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An experiment was conducted to determine the effects of soybean meal (SBM) inclusion rate on growth performance of growing pigs. A total of 1,722 pigs (initial BW = 41.1 kg), placed in pens with 20 or 21 pigs each, were used in a 49-d trial. There were 2 treatments consisting of different SBM inclusion rates. Experimental diets were fed in 3 phases. Treatment 1 (low SBM) contained 18, 14, and 12% SBM and Treatment 2 (high SBM) contained 26, 22, and 19% SBM in phases 1, 2, and 3, respectively. The different SBM levels were obtained by adjusting the inclusion rate of synthetic amino acids. Both treatments were formulated to the same SID Lys (1.00, 0.92, and 0.85% in phases 1, 2, and 3, respectively) and net energy levels (2,565, 2,575, and 2,581 kcal/kg in phases 1, 2, and 3, respectively). The net energy of SBM used in diet formulation was equivalent to 90% of corn net energy. There were 42 replicates per treatment. Pigs were weighed approximately every 2 weeks to calculate ADG, ADFI, G:F, and caloric efficiency. Data was analyzed with SAS MIXED procedure. Overall (d 0 to 49), there was no evidence for differences (P > 0.10) on ADG, ADFI, or final BW. Pigs fed the high SBM diets had improved (P < 0.01) G:F and caloric efficiency. The removal and mortality rate was 1.05% (9 pigs) on the low SBM treatment and 0.46% (4 pigs) on the high SBM treatment. In conclusion, increasing levels of SBM resulted in improved G:F and caloric efficiency of growing pigs.

An experiment was conducted to determine the optimal standardize ileal digestible (SID) Lys level for growth performance of nursery pigs. A total of 980 pigs (PIC 337 × Camborough; initial BW = 5.4 kg), placed in pens with 28 pigs each, were used in a 42-d trial. There were 5 treatments consisting of 1.15, 1.25, 1.35, 1.45, or 1.55% SID Lys. Experimental diets were fed from d 0 to 21 followed by a common corn-soybean meal-based diet (1.30% SID Lys) from d 21 to 42. Pigs were weighed weekly to calculate ADG, ADFI, and G:F. Data was analyzed with SAS MIXED procedure. From d 0 to 21, increasing the SID Lys level resulted in a linear (P < 0.01) ADG, G:F, and BW improvement. Because of the linear nature of the response, the breakpoint could not be determined. From d 21 to 42, when pigs were fed a common diet, linear (P < 0.05) ADG and G:F responses were observed; pigs previously fed the lower SID Lys levels had improved performance. This compensatory response resulted in no evidence for differences (P > 0.10) in overall (d 0 to 42) ADG and final BW, although there was a linear (P = 0.004) G:F improvement. In conclusion, increasing SID Lys level linearly improved performance; however, pigs fed low SID Lys levels presented compensatory growth and obtained similar performance in the overall nursery period.

An experiment was conducted to compare the effects of increasing dietary net energy (NE) in finishing pig diets while either maintaining a standardized ileal digestible lysine:NE ratio (SID Lys:NE) or maintaining SID Lys as a constant percentage of the diet across increasing energy densities. A total of 150 pigs (Line 600 × 241; DNA, Columbus, NE; initially 35.7 kg) were used in a 91-d study. Pigs were blocked by sex and weight and randomly assigned to 1 of 5 treatments with 2 pigs per pen and 15 pens per treatment. Treatments included a low-energy control diet that was corn-soybean meal-based with added soybean hulls, and a 2 × 2 factorial arrangement of treatments with main effects of increasing dietary NE (medium or high by adding choice white grease) and formulation method (with a SID Lys:NE ratio or maintaining the same percentage SID Lys). Linear and quadratic contrasts were made using the control diet and the medium- and high-energy diets within each formulation method. Pigs and feeders were weighed approximately every 30 d to calculate average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F). At the end of the experiment, pigs were sent to a commercial processing facility for carcass data collection. From days 0 to 34 and 34 to 61, ADG and SID Lys intake increased as NE increased (linear, P < 0.05) in pigs fed diets with a Lys:NE ratio, but not for those fed the same percentage Lys. As NE increased, NE intake and G:F increased (P < 0.01) in pigs fed diets with either formulation method. From days 61 to 91, increasing NE had no effect (P > 0.10) on ADG. There was no change in G:F in pigs fed diets with the same percentage Lys (P > 0.10), but G:F decreased then increased (quadratic, P < 0.01) in response to increasing NE in pigs fed diets with a SID Lys:NE ratio. Overall, increasing dietary NE increased (linear, P < 0.001) daily NE intake and G:F (linear, P < 0.018) with either formulation method. However, SID Lys intake, ADG, and hot carcass weight only increased (linear, P < 0.01) when a SID Lys:NE ratio was maintained. Increasing NE without maintaining a constant SID Lys:NE ratio increased backfat depth (quadratic, P = 0.01), whereas it did not in pigs fed diets with a SID Lys:NE ratio. In conclusion, increasing dietary energy density increased NE intake and G:F regardless of formulation method. However, a SID Lys:NE ratio must be maintained to achieve increased ADG and minimize fat deposition.

The branched-chain amino acids (BCAA) Leu, Ile, and Val share the first steps of their catabolism due to similarities in their structure. The BCAA are reversibly transaminated in skeletal muscle through the activity of branched-chain aminotransferase and then transported to the liver. They undergo an irreversible decarboxylation catalyzed by the branched-chain α-keto acid dehydrogenase complex. Both enzymes are common to Leu, Ile, and Val and increased enzymatic activity stimulated by an excess of one of them will increase the catabolism of all BCAA, which can result in antagonisms. Leucine and its keto acid are the most potent stimulators of BCAA catabolic enzymes. Moreover, BCAA and large neutral amino acids (LNAA) share common brain transporters. Research has shown that high concentrations of BCAA, especially Leu, can decrease the absorption of LNAA, such as Trp, which is a precursor of serotonin and can have a significant impact in feed intake regulation. Finally, high Leu concentrations have the ability to overstimulate the mTOR signaling pathway, resulting in an inhibitory effect on feed intake. Most of the research conducted to evaluate the impact of BCAA on growth performance of pigs seems to agree that high levels of Leu decrease weight gain, mostly due to a reduction in feed intake. However, some studies, mostly with finishing pigs, observed no evidence for an impact on growth performance even with extremely high levels of Leu. It could be hypothesized that these inconsistencies are driven by the entire dietary amino acid profile as opposed to only considering the level of Leu. Grow-finish diets typically contain high levels of Leu, but the other BCAA are also well above the requirement and could potentially mitigate the negative impact of Leu on BCAA catabolism. Indeed, some studies suggest that when diets contain high levels of Leu, more Ile and Val are needed to optimize growth performance. However, the precise relationship between BCAA and their balance in swine diets is not fully understood. More research is needed to understand and quantify the relationship between LNAA and BCAA.

A total of 2,430 pigs (PIC 337 × 1050; Hendersonville, TN; initially 30.1 kg) were used in a 113-d growth trial to determine the effects of increasing dietary Zn on growth performance and carcass characteristics of finishing pigs raised under commercial conditions. Pens of pigs were assigned to be fed one of five dietary treatments in a randomized complete block design. Treatments consisted of 50, 87.5, 125, 162.5, or 200 mg/kg added Zn from Zn hydroxychloride (IntelliBond Z, Micronutrients, Indianapolis, IN). Two identical barns were used for a total of 18 pens per treatment with 27 pigs per pen. Experimental diets were fed in five phases and contained a vitamin-trace mineral premix without added Zn. Pens of pigs were weighed approximately every 2 wk to calculate average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F). At the end of the experimental period, pigs were tattooed with a pen identification number and transported to a packing plant to measure hot carcass weight (HCW), backfat, loin depth, and calculated lean percentage. Data were analyzed block nested within barn as a random effect and pen as the experimental unit. From days 0 to 42, pigs fed diets with increasing added Zn had lower (linear, P = 0.043) ADFI and a tendency (P = 0.092) for lower ADG. From days 42 to 113, increasing added Zn resulted in a quadratic response (P = 0.042) for ADFI and a tendency (linear, P = 0.056) for improved G:F. Overall (days 0 to 113), there were tendencies for quadratic responses for ADFI (P = 0.073) and G:F (P = 0.059), with the greatest G:F observed when 125 mg/kg of Zn was fed. Increasing added Zn resulted in a linear increase (P < 0.001) in daily Zn intake. There were no differences (P > 0.10) in overall ADG, final body weight, HCW, backfat, loin depth, lean percentage, mortality, and removal rate. In conclusion, there were no improvements in ADG when feeding beyond 50 mg/kg added Zn; however, providing 125 mg/kg added Zn resulted in the greatest G:F.

An experiment was conducted to determine the effects of the initial nursery diet budget on growth performance. A total of 3,264 pigs (initial BW = 5.5 kg), placed in pens with 51 pigs each, were used in a 45-d trial. There were 4 treatments consisting of different feed budgets of the initial nursery diet: 4.1 kg, 5.4 kg, 6.8 kg, or 8.2 kg. The experimental diet was corn, soybean meal, and whey permeate-based and contained 1.38% SID Lys. After the allocated budget was consumed, pigs were provided a common corn and soybean meal-based diet. There were 16 replicates per treatment. Pigs were weighed weekly to calculate ADG, ADFI, and G:F. Data were analyzed with SAS MIXED procedure. In the first 14 d of the trial there was no evidence for differences (P > 0.10) in growth performance as all pigs were receiving their allocated budget of the initial diet. From d 14 to 21 as well as d 0 to 21, pigs that received a budget of 6.8 or 8.2 kg had improved ADG (quadratic, P < 0.05) and G:F (linear, P < 0.05) compared to those fed budgets of 4.1 or 5.4 kg. From d 21 to 45, when all pigs received a common diet, there was no evidence for differences (P > 0.10) in ADG. However, there was a linear response (P < 0.05) in G:F, with pigs previously fed the lowest feed budget presenting improved G:F. Overall (d 0 to 45), there was an improvement (linear, P < 0.05) in ADG and ADFI as feed budgets increased, with the best performance observed when pigs were fed 6.8 or 8.2 kg of the initial nursery diet. In conclusion, providing a 6.8 or 8.2 kg budget of the initial nursery diet resulted in improved overall nursery performance.

An experiment was conducted to determine the effects of added Zn level on growth performance and hemoglobin of nursery pigs. A total of 673 pigs (initial BW = 6.0 kg) were used in a 45-d trial. There were 3 treatments based on added Zn level: 100, 2,000, or 3,000 mg/kg from Zn oxide. Experimental diets were fed for 21 d. After that, pigs were fed a common corn and soybean meal-based diet with 100 mg/kg added Zn for 24 d. There were 8 replicates per treatment. Pigs were weighed approximately every 10 d to evaluate growth performance, and blood samples were collected for hemoglobin analysis. Data was analyzed with SAS MIXED procedure. From d 0 to 10, there was a linear improvement (P < 0.05) in ADG, ADFI, and G:F with increasing Zn level. From d 10 to 21, increasing Zn level resulted in higher ADFI (linear, P = 0.009). However, there was no difference (P > 0.10) in ADG and G:F. From d 0 to 21, pigs fed increasing added Zn had improved (linear, P < 0.05) ADG and ADFI. From d 21 to 45, pigs previously fed high levels of added Zn had higher ADFI (linear, P = 0.023), but there was no evidence for differences (P > 0.10) for ADG and G:F. Overall (d 0 to 45), pigs fed increasing added Zn levels had improved (linear, P < 0.05) ADG, ADFI, and final BW. A quadratic response (P < 0.05) was observed for hemoglobin on d 10 and 45, with no differences (P > 0.10) observed on d 21. In summary, pigs fed high levels of added Zn presented improved growth performance. Although the response was linear in nature, the differences between pigs fed 2,000 or 3,000 mg/kg Zn were minimal for the response variables evaluated.

Based on results of a recent meta-analysis, we hypothesized that increased dietary Val, Ile, or Trp could correct possible amino acid interactions because of excess Leu in diets containing high levels of corn protein, namely dried distiller’s grains with solubles (DDGS). A total of 1,200 pigs (PIC TR4 × (Fast LW × PIC L02); initially 33.6 ± 0.6 kg) were used in a 103-d study. The 6 dietary treatments were corn–soybean meal (SBM)-DDGS-based as follows: (1) high SBM and low level of l-Lys HCl (HSBM), (2) high l-Lys HCl and moderate Ile, Val, Trp (AA above NRC 2012 estimates; NC), (3) moderate l-Lys HCl and high Ile, Val, and Trp (PC), and PC with either increased (4) L-Val (PC+Val), (5) L-Ile (PC+Ile), or (6) L-Trp (PC+Trp). Pigs fed the NC diet were predicted to have the poorest average daily gain (ADG), the PC diet to be intermediate, and pigs fed the HSBM, PC+Val, PC+Ile, and PC+Trp have the same and highest predicted ADG. In the grower period (34 to 90 kg), ADG was greater (Ρ < 0.05) for the pigs fed HSBM and PC+Val diets than the NC with pigs fed other diets intermediate. Pigs fed HSBM were more (Ρ < 0.05) efficient (G:F) than the NC and PC with pigs fed other diets intermediate. In the finisher period (90 to 136 kg), ADG was greater (Ρ < 0.05) for pigs fed PC+Ile than that of the NC with pigs fed other diets intermediate. Pigs fed PC+Val had greater (Ρ < 0.05) average daily feed intake (ADFI) than the NC with pigs fed other diets intermediate. However, PC+Ile pigs were more (Ρ < 0.05) efficient than PC+Val with pigs fed other diets intermediate. Overall, ADG was greater (Ρ < 0.05) for pigs fed HSBM, PC+Val, and PC+Ile diets than the NC with pigs fed other diets intermediate. Pigs fed the PC+Val diet had greater (Ρ < 0.05) ADFI than the NC with pigs fed other diets intermediate. No differences were detected between treatments for overall G:F or other carcass characteristics. In conclusion, increasing Val or Ile in high l-Lys-HCl-DDGS-based diets improved growth performance compared with pigs fed diets containing high levels of l-Lys HCl without added Val and Ile. These results present evidence that the recently developed meta-analysis can predict the relative differences in overall ADG for pigs fed the NC, PC, PC+Val, and PC+Ile diets; however, the predicted G:F was less accurate. The data demonstrate that the negative effects of high Leu concentrations in corn-DDGS-based diets can be reversed by increasing the ratios of Val and Ile relative to Lys.

Production systems commonly have multiple fill events in the nursery, which can lead to inaccurate feeding of dietary budgets. A simpler feeding program may provide practical benefits to producers. Five trials were conducted to compare nursery phase-feeding programs. Two treatments consisting of a 2-phase or a single-phase program were applied for 22 d postweaning. The 2-phase program consisted of a feed budget of 1.4 kg of a phase 1 diet formulated with 1.45% SID Lys and 5.4 kg of a phase 2 diet with 1.36% SID Lys. The single-phase program provided 6.8 kg of a unique diet with 1.38% SID Lys. Diets were corn, soybean meal, and whey permeate-based and contained 3,000 mg/kg Zn. All other nutrients met or exceeded the NRC (2012) recommendations. After the experimental period, pigs were fed a common diet for 23 d. In the five trials, 5,090 pigs were used with a total of 63 and 69 replicates per treatment for 2-phase and single-phase programs, respectively. There was no treatment × trial interactions (P > 0.10), thus data was combined for statistical analysis using SAS PROC MIXED. From d 0 to 22, pigs fed the single-phase program had higher (P = 0.041) ADFI and a tendency (P = 0.075) for higher BW. From d 22 to 45, pigs previously fed the single-phase program had a tendency (P = 0.057) for higher ADG. Overall (d 0 to 45), pigs fed the single-phase program had higher (P = 0.037) ADG and a tendency (P = 0.077) for higher final BW, with comparable (P > 0.10) ADFI and G:F to the 2-phase program. In conclusion, feeding a single-phase nursery program in the first 22 d postweaning resulted in higher overall ADG and similar ADFI and G:F compared to a 2-phase nursery program.

A 20-d experiment was conducted to evaluate the effects of added Zn and Cu on growth performance of nursery pigs. Treatments were arranged in a 2 × 2 factorial treatment structure with main effects of added Zn (100 or 3,000 mg/kg of diet) and Cu (10 or 200 mg/kg of diet). Basal Zn and Cu levels (100 and 10 mg/kg, respectively) were from organic sources, while the added high levels (2,900 and 190 mg/kg, respectively) were from Zn oxide and Cu hydroxychloride. A total of 784 pigs (PIC 337 × Camborough), initially 6.0 kg, were used with 7 replicates per treatment. Experimental diets were corn, soybean meal, and whey permeate-based and contained 1.38% SID Lys. Pigs were weighed and feed disappearance measured to calculate ADG, ADFI, and G:F. Data were analyzed with SAS MIXED procedure. From d 0 to 10, there was no evidence (P > 0.10) for interactive or main effects of Zn or Cu. From d 10 to 20 and overall (d 0 to 20), there was an interaction (P < 0.05) between Zn and Cu for G:F. From d 10 to 20, pigs fed 10 mg/kg added Cu had improved G:F when 3,000 mg/kg added Zn was fed; however, pigs fed 200 mg/kg added Cu had similar G:F regardless of added Zn level. There was no evidence (P > 0.10) for interaction for ADG or ADFI, indicating an additive Zn and Cu effect. Feeding 3,000 mg/kg added Zn or 200 mg/kg added Cu improved ADG, ADFI, and final BW with the highest performance observed when feeding both 3,000 mg/kg added Zn and 200 mg/kg added Cu. In summary, feeding high levels of Zn or Cu did not impact the first 10-d postweaning performance, but Zn and Cu effects were observed in the subsequent 10-d and overall performance.

Four experiments were conducted to determine the effects of increasing soybean meal (SBM) in diets with or without 25% DDGS on growth performance of nursery pigs. Treatments were arranged in a 2 × 3 factorial with main effects of SBM (27.5, 32.5, or 37.5%) and DDGS (0 or 25%). A total of 296, 2,502, 4,118, and 711 pigs, initially 10.6, 11.7, 12.5, and 12.3 kg, were used and there were 10, 16, 13, and 12 replicates per treatment in Exp. 1, 2, 3, and 4, respectively. Experimental diets were fed for 21 d. Pigs were weighed and feed disappearance measured to calculate ADG, ADFI, G:F, and caloric efficiency (CE). Data were analyzed using the GLIMMIX procedure of SAS with block as random effect and treatment as fixed effect. The average cull rate was 0.7, 0.5, 0.2, and 0% and the mortality rate was 0.7, 0.3, 0.4, and 0% in Exp. 1 to 4, respectively. There were interactions (P ≤ 0.039) between SBM and DDGS for G:F and CE in Exp. 2 and for ADG and ADFI in Exp. 3. These were mostly driven by increasing SBM negatively affecting performance in a greater magnitude when diets contained DDGS compared to diets without DDGS. The main effects of DDGS and SBM were more consistent across experiments. Pigs fed diets with 25% DDGS had decreased (P ≤ 0.001) ADG and ADFI in all experiments as well as poorer (P ≤ 0.028) G:F and CE except for Exp. 3. Feeding increasing amounts of SBM generally did not result in any major impact in ADG, but consistently improved (linear, P ≤ 0.078) G:F and CE across experiments. The mechanism for this response is unclear but could be driven by intrinsic components of SBM or underestimating the energy value of SBM.

Two experiments were conducted to determine the effects of a functional protein (FXP; Ani-Tek Group, LLC, Shelbina, MO) on growth performance of nursery pigs. A total of 840 pigs (PIC 337 × Camborough), initially 5.5 kg, were used with 28 pigs per pen and a total of 15 replicates per treatment. There were two treatments, which consisted of a control diet and the control diet with added FXP. The experimental diets were corn, soybean meal, and whey permeate-based and contained 3,000 mg/kg added Zn. The inclusion of FXP was 0.3% of the diet. Experimental diets were fed for 23 d, followed by a common corn and soybean meal-based diet from d 23 to 48. Pigs were weighed and feed disappearance measured to calculate ADG, ADFI, and G:F. There was no evidence (P > 0.10) for treatment × experiment interactions, thus data was combined for statistical analysis using the MIXED procedure of SAS. From d 0 to 23, pigs fed diets containing FXP had higher (P < 0.05) ADG, ADFI, and BW and a tendency (P = 0.053) for improved G:F. During the common period (d 23 to 48), pigs previously fed FXP had a tendency (P < 0.10) for higher ADG and ADFI. Overall (d 0 to 48), pigs that received FXP had higher (P < 0.05) ADG, ADFI, BW, and a tendency (P = 0.055) for improved G:F. In conclusion, the inclusion of the functional protein improved growth performance of nursery pigs.

A 21-d experiment was conducted to estimate the energy value of soybean meal (SBM) and determine the effects of increasing SBM on pig performance. A total of 2,233 pigs (PIC 337 × 1050), initially 11.0 kg, were placed in pens containing 20 to 27 pigs. Treatments were assigned in a randomized complete block design with BW as blocking factor. Dietary treatments consisted of 21, 27, 33, or 39% SBM obtained by changing the amount of feed-grade amino acids and corn. There were 23 replicates per treatment. Pigs were weighed and feed disappearance measured to calculate ADG, ADFI, G:F, and caloric efficiency (CE). Cull pigs and mortality were evaluated daily. Data were analyzed with the GLIMMIX procedure of SAS. There was a tendency (P = 0.090) for a quadratic response for ADG, with a decrease in ADG observed with 39% SBM. There was a tendency (linear, P = 0.092) for a decrease in ADFI as SBM increased. Pigs fed diets with increasing SBM had a tendency (quadratic, P = 0.069) for an increase in G:F up to 33% SBM and an improvement (linear, P = 0.001; quadratic, P = 0.063) in CE with increasing SBM. There was no evidence for differences (P ≥ 0.457) in cull pigs and mortality. Using CE to estimate the energy of SBM relative to corn, a value of 105.4% of corn energy or 2,816 kcal/kg NE was determined using all data points. When removing the CE value of the 39% SBM treatment due to the quadratic tendency, SBM was estimated to have 121.1% of corn energy or 3,236 kcal/kg NE. The results suggest that feeding increasing levels of SBM improves G:F and CE. The energy value of SBM was estimated between 105 and 121% of corn, which is much greater than the NRC (2012) would suggest.

A total of 300 pigs (DNA 400 × 200, Columbus, NE), initially 11.1 kg, were used in a study to evaluate the effects of increasing amounts of high-protein distillers dried grains (HP DDG) on growth performance and to estimate its energy value relative to corn. Pigs were weaned, placed in pens with five pigs each, and fed a common diet for 21 d after weaning. Then, pens were assigned to treatments in a randomized complete block design. There were 5 treatments with 12 replicates per treatment. Treatments consisted of 0, 10, 20, 30, or 40% HP DDG, formulated by changing only the amounts of corn and feed-grade amino acids. Pigs were weighed weekly for 21 d to evaluate average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F). Caloric efficiency was obtained by multiplying ADFI by kcal of net energy (NE) per kg of diet and dividing by ADG. The NE values for corn and soybean meal were obtained from NRC (2012), and initial estimates for HP DDG NE were derived from the Noblet et al. (1994) equation. The energy of HP DDG was estimated based on caloric efficiency relative to the diet without HP DDG. Pigs fed diets with increasing HP DDG had a linear decrease (P < 0.01) in ADG, ADFI, and final body weight. There was a tendency for a quadratic response (P = 0.051) in G:F, with the greatest G:F observed for pigs fed diets with 40% HP DDG. There was a linear reduction (P < 0.05) in caloric efficiency with increasing amounts of HP DDG, indicating the initial NE estimate of HP DDG was underestimated. The use of caloric efficiency to estimate the energy value of HP DDG presents several limitations. This approach assumes that the NE values of corn and soybean meal are accurate and does not take into account possible changes in body composition, which can influence the G:F response as leaner pigs are more efficient. In conclusion, increasing HP DDG in the diet linearly decreased ADG and ADFI. Using caloric efficiency to estimate energy content relative to corn, the HP DDG used in this study was estimated to be 97.3% of the energy value of corn. Direct or indirect calorimetry is needed to confirm this value.

Background Two experiments were conducted to determine the effects of increasing amounts of soybean meal (SBM) in swine diets and estimate the energy value of SBM. Methods A total of 2233 pigs (PIC 337 × 1050, Hendersonville, TN) and 3796 pigs (PIC 359 × C40), initially 11.0 kg and 17.6 kg body weight (BW), were used in Exp. 1 and 2, respectively. In Exp. 1, pigs were placed in 92 pens each containing 20 to 27 pigs. In Exp. 2, pigs were placed in 84 pens each containing 37 to 43 pigs. Treatments were assigned in a randomized complete block design with BW as the blocking factor. Dietary treatments consisted of 21%, 27%, 33%, or 39% SBM in Exp. 1 and 17.5%, 22%, 26.5%, 31%, 35.5%, or 40% SBM in Exp. 2, obtained by changing the inclusion rate of feed-grade amino acids and corn grain. For Exp. 1, representative samples of corn grain, SBM, and distillers dried grains with solubles were analyzed for total AA content prior to diet formulation. For Exp. 2, diets were formulated using NRC (2012) nutrient loadings. Treatment diets were fed for 21 and 22 d (Exp. 1 and 2) and there were 23 replicates in Exp. 1 and 14 replicates in Exp. 2. Pigs were weighed and feed disappearance measured weekly to calculate average daily gain (ADG), average daily feed intake (ADFI), gain-to-feed ratio (G:F), and caloric efficiency (CE). Data were analyzed with block as a random effect and treatment as a fixed effect, and contrasts were constructed to test the linear and quadratic effects of increasing SBM. Results In Exp. 1, there was a tendency (linear, P = 0.092) for a decrease in ADFI as SBM increased. There was a tendency (P = 0.090) for a quadratic response for ADG, with a decrease in ADG observed with 39% SBM inclusion. Pigs fed diets with increasing SBM had a tendency (quadratic, P = 0.069) for an increase in G:F up to 33% SBM and an improvement (linear, P = 0.001; quadratic, P = 0.063) in CE with increasing SBM. Using CE to estimate the energy of SBM relative to corn, a value of 105.4% of corn energy or 2816 kcal/kg NE was determined using all data points. When removing the CE value of the 39% SBM treatment due to the quadratic tendency, SBM was estimated to have 121.1% of corn energy or 3236 kcal/kg NE. In Exp. 2, there was a decrease (linear, P = 0.001) in ADFI. Pigs fed increasing SBM had a tendency (linear, P = 0.065) for reduced ADG but an improvement (linear, P = 0.001) in G:F and CE as SBM increased. The energy value of SBM was estimated as 124.7% of corn energy or 3332 kcal/kg NE. Conclusions The results suggest that feeding increasing levels of SBM improves G:F and CE. The energy value of SBM was estimated to be between 105% and 125% of corn, which is much greater than the NRC (2012) would indicate.

Four experiments were conducted to determine the effects of increasing soybean meal (SBM) level in diets with or without 25% distillers dried grains with solubles (DDGS) on growth performance of nursery pigs raised in university or commercial facilities. Treatments were arranged in a 2 × 3 factorial with main effects of SBM (27.5%, 32.5%, or 37.5% of the diet) and DDGS (0% or 25% of the diet). A total of 296, 2,502, 4,118, and 711 pigs with initial body weight (BW) of 10.6, 11.7, 12.5, and 12.3 kg were used in Exp. 1, 2, 3, and 4, respectively. There were 10, 16, 13, and 12 replicates per treatment in Exp. 1, 2, 3, and 4, respectively. After weaning, pigs were fed common diets for approximately 21 d. Then, pens of pigs were assigned to treatments in a randomized complete block design with BW as the blocking factor and experimental diets were fed for 21 d. Pigs were weighed and feed disappearance measured to calculate average daily gain (ADG), average daily feed intake (ADFI), gain-to-feed ratio (G:F), and caloric efficiency (CE). Data were analyzed using the GLIMMIX procedure of SAS with block as a random effect and treatment as a fixed effect. Single degree-of-freedom contrasts were constructed to test the linear and quadratic effects of increasing SBM and their interactions with DDGS. Pigs used in all experiments did not undergo major health challenges during the experimental period and due to the low number of mortality and cull events, statistical analysis was not performed on these variables. The average cull rate was 0.7%, 0.5%, 0.2%, and 0%, and the mortality rate was 0.7%, 0.3%, 0.4%, and 0% in Exp. 1–4, respectively. There were interactions (P ≤ 0.039) between SBM and DDGS for G:F and CE in Exp. 2 and for ADG and ADFI in Exp. 3. These were mostly driven by increasing SBM negatively affecting performance in a greater magnitude when diets contained DDGS compared to diets without DDGS. The main effects of DDGS and SBM were more consistently observed across experiments. Pigs fed diets with 25% DDGS had decreased (P ≤ 0.001) ADG and ADFI in all experiments, as well as poorer (P ≤ 0.028) G:F and CE except for Exp. 3. Feeding increasing amounts of SBM generally did not result in any major impact in ADG but consistently improved (linear, P ≤ 0.078) G:F and CE across experiments.

An experiment was conducted to determine the effects of wheat middlings inclusion rate on growth performance of nursery pigs. A total of 1,750 pigs (initial BW = 6.0 kg), placed in pens with 35 pigs each, were used in a 39-d trial. There were 5 treatments consisting of 0, 5, 10, 15, or 20% wheat middlings. Corn and a fermented soybean meal product (ME-Pro, Prairie AquaTech, Brookings, SD) were replaced by wheat middlings to achieve the desired levels, whereas soybean meal inclusion rate was constant across treatments. Diets were not balanced for net energy. The experimental diets were fed from d 0 to 18 and a common corn-soybean meal-based diet was fed from d 18 to 39. There were 10 replicates per treatment. Pigs were weighed on d 0, 18, and 39 to calculate ADG, ADFI, and G:F. Data were analyzed with SAS MIXED procedure. From d 0 to 18, there was a linear (P = 0.041) reduction in ADG with increasing levels of wheat middlings; however, the differences were small (ranging from maximum 288 to minimum 275 g/d). This response was driven by a tendency (P = 0.096) for a linear ADFI response and a quadratic (P = 0.023) G:F response. From d 18 to 39, there was a linear (P = 0.016) G:F response, where pigs previously fed high levels of wheat middlings had improved G:F. Overall (d 0 to 39), there was no evidence (P > 0.10) for differences on growth performance. In conclusion, pigs fed high levels of wheat middlings had slightly decreased performance from d 0 to 18, but no evidence for differences were observed in the overall nursery period.

Histidine may be the sixth limiting amino acid (AA) in practical nursery diets supplemented with high amounts of feed-grade AA. Therefore, 2 experiments were conducted to determine the standardized ileal digestible (SID) His:Lys ratio requirement estimate for growth performance of 7- to 11-kg nursery pigs. A total of 360 and 350 pigs (DNA 241 × 600, Columbus, NE; initially 7.1 ± 0.31 and 6.6 ± 0.36 kg) were used in Exp. 1 and 2, respectively. There were 5 pigs per pen with 12 replicates per treatment in Exp. 1 and 10 replicates per treatment in Exp. 2. After weaning, pigs were fed a common pelleted diet for 10 d in Exp. 1 and 7 d in Exp. 2. Then, pens were assigned to treatments in a randomized complete block design with body weight (BW) as the blocking factor. Dietary treatments consisted of SID His:Lys ratios of 24%, 28%, 32%, 36%, 40%, and 44% in Exp. 1 and 24%, 28%, 30%, 32%, 34%, 36%, and 42% in Exp. 2. Experimental diets were fed in pellet form for 10 or 14 d in Exp. 1 and 2, followed by a common mash diet for 15 or 14 d, respectively. Data were analyzed using the GLIMMIX and NLMIXED procedures of SAS, fitting data with heterogeneous variance when needed. The competing statistical models utilized were quadratic polynomial, broken-line linear (BLL), and broken-line quadratic. In Exp. 1, increasing SID His:Lys ratio increased (quadratic, P = 0.001) ADG, ADFI, G:F, and day 10 BW. In Exp. 2, ADG, G:F, and day 14 BW increased (quadratic, P = 0.001), and ADFI increased linearly (P = 0.001) with increasing SID His:Lys ratio. The best-fitting model for all response variables analyzed was the BLL. In Exp. 1, requirement estimates were 29.7%, 29.1%, and 29.8% SID His:Lys ratio for ADG, ADFI, and G:F, respectively. In Exp. 2, the SID His:Lys ratio requirement estimates were 31.0% for ADG and 28.6% for G:F. These results suggest that the SID His requirement estimate for growth performance is no more than 31% of Lys and that the NRC (2012) SID His requirement of 34% of Lys may be overestimated for 7- to 11-kg pigs.

An experiment was conducted to determine the effects of Zn level and Ca source on nursery performance. Treatments were arranged in a 2 × 2 factorial with main effects of added Zn (100 or 3,000 mg/kg) and Ca source (limestone or Ca citrate). The basal level of Zn (100 mg/kg) was from organic source, whereas the 3,000 mg/kg was created with the inclusion of 2,900 mg/kg Zn oxide. A total of 3,701 pigs (PIC 337 × Camborough), initially 5.4 kg, were used with 18 replicates per treatment. Experimental diets were fed for 19 d, followed by a common diet from d 19 to 49. Pigs were weighed and feed disappearance measured to calculate ADG, ADFI, and G:F. Data were analyzed with SAS MIXED procedure. There were interactions (P < 0.05) between Zn and Ca for G:F from d 10 to 19 and 0 to 19. From d 10 to 19, feeding 3,000 mg/kg added Zn improved G:F with both Ca sources, but the magnitude of improvement was greater when diets contained Ca citrate. From d 0 to 19, only pigs fed Ca citrate presented improvement in G:F when fed 3,000 mg/kg added Zn. For main effects, feeding 3,000 mg/kg added Zn improved (P < 0.05) ADG and G:F from d 0 to 10. From d 10 to 19 and 0 to 19, feeding 3,000 mg/kg added Zn increased (P < 0.05) ADG and ADFI. During the common period (d 19 to 49), pigs previously fed 100 mg/kg added Zn had improved (P < 0.01) G:F. Overall (d 0 to 49), no differences (P > 0.10) in performance were observed. In conclusion, there were no major differences in performance between Ca sources. Pigs fed 3,000 mg/kg added Zn presented improved growth performance from d 10 to 19 but not overall.

An experiment was conducted to compare the effects of increasing dietary net energy (NE) in finishing pig diets while either maintaining a standardized ileal digestible lysine:NE ratio (SID Lys:NE) or maintaining SID Lys as a constant percentage of the diet across increasing energy densities. A total of 150 pigs (Line 600 × 241; DNA, Columbus, NE; initially 35.7 kg) were used in a 91-d study. Pigs were blocked by sex and weight and randomly assigned to 1 of 5 treatments with 2 pigs per pen and 15 pens per treatment. Treatments included a low-energy control diet that was corn-soybean meal-based with added soybean hulls, and a 2 × 2 factorial arrangement of treatments with main effects of increasing dietary NE (medium or high by adding choice white grease) and formulation method (with a SID Lys:NE ratio or maintaining the same percentage SID Lys). Linear and quadratic contrasts were made using the control diet and the medium- and high-energy diets within each formulation method. Pigs and feeders were weighed approximately every 30 d to calculate average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F). At the end of the experiment, pigs were sent to a commercial processing facility for carcass data collection. From days 0 to 34 and 34 to 61, ADG and SID Lys intake increased as NE increased (linear, P < 0.05) in pigs fed diets with a Lys:NE ratio, but not for those fed the same percentage Lys. As NE increased, NE intake and G:F increased (P < 0.01) in pigs fed diets with either formulation method. From days 61 to 91, increasing NE had no effect (P > 0.10) on ADG. There was no change in G:F in pigs fed diets with the same percentage Lys (P > 0.10), but G:F decreased then increased (quadratic, P < 0.01) in response to increasing NE in pigs fed diets with a SID Lys:NE ratio. Overall, increasing dietary NE increased (linear, P < 0.001) daily NE intake and G:F (linear, P < 0.018) with either formulation method. However, SID Lys intake, ADG, and hot carcass weight only increased (linear, P < 0.01) when a SID Lys:NE ratio was maintained. Increasing NE without maintaining a constant SID Lys:NE ratio increased backfat depth (quadratic, P = 0.01), whereas it did not in pigs fed diets with a SID Lys:NE ratio. In conclusion, increasing dietary energy density increased NE intake and G:F regardless of formulation method. However, a SID Lys:NE ratio must be maintained to achieve increased ADG and minimize fat deposition.

A total of 300 pigs (DNA 400×200; initially 11.1 kg) were used in a 21-d trial to determine the effects of increasing levels of high-protein distillers dried grains (HP DDG) on pig performance and to estimate the productive energy of HP DDG. Pens with 5 pigs each were assigned to treatments in a randomized complete block design with 12 replicates per treatment. Treatments included diets with 0, 10, 20, 30, or 40% HP DDG formulated by changing corn and feed-grade amino acid levels. Caloric efficiency was obtained by multiplying ADFI by dietary net energy (NE) and dividing by ADG. The NE of HP DDG was estimated at 1,914 kcal/kg by using Noblet et al. (1994) equation and NRC (2012) values were used for corn. Productive energy was estimated based the average caloric efficiency of the HP DDG diets relative to the diet without HP DDG. Data were analyzed with the GLIMMIX procedure of SAS with pen as the experimental unit and block as random effect. Pigs fed diets with increasing HP DDG had a linear decrease (P < 0.01) in ADG and ADFI and a tendency (P = 0.051) for a quadratic response in G:F. There was a linear improvement (P < 0.01) in caloric efficiency with increasing HP DDG (3,876, 3,753, 3,676, 3,520, and 3,300 kcal/kg, respectively). The productive energy of HP DDG was estimated as 2,686 kcal/kg or 97.3% of corn NE. In summary, high levels of HP DDG negatively impacted growth performance. The equation used to estimate NE of HP DDG resulted in underestimated values. The productive energy of HP DDG is approximately 97% of corn NE.

A total of 3,171 pigs (PIC 327×L42; initially 5.8 kg) were used in a 39-d study. Treatments were arranged in a 2 × 2 factorial with 0 or 1% cellulose (Arbocel, J. Rettenmaier USA, Schoolcraft, MI) and distillers dried grains with solubles (DDGS; 0 or 5% in phase 1 and 0 or 15% in phase 2). Dietary phases 1 and 2 were offered from d 0 to 10 and 10 to 25, respectively. From d 25 to 39, pigs received a common diet with 25% DDGS. Pens were blocked by weight and allotted to treatments in a randomized complete block design. Experimental unit was two pens (66 pigs) sharing a fence-line feeder with 12 replicates per treatment. Data were analyzed with the GLIMMIX procedure of SAS with block as random effect. From d 0 to 25 and d 0 to 39, there was an interaction (P < 0.05) between cellulose and DDGS for ADG. Pigs fed diets with both DDGS and cellulose had lower ADG than those fed diets without DDGS, with pigs fed diets with DDGS without the addition of cellulose being intermediate. From d 25 to 39, there was a tendency (P = 0.080) for an interaction for ADFI. Pigs previously fed diets without DDGS and with cellulose had higher ADFI than those fed diets with DDGS and cellulose, and pigs previously fed diets without cellulose had similar ADFI regardless of DDGS inclusion. There was a tendency for an interaction (P = 0.070) for pig removals. Adding cellulose to diets without DDGS numerically decreased pig removals, but the inclusion of cellulose to diets with DDGS resulted in increased pig removals. In summary, adding fiber to the diet as cellulose or DDGS resulted in a less pig removals; however, adding both cellulose and DDGS decreased ADG and ADFI.

Two experiments were conducted to determine the effects of soybean meal (SBM) level in diets with or without distillers dried grains with solubles (DDGS) on growth performance of late nursery pigs. A total of 1,064 and 1,011 pigs (PIC 280×1050; initially 10.5 ± 0.36 and 10.9 ± 0.22 kg) were used in Exp. 1 and 2, respectively, with 21 to 27 pigs per pen. Pens were assigned to treatments in a randomized complete block design with 7 replicates per treatment per experiment. Treatments 1 to 3 were diets with 23% DDGS and 21, 27, or 35% SBM. Treatments 4 and 5 were corn-SBM diets with 27 or 35% SBM. Diets were balanced to 1.30% standardized ileal digestible lysine and 2,606 kcal of net energy/kg. Data were analyzed with the GLIMMIX procedure of SAS with pen as the experimental unit and block as random effect. There was no evidence for treatment × experiment interactions, thus data from both trials were combined. Feeding diets with 23% DDGS decreased (P = 0.033) ADFI and improved (P = 0.033) G:F compared to corn-SBM diets, which may indicate underestimation of DDGS net energy. When analyzed as a factorial with or without DDGS, pigs fed diets with 35% SBM had a tendency (P = 0.052) for increased ADG and improved (P = 0.001) G:F compared with diets with pigs fed 27% SBM. As SBM increased from 21 to 35% in diets with DDGS, ADG (linear, P = 0.001) and G:F (quadratic, P = 0.007) improved. In summary, feeding diets with increasing SBM improved growth performance in late nursery pigs.

Excess of a branched-chain amino acid (BCAA), particularly Leu, may result in increased degradation of the others due to common catabolic steps. Moreover, large neutral amino acids (LNAA) and BCAA have common brain transporters. Therefore, excessive BCAA may decrease the absorption of AA that serve as precursors of neurotransmitters. We hypothesize that practical diets with high levels of feed-grade AA can potentially create BCAA imbalances and impact performance. A meta-regression was conducted to evaluate the effects of BCAA and their interactions with LNAA to develop prediction equations for ADG, ADFI, and G:F. Data from 25 papers for a total of 44 trials were recorded in a database. Diets were reformulated using NRC (2012) nutrient values. Amino acids were expressed on standardized ileal digestible basis. A step-wise manual forward selection was used to evaluate predictor variables. Predictors had to be significant (P < 0.05) as a single variable predictor and provide a BIC improvement of at least 2 points to be included in the model. Observations were weighted using the inverse of the squared SEM. The resulting predictor equations were: ADG, g = – 985.94 + (15.2499 × average BW (kg)) – (0.08885 × average BW × average BW) + (1.063 × Leu:Lys) + (20.2659 × Ile:Lys) – (0.1479 × Ile:Lys × Ile:Lys) + (9.2243 × (Ile+Val):Leu) – (0.03321 × (Ile+Val):Leu × (Ile+Val):Leu) – (0.4413 × Ile:Trp); G:F = 648.3 – (6.2974 × average BW (kg)) + (0.02051 × average BW × average BW) + (0.5396 × Ile:Lys) + (1.7284 × Val:Lys) – (0.00795 × Val:Lys × Val:Lys) – (1.7594 × Met:Lys); and ADFI, kg = predicted ADG/predicted G:F. The equations suggest that increasing Leu:Lys negatively affects ADG due to a reduction in ADFI and G:F. The addition of Val, Ile, and Trp, alone or in combination, has the potential to counteract the negative effects of high Leu on growth performance.

An experiment was conducted to determine the effects of added Zn source and level on growth performance and carcass characteristics of finishing pigs. A total of 1,980 pigs divided into 2 groups [group 1: 1,008 pigs, TR4 × (Fast Large White × PIC L02) and group 2: 972 pigs, PIC 337 × 1,050], initially 33.3 kg, were used in a 103- or 114-d growth trial in groups 1 and 2, respectively. Treatments were arranged in a 2 × 3 factorial with 2 sources of added Zn, Zn hydroxychloride (ZnHyd; IntelliBond Z, Micronutrients, Indianapolis, IN) or Zn sulfate (ZnSO4), and 3 levels of added Zn (50, 100, or 150 mg/kg). Diets contained a vitamin-trace mineral premix without added Zn and provided 76 and 162 mg/kg Fe and Cu, respectively. All diets contained 750 FTU/kg phytase. There was a total of 14 replicates per treatment. Pens of pigs were weighed approximately every 2 wk to determine average daily gain (ADG), average daily feed intake, and gain-to-feed ratio. At the end of the experiment, pigs were transported to a packing plant to determine hot carcass weight (HCW), backfat depth, loin depth, and lean percentage. Overall, there was no evidence (P > 0.10) for interactive effects of added Zn source and level for growth performance and carcass characteristics. Pigs fed diets with increasing added Zn had a tendency (P = 0.093) for a quadratic response in ADG, with the greatest ADG observed at 100 mg/kg added Zn. There was a linear improvement (P = 0.010) in carcass yield and a quadratic response (P = 0.045) in HCW, with pigs fed 100 mg/kg added Zn having the highest HCW. Pigs fed diets with ZnHyd had improved (P = 0.017) carcass yield and a tendency (P = 0.058) for greater HCW compared with pigs fed ZnSO4. In summary, under the commercial conditions of the study and with diets containing 750 FTU/kg phytase, there were relatively small improvements in ADG of growing-finishing pigs fed added Zn beyond 50 mg/kg. Providing higher levels of added Zn improved carcass characteristics. Zinc source did not influence growth performance, but ZnHyd improved carcass characteristics compared with ZnSO4.

Two experiments were conducted to determine the effects of trace mineral source and level for grow-finish pigs. In Exp. 1, 2,168 pigs (initial BW = 23.0 kg) were used in a 117-d trial. There were 5 treatments based on inorganic (sulfates and oxides) or organic (Alltech Bioplex, Lexington, KY) minerals supplemented at different levels as follows: 1) Industry inorganic (120 mg/kg Zn, 100 mg/kg Fe, 40 mg/kg Mn, 10 mg/kg Cu); 2) 100% NRC inorganic (60 mg/kg Zn, 60 mg/kg Fe, 2.2 mg/kg Mn, 4 mg/kg Cu); 3) 33% NRC organic (20 mg/kg Zn, 20 mg/kg Fe, 0.7 mg/kg Mn, 1.3 mg/kg Cu); 4) 66% NRC organic (40 mg/kg Zn, 40 mg/kg Fe, 1.5 mg/kg Mn, 2.6 mg/kg Cu); and 5) 100% NRC organic (60 mg/kg Zn, 60 mg/kg Fe, 2.2 mg/kg Mn, 4 mg/kg Cu). Selenium level was 0.30 mg/kg for all treatments. Treatment 1 had 14 replicates and the other treatments had 18 replicates. Pigs were weighed approximately every three weeks and carcass data was collected at the end of the trial. Data was analyzed with SAS MIXED procedure. There was no evidence for differences (P > 0.10) for overall ADG, ADFI, G:F, and final BW. Pigs fed 66% NRC organic had the highest (P < 0.05) percentage lean and loin depth. In Exp. 2, 1,188 pigs (initial BW = 25.9 kg) were used in a 120-d trial with two treatments: 1) Industry inorganic and 2) 66% NRC organic, with the same mineral levels as Exp. 1 and 24 replicates per treatment. There was no difference (P > 0.10) in growth performance. Similar to Exp. 1, pigs fed 66% NRC organic had higher (P < 0.05) percentage lean and loin depth. In conclusion, lower levels of organic trace minerals resulted in improved carcass characteristics without compromising growth performance.

Excess dietary leucine stimulates the key enzymes involved in branched-chain catabolism causing breakdown of all branched-chain amino acids, including isoleucine and valine. Branched-chain amino acids share a common brain transporter with other large neutral amino acids (LNAA). Excess levels of one of the LNAA increases brain uptake of that amino acid and decreases the uptake of the other LNAA, including tryptophan. Thus, excess leucine can impact the requirements for many amino acids. From a practical basis, this effect was first demonstrated with diets containing blood meal, but was thought to be of limited concern unless high blood meal diets were fed. Use of corn dried distillers grains with solubles (DDGS) or high protein DDGS in corn-based diets results in diets containing excess leucine. These high leucine levels are of limited concern if adequate levels of other branched-chain amino acids and LNAA are fed, which is often the case if the diet consists largely of intact protein sources. Feed grade amino acids, such as L-lysine, L-threonine, L-tryptophan, DL-methionine, L-valine, and L-isoleucine have been widely adopted as a means to lower nitrogen excretion and diet cost. Including these amino acids in diets containing corn products reduces dietary leucine; but the resulting diets are formulated near the requirement for the first 6 limiting amino acids, including valine, isoleucine, and tryptophan, while still being high in leucine. The excess leucine increases the requirements for valine, isoleucine, and possibly other LNAA, such as tryptophan and possibly others. The exact relationship between these amino acids and how to handle them in practical diet formulation is still being elucidated; however, recent meta-analysis and experimental data confirm the importance of these ratios and provide useful direction for future research.

A previous study conducted by our group determined that the standardized ileal digestible (SID) His:Lys ratio requirement for 7- to 11-kg pigs ranged from 29.1 to 29.8%. The objective of this study was to validate the SID His:Lys ratio requirement by creating treatments more closely spaced around the expected requirement. A total of 350 pigs (DNA 600 × 241, initially 6.6 ± 0.36 kg) were used in a 14-d study. There were 10 replicates per treatment and 5 pigs per pen. Pens were blocked by weight and assigned to 1 of 7 dietary treatments containing 24, 28, 30, 32, 34, 36, or 42% SID His:Lys ratios in a randomized complete block design. Dietary SID Lys was 1.25% and all other amino acids met or exceeded the NRC (2012) requirement estimates. Diets were corn, spray-dried whey, and whey protein concentrate-based and treatments were formed by adding crystalline L-His at the expense of corn. Response variables ADG, ADFI, and G:F were fitted using general linear and nonlinear mixed models with heterogeneous variances and pen as the experimental unit. Competing models included quadratic polynomial, broken-line linear, and broken-line quadratic. For each response variable, the best fitting model was selected based on Bayesian Information Criterion. Increasing SID His:Lys ratio resulted in a linear increase (P < 0.01) in ADFI and quadratic responses (P < 0.01) in ADG and G:F. The response for ADFI was not modeled due to its linear nature. The best fitting model for ADG and G:F was the broken-line linear. For ADG, the requirement was estimated at 31.0% SID His:Lys (95% CI: 29.7 to 32.3%). The maximum mean G:F was obtained at 28.6% SID His:Lys (95% CI: 27.1 to 30.0%). In conclusion, the estimated SID His requirement for 7- to 11-kg pigs is no more than 31% of Lys. [Image: see text]

Histidine may be the sixth limiting amino acid (AA) in practical nursery diets supplemented with high amounts of feed-grade AA. Therefore, 2 experiments were conducted to determine the standardized ileal digestible (SID) His:Lys ratio requirement estimate for growth performance of 7- to 11-kg nursery pigs. A total of 360 and 350 pigs (DNA 241 × 600, Columbus, NE; initially 7.1 ± 0.31 and 6.6 ± 0.36 kg) were used in Exp. 1 and 2, respectively. There were 5 pigs per pen with 12 replicates per treatment in Exp. 1 and 10 replicates per treatment in Exp. 2. After weaning, pigs were fed a common pelleted diet for 10 d in Exp. 1 and 7 d in Exp. 2. Then, pens were assigned to treatments in a randomized complete block design with body weight (BW) as the blocking factor. Dietary treatments consisted of SID His:Lys ratios of 24%, 28%, 32%, 36%, 40%, and 44% in Exp. 1 and 24%, 28%, 30%, 32%, 34%, 36%, and 42% in Exp. 2. Experimental diets were fed in pellet form for 10 or 14 d in Exp. 1 and 2, followed by a common mash diet for 15 or 14 d, respectively. Data were analyzed using the GLIMMIX and NLMIXED procedures of SAS, fitting data with heterogeneous variance when needed. The competing statistical models utilized were quadratic polynomial, broken-line linear (BLL), and broken-line quadratic. In Exp. 1, increasing SID His:Lys ratio increased (quadratic, P = 0.001) ADG, ADFI, G:F, and day 10 BW. In Exp. 2, ADG, G:F, and day 14 BW increased (quadratic, P = 0.001), and ADFI increased linearly (P = 0.001) with increasing SID His:Lys ratio. The best-fitting model for all response variables analyzed was the BLL. In Exp. 1, requirement estimates were 29.7%, 29.1%, and 29.8% SID His:Lys ratio for ADG, ADFI, and G:F, respectively. In Exp. 2, the SID His:Lys ratio requirement estimates were 31.0% for ADG and 28.6% for G:F. These results suggest that the SID His requirement estimate for growth performance is no more than 31% of Lys and that the NRC (2012) SID His requirement of 34% of Lys may be overestimated for 7- to 11-kg pigs.

Lysine is the first limiting amino acid in swine diets, thus providing the appropriate level in the diet is critical to growth performance. Therefore, the objective of this study was to determine the standardized ileal digestible (SID) Lys requirement of nursery pigs from 15 to 35 lb. A total of 300 maternal line barrows (200 × 400, DNA, Columbus, NE; initially 14.9 ± 0.5 lb BW) were fed six experimental diets as part of a 21-d trial. Pigs were randomly allotted to pens at weaning based on BW, and were fed a common pelleted diet for 9 d after weaning. Pens were then randomly assigned to dietary treatments (10 pens/treatment with 5 pigs/pen) based on average pig weight. The six dietary treatments had increasing SID Lys (1.05, 1.15, 1.25, 1.35, 1.45, and 1.55%) and were achieved by increasing the inclusion of crystalline AA, allowing soybean meal to stay constant across dietary treatments. Experimental data were analyzed using general linear and non-linear mixed models with heterogeneous residual variances. Competing models included linear (LM), quadratic polynomial (QP), broken-line linear (BLL), and broken-line quadratic (BLQ). For ADG, F/G, and IOFC, the best-fitting model was selected using Bayesian information criterion. Overall, increasing SID Lys improved (linear, P 1.55%) SID Lys, respectively. For F/G, the best-fitting model was the LM where F/G was improved up to at least 1.55% SID Lys. For income over feed cost (IOFC), the best-fitting model was the BLL, in which the maximum mean IOFC was estimated at 1.25% (95% CI: 1.14, 1.36%). In conclusion, the estimated SID Lys required for maximum mean ADG of these maternal line barrows was lower than the estimated mean SID Lys required for maximum mean F/G. This study provides evidence that different response variables can result in different estimates of the requirements; however, at least 1.25% SID Lys was needed to maximize IOFC.

As exigências de lisina durante a gestação, para o ganho de reservas corporais maternas e peso ao nascer dos leitões, não estão bem estabelecidas nos genótipos contemporâneos prolífi cos. Este estudo objetivou avaliar o efeito da suplementação de lisina no terço fi nal da gestação, sobre o peso ao nascer dos leitões e o desempenho gestacional e lactacional de leitoas. Leitoas prenhes foram uniformemente distribuídas em dois grupos que receberam, dos 85 aos 110 dias de gestação, diferentes níveis de lisina na dieta: Grupo Controle – 28g lisina/dia (n=136), e Grupo Lisina – 35g lisina/dia (n=141). Não houve efeito (P>0,10) da suplementação de lisina no ganho de peso e espessura de toucinho (ET) das fêmeas e no peso dos leitões ao nascer. Leitoas suplementadas com lisina tenderam a ter menor percentagem de natimortos (P=0,077), menor variação de peso dentro da leitegada (P= 0,094) e menor percentagem de leitões pesando menos que 1100g (P=0,082), em comparação ao grupo controle. Durante a lactação, o desempenho das fêmeas e das leitegadas foi avaliado em um subgrupo de fêmeas (n=26/grupo). Não houve diferença entre os grupos Controle e Lisina (P>0,10) no consumo voluntário de ração, perdas de reservas corporais (peso e ET), intervalo desmame-estro das fêmeas e peso da leitegada ao desmame. Em conclusão, um incremento de lisina (de 28 para 35g dia-1) no terço fi nal da gestação de leitoas (85 até 110 dias) tende a reduzir o número de natimortos e aumentar a uniformidade do peso dos leitões ao nascer, mas não afeta o desempenho das fêmeas até o parto ou na fase lactacional subsequente. Lysine requirements for gain in maternal body reserves and piglet birth weight, during pregnancy, in contemporary prolifi c genotypes, are not well established. This study aimed to evaluate the effect of dietary lysine in late pregnancy on piglet birth weight, and on the gestational and lactational performance of gilts. Pregnant gilts were uniformly distributed into two groups and received, from 85 to 110 days of gestation, either of two lysine levels in their diet: Control group - 28g lysine/day (n=136), and Lysine group - 35g lysine/day (n=141). There were no effects (P>0.10) of supplemental lysine on body weight and backfat (BF) gain of females or on piglet birth weight. Gilts supplemented with lysine tended to have a lower percentage of stillbirths (P=0.077), reduced within-litter birth weight variation (P=0.094) and a lower percentage of piglets weighing less than 1100g (P=0.082) than in the Control group. During lactation, the performance of sows and litters was also evaluated in a subgroup of sows (n=26/group). There were no differences between the Control and Lysine groups (P>0.10) in voluntary feed intake, body reserve losses (weight and BF), weaning-to-estrus interval of the sows, and litter weaning weight. In conclusion, an increase in lysine (from 28 to 35g/day) in late gestation of gilts (85 to 110 days) tends to reduce the rate of stillbirths and to improve the uniformity of litter weight at birth, but does not affect the performance of females until farrowing or during subsequent lactation.