lys ratios on final BW, ADG, ADFI, and G:F (P &amp;lt; 0.05; Table 1). For final BW and ADG, when feeding PIC LYS diets, decreasing dietary SID Trp to Lys ratios increased final BW and ADG (quadratic, P &amp;lt; 0.05); but when feeding BELOW LYS diets the decreasing ratios reduced final BW and ADG (quadratic, P &amp;lt; 0.05). For ADFI, when feeding PIC LYS diets, there was no evidence that decreasing dietary SID Trp to Lys ratios impacted ADFI (P &amp;gt; 0.05); but when feeding BELOW LYS diets the decreasing ratios reduced ADFI (quadratic, P &amp;lt; 0.05). When feeding PIC LYS diets, the decreasing dietary SID Trp to Lys ratios decreased and then increased G:F (quadratic, P &amp;lt; 0.05); but when feeding BELOW LYS diets, the decreasing ratios increased and then decreased G:F (quadratic, P &amp;lt; 0.05). In conclusion, late-nursery maternal barrows fed the PIC LYS diet had improved growth performance compared with those fed BELOW LYS diet; and decreasing dietary SID Trp to Lys ratios from 21.0 to 16.0 had deleterious impacts on growth performance when dietary SID Lys level was below PIC recommendation, but not when dietary SID Lys level met PIC recommendation.

212 Effect of Low Crude Protein Diets in Young Pigs When Using Crystalline Isoleucine and Leucine

Abstract An experiment was conducted to evaluate the response to low crude protein (CP) while maintaining equal standardized ileal digestible (SID) LYS and equal SID amino acid-to-LYS ratios (including MET+CYS, THR, TRP, VAL, ILE, and LEU) to test whether the addition of LEU and ILE allowed CP to decline below 19.5% without impacting performance when SID LYS was 1.35%. For the experiment, pigs (n = 288; ~22 days of age, 6.29 ± 0.71 kg BW, 8 reps/treatmentt, 6 pigs/pen) were stratified by BW and randomly allotted to one of 6 treatments in a randomized complete block design. Treatments had a fixed SID LYS of 1.35% and CP ranging from 21 to 17.25% in 0.75% increments. Experimental diets were fed for 21 days, and BW and feed disappearance were recorded. Visual fecal scores (1 = normal to 4 = watery) and visual pig appearance scores (1 = pale and hairy to 4 = normal color and well-rounded muscle) were assessed on ordered likert scales to determine the probabilities of observing a more normal stool quality and a worse visual appearance, respectively. Performance data were analyzed as a general linear model. Stool quality and visual appearance were analyzed as a generalized linear mixed model. Contrasts were used to test linear and quadratic effects of dietary CP. Results of the experiment are presented in Table 1. With constant SID Lys of 1.35%, reducing CP from 21.00 to 17.25% resulted in an increase then a decrease (linear, P &amp;lt; 0.005; quadratic, P &amp;lt; 0.005) in BW, ADG, ADFI, and gain:feed. Average daily gain and ADFI began decreasing when CP decreased below 20.25%, whereas body weight and gain:feed began decreasing once CP was below 19.50%. There was a difference detected amongst treatments in stool quality, but this was not due to changes in crude protein levels of the diets. This suggests that protein fermentation was not directly impacting stool quality in these pigs. Decreasing dietary CP also linearly (P &amp;lt; 0.05) and quadratically (P &amp;lt; 0.05) affected the visual appearance of the pigs in a similar manner to performance. At the least levels of crude protein, pigs had a greater probability of having more coarse hair and paler skin suggesting that a nutritional stress response may be occurring. These results indicate that the addition of ILE and LEU to the formula do not allow CP to decrease below 19.5% without affecting performance when SID LYS is 1.35 in young pigs.

130 Effects of Increasing Dietary Standardized Ileal Digestible Lysine Levels on Growth Performance of 102- to 127-kg Immunocastred Gilts and Boars

Abstract Our objective was to determine the effects of increasing dietary standardized ileal digestible (SID) lysine (Lys) on growth performance of immunocastrated gilts and boars. A total of 3,519 split gender pigs [PIC 337×Camborough, initial body weight (BW) = 101.7 ± 3.89 kg] were used in a 21-d trial in 2 replicates. Following the immunization against gonadotropin-releasing hormone (administrated with Vivax, Zoetis, São Paulo, SP, Brazil) in both genders, pens of pigs were weighed, blocked by BW, and randomly allotted to 1 of 5 treatments. Treatments consisted of 1.69, 1.90, 2.11, 2.32, and 2.53 g of SID Lys:Mcal of ME, which corresponded to 80, 90, 100, 110, and 120% of PIC SID Lys recommendations for mixed gender between barrow and gilts. This resulted in 0.56, 0.63, 0.70, 0.77, and 0.84% SID Lys given that the treatment diets were corn-soybean-meal-based and contained 3,300 Kcal of ME/kg. There were 6 split gender pens∙treatment-1∙replicate-1 and 29 pigs/pen. Data were analyzed using generalized linear and nonlinear mixed models with a pen as the experimental unit. Competing models included linear, quadratic polynomial (QP), broken-line linear (BLL), and broken-line quadratic (BLQ). There was no evidence of linear or quadratic SID Lys concentration by gender interaction (Table). Increasing SID Lys concentration improved average daily gain (ADG; quadratic, P &amp;lt; 0.01) and gain-to-feed ratio (G:F; quadratic, P &amp;lt; 0.01). The QP, BLL, and BLQ had a similar fit for the ADG and G:F. In the QP model, 95% and 100% of the ADG were achieved at 0.64 and 0.76% of SID Lys, respectively, and at 0.61 and 0.75% for G:F. The BLL and BLQ models estimated the breakpoint at 0.70% (95% CI: 0.65-0.74%) and 0.68% SID Lys (95% CI: 0.50-0.85%), for ADG, respectively. For G:F, the BLL, and BLQ models estimated the breakpoint at dietary SID Lys of 0.69% (95% CI: 0.52-0.86%) and 0.68% (95% CI: 0.58-0.78%), respectively. There was no evidence that increasing dietary SID Lys levels impacted the average daily feed intake or the removal and mortality rate. In the current trial the estimated optimum SID Lys:Mcal of ME ratio for 102- to 127-kg immunocastrated gilts and boars ranged from 2.06-2.30 (0.68-0.76% SID Lys based on a 3,300 kcal of ME/kg diet), depending on the statistical model.

134 Meta-Analysis to Determine the Standardized Ileal Digestible Lysine Requirements of Growing-Finishing Pigs from 11- to 150-kg Utilizing the Ingredients Database of Inra

Abstract A meta-analysis was conducted to determine the standardized ileal digestible (SID) lysine (Lys) recommendations for 11–150 kg PIC pigs housed under commercial conditions utilizing the INRA feed ingredients database. Data from 29 trials dating from 2013 to 2020 utilizing 48,338 pigs were recorded in a database. Number of pens/treatment and pigs/pen ranged from 9 to 16 and 12 to 25, respectively. Sire lines were PIC 337 in 25 trials, PIC 327 in 3 trials, and PIC TR4 and 327 in 1 trial. Dam lines were PIC Camborough in 18 trials and PIC Camborough 29 in 9 trials. The SID Lys levels reported in each trial were used, and the SID Lys to calorie ratio curves were built for both metabolizable energy (ME) and net energy (NE) systems using the feed ingredient composition in INRA for energy levels. The response variables, average daily gain (ADG) and feed efficiency (G:F), were analyzed within 7 phases using generalized linear and non-linear mixed models with heterogeneous variance (Gonçalves et al., 2016). Phases consisted of the following body weight ranges: 11-23, 23-41, 41-59, 59-77, 77-104, 104-127, and 127-150 kg . Each treatment mean within a trial (n = 288) was considered the experimental unit and each trial was used as a random effect. There was no evidence for an interaction between sire lines or dam lines and treatment (P &amp;gt; 0.10). The SID Lys to calorie recommendations are based on the average of the requirement estimates for ADG and G:F. At these levels, approximately 100% of maximum ADG and 99.7% of maximum G:F are achieved. After determining the requirement estimates within each of the 7 weight breaks, a quadratic equation of Lys to calorie ratio was fit for each energy system. The equations are described as: g of SID Lys:Mcal of ME = 0.0001381709 × (weight, kg)2 - 0.0366272129 × (weight, kg) + 4.6073086522; and g of SID Lys:Mcal of NE = 0.0000400092 × (weight, kg)2 - 0.0235648387 × (weight, kg) + 6.2762350341. These data provide the estimated SID Lys requirements for maximal growth performance for PIC pigs from 11- to 150-kg based on the ingredients database of INRA.