Effects of Added Zinc on Skeletal Muscle Morphometrics and Gene Expression of Finishing Pigs Fed Ractopamine-HCL.

Finishing pigs (n = 320) were used in a 35-day study to determine the effects of ractopamine-HCl (RAC) and supplemental Zinc (Zn) level on loin eye area (LEA) and gene expression. Pens were randomly allotted to the following treatments for the final 35 days on feed: a corn-soybean meal diet (CON), a diet with 10 ppm RAC (RAC+), and RAC diet plus added Zn at 75, 150, or 225 ppm. Sixteen pigs per treatment were randomly selected for collection of serial muscle biopsies and carcass data on day 0, 8, 18, and 32 of the treatment phase. Compared to CON carcasses, RAC+ carcasses had 12.6% larger (P = 0.03) LEA. Carcasses from RAC diets with added Zn had a tendency for increased (quadratic, P < 0.10) LEA compared to the RAC+ carcasses. Compared to RAC+ pigs, relative expression of IGF1 decreased with increasing levels of Zn on day 8 and 18 of treatment, but expression levels were similar on day 32 due to Zn treatments increasing in expression while the RAC+ treatment decreased (Zn quadratic × day quadratic, P = 0.04). A similar trend was detected for the expression of ß1-receptor where expression levels in the RAC+ pigs were greater than Zn supplemented pigs on day 8 and 18 of the experiment, but the magnitude of difference between the treatments was reduced on day 32 due to a decrease in expression by RAC+ pigs and an increase in expression by the Zn pigs (Zn quadratic × day quadratic, P = 0.01). The ability of Zn to prolong the expression of these two genes may be responsible for the tendency of Zn to increase LEA in RAC supplemented pigs.

The effects of feeding sorghum dried distillers grains with solubles on finishing pig growth performance, carcass characteristics, and fat quality.

The objective of this study was to determine the effects of feeding sorghum dried distillers grains with solubles (DDGS) in grain sorghum­ or corn-based diets on pig growth performance, carcass characteristics, and carcass fat quality. A total of 288 finishing pigs (BW 58.8 ± 4.43 kg; Line TR 4 × 1050, PIC, Hendersonville, TN) were used in a 73-d study. Pigs were allotted to 1 of 6 dietary treatments with 6 pens of 8 pigs per treatment. Treatments included grain sorghum­based diets with 0%, 15%, 30%, or 45% sorghum DDGS (29.0% CP, 7.2% ether extract); a grain sorghum­based diet with 30% corn DDGS (25.7% CP, 8.7% ether extract); and a corn-based diet with 30% corn DDGS. The diets were formulated to 0.95%, 0.83%, and 0.71% standardized ileal digestible Lys in phases 1, 2, and 3, respectively, and were not balanced for energy. On d 73, a subsample of 72 pigs (1 barrow and 1 gilt/pen) was harvested at Kansas State University's Meats Laboratory. Carcass traits were calculated, as well as 10th-rib LM color, marbling and firmness, and fat color score. Fat samples from the 10th rib were collected and analyzed for fatty acid profile, which was used to calculate iodine value (IV). The remaining pigs were transported to a commercial packing plant (Triumph Foods, St. Joseph, MO) for carcass measurement and jowl IV determinations. Overall, increasing the dietary sorghum DDGS reduced (linear, P < 0.01) ADG and increased (linear, P < 0.01) back fat IV. Pigs fed increasing sorghum DDGS had decreased 10th-rib fat a* (less red) and b* (less yellow; P < 0.01 and 0.06, respectively). No differences were observed in growth performance or back fat IV among pigs fed corn- or grain sorghum­based diets with 30% corn DDGS. Pigs fed the grain sorghum­based diet with 30% corn DDGS had fat color that was more yellow (b*; P < 0.03) than that of pigs fed the grain sorghum­based diet with 30% sorghum DDGS. Pigs fed the grain sorghum­based diet with 30% sorghum DDGS also had decreased back fat IV (P < 0.01) and fat that was whiter (L*; P < 0.02) than that of those fed the grain sorghum­based diet with corn DDGS. Pigs fed grain sorghum with 30% sorghum DDGS had lower (P < 0.01) back fat IV than pigs fed corn with 30% corn DDGS. Feeding a grain sorghum­based diet with increasing sorghum DDGS reduces ADG when diets are not balanced for energy but, when fed at 30% of the diet, produces firmer pork fat than feeding a corn-based diet with 30% corn DDGS, which may be preferred for pork export markets.

The effects of deoxynivalenol-contaminated corn dried distillers grains with solubles in nursery pig diets and potential for mitigation by commercially available feed additives.

Four experiments were conducted to investigate the effects of deoxynivalenol (DON) from naturally contaminated dried distillers grains with solubles (DDGS) and the efficacy of feed additives in nursery pig diets. In Exp. 1, 180 pigs (10.3 ± 0.2 kg BW) were fed 1 of 5 diets for 21 d. Diets were 1) Positive Control (PC; < 0.5 mg/kg DON), 2) Negative Control (NC; 4 mg/kg DON), 3) NC + 0.10% Biofix (Biomin Inc., Herzogenburg, Austria), 4) NC + 0.15% Cel-can (VAST Inc., Mason City, IA) and 0.50% bentonite clay, and 5) NC + 0.25% Defusion Plus (Cargill Animal Nutrition, Minneapolis, MN). Pigs fed the NC diet had poorer ( < 0.01) ADG than those fed the PC. Pigs fed Defusion Plus had improved ( < 0.03) ADG over those fed NC, whereas pigs fed Biofix or Cel-can with bentonite clay had reduced ADG ( < 0.01) compared with those fed PC. In Exp. 2, 340 pigs (11.7 ± 0.1 kg BW) were fed 1 of 8 diets for 21 d. Diets were 1) PC (< 0.5 mg/kg DON), 2) Low NC (1.5 mg/kg DON), 3) Low NC + 0.15% Biofix, 4) Low NC + 0.30% Biofix, 5) High NC (3.0 mg/kg DON), 6) High NC + 0.30% Biofix, 7) High NC + 0.45% Biofix, and 8) Diet 7 with 5% added water. Increasing the DON level reduced (linear; < 0.05) ADG, ADFI, and pig BW, and Biofix did not improve performance. In Exp. 3, 1,008 pigs (12.5 ± 0.3 kg BW) were fed 6 treatments for 24 d. Diets were 1) PC ( < 0.5 mg/kg DON), 2) NC (3 mg/kg DON), 3) NC + 0.25% Defusion, 4) NC + 0.50% Defusion, 5) Diet 3 with supplemental nutrients, and 6) Diet 5, pelleted. Pigs fed the NC had decreased ( < 0.01) ADG and ADFI, but adding Defusion improved (linear; < 0.04) ADG and ADFI over pigs fed NC. Pelleting improved ( < 0.01) both ADG and G:F, resulting in ADG above PC pigs. In Exp. 4, 980 pigs (12.0 ± 0.3 kg BW) were fed 1 of 7 diets in a 28-d trial in a 2 × 3 + 1 factorial arrangement. The 7 treatments were based on 3 diets fed in meal or pellet form: 1) PC (< 0.5 mg/kg DON), 2) NC (3 mg/kg DON), and 3) NC + 0.25% Defusion. Treatment 7 was Diet 3 with supplemental nutrients in pellet form. No interactions were observed between pelleting and Defusion. Pigs fed the NC had decreased ( < 0.01) ADG and ADFI, and pelleting improved ( < 0.01) ADG to PC levels, driven by improved ( < 0.01) G:F. Adding nutrients or Defusion had no effect. Overall, these studies show that Defusion and pelleting can help overcome some of the negative effects of DON, whereas other feed additives and additional nutrients do not.

Equations generated to predict iodine value of pork carcass back, belly, and jowl fat.

Data from existing literature were used to generate equations to predict finishing pig back, belly, and jowl fat iodine values (IV) and an experiment was conducted to evaluate these equations. The final database included 24, 21, and 29 papers for back, belly, and jowl fat IV, respectively. For experiments that changed dietary fatty acid composition, initial (INT) diets were defined as those fed before the change in diet composition and final (FIN) diets were those fed after. The predictor variables tested were divided into 5 groups: 1) diet fat composition (dietary percent C16:1, C18:1, C18:2, C18:3, EFA, unsaturated fatty acids, and IV product) for both INT and FIN diets, 2) day feeding the INT and FIN diets, 3) ME or NE of the INT and FIN diet, 4) live performance criteria (initial BW, final BW, ADG, ADFI, and G:F), and 5) carcass criteria (HCW and backfat thickness). The PROC MIXED procedure of SAS (SAS Inst., Inc., Cary, NC) was used to develop regression equations. Evaluation of models with significant terms was then conducted based on the Bayesian information criterion. The optimum equations to predict back, belly, and jowl fat IV were backfat IV = 84.83 + (6.87 × INT EFA) - (3.90 × FIN EFA) - (0.12 × INT days) - (1.30 × FIN days) - (0.11 × INT EFA × FIN days) + (0.048 × FIN EFA × INT days) + (0.12 × FIN EFA × FIN days) - (0.0060 × FIN NE) + (0.0005 × FIN NE × FIN days) - (0.26 × backfat depth); belly fat IV = 106.16 + (6.21 × INT EFA) - (1.50 × FIN days) - (0.11 × INT EFA × FIN days) - (0.012 × INT NE) + (0.00069 × INT NE × FIN days) - (0.18 × HCW) - (0.25 × backfat depth); and jowl fat IV = 85.50 + (1.08 × INT EFA) + (0.87 × FIN EFA) - (0.014 × INT days) - (0.050 × FIN days) + (0.038 × INT EFA × INT days) + (0.054 × FIN EFA × FIN days) - (0.0066 × INT NE) + (0.071 × INT BW) - (2.19 × ADFI) - (0.29 × backfat depth). Dietary treatments from the evaluation experiment consisted of a corn-soybean meal control diet with no added fat or a 3 × 3 factorial arrangement with main effects of fat source (4% tallow, 4% soybean oil, or a blend of 2% tallow and 2% soybean oil) and feeding duration (d 0 to 42, 42 to 84, or 0 to 84). The back, belly, and jowl fat IV equations tended to overestimate IV when observed IV were less than approximately 65 g/100 g and underestimate belly fat IV when actual IV are greater than approximately 74 g/100 g or when the fat blend was fed from d 0 to 84 or 42 to 84. Overall, with the exceptions noted, the regression equations were an accurate tool for predicting carcass fat quality based on dietary and pig performance factors.

Effect of added zinc in diets with ractopamine hydrochloride on growth performance, carcass characteristics, and ileal mucosal inflammation mRNA expression of finishing pigs.

Two experiments were conducted to determine the effects of increasing the dietary Zn content on growth performance, carcass characteristics, plasma Zn, and ileal mucosal inflammation mRNA expression of finishing pigs fed diets containing ractopamine HCl (RAC; Elanco Animal Health, Greenfield, IN). In Exp. 1, 312 pigs (327 × 1050; PIC, Hendersonville, TN; 94 kg BW) were used in a 27-d study. There were 2 pigs per pen and 26 pens per treatment. Treatments included a corn-soybean meal diet (control; 0.66% standardized ileal digestible [SID] Lys); a diet (0.92% SID Lys) with 10 mg/kg RAC; and the RAC diet plus 50, 100, or 150 mg Zn/kg from ZnO or 50 mg Zn/kg from a Zn AA complex (ZnAA; Availa-Zn; Zinpro, Eden Prairie, MN). All diets also contained 83 mg Zn/kg from ZnSO4 in the trace mineral premix. Pigs fed the RAC diet without added Zn had increased (P < 0.05) ADG, G:F, HCW, carcass yield, and loin weight compared with pigs fed the control diet. Increasing Zn from ZnO in diets containing RAC tended to increase (linear, P = 0.067) G:F and loin weight (quadratic, P = 0.064). Pigs fed diets with 50 mg Zn/kg from ZnAA tended to have increased (P = 0.057) ADG compared with pigs fed the RAC diet. In Exp. 2, 320 pigs (327 × 1050; PIC; 98 kg BW) were used in a 35-d study. There were 2 pigs per pen and 20 pens per treatment. Treatments included a control diet (0.66% SID Lys); a diet (0.92% SID Lys) with 10 mg/kg RAC; or the RAC diet plus 75, 150, and 225 mg Zn/kg from ZnO or ZnAA. All diets also contained 55 mg Zn/kg from ZnSO4 from the trace mineral premix. Pigs fed the RAC diet had increased (P < 0.05) ADG, G:F, HCW, loin depth, percentage lean, and liver weight compared with pigs fed the control diet. No Zn level or source effects or level × source interactions were observed for growth performance. A Zn level × source interaction (quadratic, P = 0.007) was observed in liver Zn concentrations. This resulted from liver Zn concentrations plateauing at 150 mg Zn/kg when ZnO was supplemented, while there was a linear increase when using ZnAA. Increasing Zn in diets containing RAC increased (linear, P < 0.05) plasma Zn on d 18 and 32. The expression of IL-1ß was increased (P = 0.014) in mucosa of pigs fed the RAC diet compared with those fed the control diet. Expression of IL-1ß decreased (linear, P = 0.026) in the mucosa of pigs fed increasing added Zn. In conclusion, adding Zn to diets containing RAC resulted in a trend for improved growth performance of pigs in 1 of 2 experiments. Also, additional Zn increased plasma Zn and reduced IL-1ß.

Effects of dietary vitamin E concentration and source on sow, milk, and pig concentrations of α-tocopherol.

A total of 126 gilts and sows (PIC 1050) and their litters were used to determine the effects of dietary vitamin E concentration and source on sow plasma, milk, and pig concentrations of α-tocopherol. Additionally, we estimated the bioavailability of D-α-tocopheryl acetate (D-α-TAc) relative to DL-α-tocopheryl acetate (DL-α-TAc) when fed in diets containing dried distillers grains with solubles (DDGS). The 6 dietary treatments included DL-α-TAc at 44 and 66 mg/kg and D-α-TAc at 11, 22, 33, and 44 mg/kg. From breeding to d 69 of gestation, sows were fed 2.0 kg/d of a diet containing 40% DDGS, 0.30 mg/kg added Se, and no added vitamin E. Vitamin E treatments were fed from d 70 of gestation through weaning. Plasma was collected from sows on d 69 and 100 of gestation, at farrowing, and at weaning. Colostrum and milk samples were also collected. Plasma from 3 pigs per litter and heart and liver samples from 1 pig per litter were collected at weaning. Plasma, milk, and tissues from 6 litters per treatment were analyzed for α-tocopherol. Although tissue, plasma, and milk concentrations of α-tocopherol were the primary response criteria of interest, sow and litter performance were measured. As expected, treatment effects were not observed for lactation feed intake, sow BW, or backfat measurements. A trend (P = 0.085) for a treatment effect on average pig BW at weaning was detected, with pigs nursing sows fed 44 mg/kg DL-α-TAc weighing less because of a younger weaning age. No other differences in litter performance were observed. As D-α-TAc increased in the diet, sow plasma, colostrum, and milk, pig plasma, and pig heart concentrations of α-tocopherol increased (linear, P < 0.03). Sows fed diets with 44 mg/kg D-α-TAc had increased (P < 0.03) plasma and colostrum and pig plasma concentrations of α-tocopherol compared with sows fed 44 mg/kg of DL-α-TAc. Sows fed 66 mg/kg DL-α-TAc also had greater (P = 0.022) plasma α-tocopherol at weaning than sows fed 44 mg/kg DL-α-TAc. Bioavailability coefficients for D-α-TAc relative to DL-α-TAc ranged from 1.9 to 4.2 for sow and pig plasma α-tocopherol, 2.9 to 3.6 for colostrum α-tocopherol, 1.6 for milk α-tocopherol, and 1.7 to 2.0 for pig heart and liver α-tocopherol. Overall, this study indicates the bioavailability for D-α-TAc relative to DL-α-TAc varies depending on the response criteria but is greater than the standard potency value of 1.36.

The effects of feeder design and dietary dried distillers' grains with solubles on the performance and carcass characteristics of finishing pigs.

Three experiments were conducted to compare the effects of a conventional dry (five 30.5-cm spaces 152.4 cm wide; Staco Inc., Schaefferstown, PA) vs. a wet-dry (double sided; each side = 38.1-cm space; Crystal Spring; GroMaster Inc., Omaha, NE) finishing feeder (Exp. 1 and 2) and to evaluate the effects of feeder design and dietary level of dried distillers' grains with solubles (DDGS; >10% oil; Exp. 3) on performance and carcass characteristics of finishing pigs. In Exp. 1, 1,186 pigs (32.1 kg BW) were used in a 69-d experiment. There were 26 to 28 pigs per pen and 22 pens per feeder design, and all pigs received the same diets in 4 phases. In Exp. 2, 1,236 pigs (28.7 kg BW) were used in a 104-d experiment, with 25 to 28 pigs per pen and 23 pens per feeder design, and all pigs received the same diets in 5 phases. Carcass measurements were obtained from 11 pens of each feeder design after harvest. In Exp. 3, 1,080 pigs (35.1 kg BW) were used in a 99-d 2 × 2 factorial with main effects of feeder design (dry vs. wet-dry feeders) and DDGS (20 vs. 60%) with 10 pens of 27 pigs per treatment and all diets fed in 4 phases. Jowl fat samples were collected from 2 pigs per pen for fatty acid analysis and iodine value (IV) determination. In all experiments, pigs fed with the wet-dry feeder had greater (P < 0.05) ADG, ADFI, and final BW. In Exp. 2 and 3, HCW and backfat depth were increased (P < 0.05) for pigs fed with a wet-dry feeder, but G:F and fat-free lean index (FFLI) were reduced. Jowl IV was also reduced (P < 0.05) with a wet-dry feeder in Exp. 3. Pigs fed 60% DDGS in Exp. 3 had decreased (P < 0.05) ADG, G:F, final BW, HCW, and backfat but increased jowl IV and a tendency (P < 0.07) toward greater FFLI regardless of feeder type. In conclusion, pigs fed with this specific type of wet-dry feeder had improved ADG and ADFI, poorer G:F, and increased backfat depth compared to pigs fed with a conventional dry feeder. The poorer growth performance and increased jowl IV of pigs fed diets with 60% DDGS was similarly exhibited for pigs fed on both feeders.

The effects of sodium sulfate in the water of nursery pigs and the efficacy of nonnutritive feed additives to mitigate those effects.

Two experiments were conducted to investigate the effects of sodium sulfate water and the efficacy of nonnutritive feed additives in nursery pig diets. In Exp. 1, 320 barrows (5.4 ± 0.1 kg BW and 21 d of age) were allotted to 1 of 8 treatments for 24 d in a 2 × 4 factorial with 2 levels of sodium sulfate water (control or 3,000 mg sodium sulfate/L added), and 4 dietary zeolite (clinoptilolite) levels (0, 0.25, 0.50, or 1%). Fecal samples were collected on d 5, 9, 16, and 23; visually scored for consistency (1 = firm and 5 = watery); and analyzed for DM. No interactions of sodium sulfate × zeolite were observed for any response criteria. Overall (d 0 to 24), pigs drinking sodium sulfate water had decreased (P < 0.01) ADG, ADFI, and G:F compared with pigs drinking control water. Pigs drinking sodium sulfate water also had increased (P < 0.01) fecal scores and lower (P < 0.04) fecal DM on d 5, 9, and 16 compared with pigs drinking control water. Increasing dietary zeolite increased (linear; P < 0.05) ADG and ADFI but had no effect on G:F. In Exp. 2, 350 barrows (5.7 ± 0.1 kg BW and 21 d of age) were allotted to 1 of 10 treatments in a 2 × 5 factorial for 21 d with 2 levels of sodium sulfate water (control or 2,000 mg sodium sulfate/L added) and 5 dietary treatments (control, 1 or 2% zeolite, 1% humic acid substance [HA], and 1% humic and fulvic acid substance [HFB]). Fecal samples were collected on d 5, 8, 15, and 21; visually scored for consistency (1 = firm and 5 = watery); and analyzed for DM. Overall (d 0 to 21), a water source × diet interaction was observed for ADG and G:F because pigs fed the 1% HA had decreased (P < 0.01) ADG and G:F when drinking sodium sulfate water compared with other treatments but increased ADG and G:F when drinking control water. Pigs drinking sodium sulfate water had decreased (P < 0.01) ADG and G:F and tended (P < 0.08) to have decreased ADFI compared with pigs drinking control water. Pigs drinking sodium sulfate water had increased (P < 0.01) fecal scores and decreased (P < 0.01) fecal DM on d 5 and 8. In conclusion, water high in sodium sulfate concentrations decreased growth performance and increased fecal moisture in newly weaned pigs. Although zeolite improved growth performance in the first experiment, it did not influence growth in the second study. The nonnutritive feed additives used in both experiments were unsuccessful in ameliorating the increased osmotic diarrhea observed from high sodium sulfate water.

Effects of preslaughter feed withdrawal time on finishing pig carcass, body weight gain, and food safety characteristics in a commercial environment.

The effects of feed withdrawal time before slaughter on finishing pig carcass composition were evaluated in 2 studies. In Exp. 1, 728 pigs (BW = 128.9 ± 1.2 kg) were allotted to 1 of 4 treatments in a randomized design with number of pigs per pen and location within barn balanced across treatment. The 4 treatments were feed withdrawal times of 8, 24, 36, or 48 h and there were 12 replicate pens per treatment. Before feed withdrawal, pigs were fed a standard corn-soybean meal diet containing dried distillers grains with solubles (DDGS), bakery coproducts, and 5.0 mg/kg ractopamine HCl. Feed withdrawal time decreased (linear; P < 0.02) live weight, HCW, and backfat while increasing percentage yield (quadratic; P < 0.01) and fat-free lean index (FFLI; linear; P < 0.001). In Exp. 2, 843 pigs (BW = 125.4 ± 1.6 kg) were used to determine the impact of feed withdrawal on growth, carcass, blood lactate, and meat quality. There were 4 treatments: withholding feed for 8, 12, 24, or 36 h, with 10 replicates per treatment. Pigs were fed a common corn-soybean meal-based diet containing 20% DDGS and 5.0 mg/kg ractopamine HCl. Withholding feed decreased (linear; P < 0.001) live weight, ultimately resulting in decreased (P < 0.01) HCW. There were no differences in FFLI or backfat, but percentage yield (linear; P < 0.001) increased with longer withdrawal times. Carcass contaminations by stomach contents escaping from the oral cavity after shackling (leaking ingesta) or visible fecal contamination of the exterior of the carcass (runny bung) were also measured. Although withholding feed did not affect runny bung, it increased (linear; P < 0.001) the incidence of leaking ingesta, whereas blood lactate, visual color score, and purge loss were unaffected. Withholding feed increased 45-min pH (quadratic; P > 0.02) and ultimate pH (linear; P < 0.01) and increased (quadratic; P < 0.03) visual marbling score. Withholding feed decreased (linear; P < 0.001) feed intake, resulting in feed savings of up to 3 kg/pig. Although several heavyweight pigs were removed before trial commencement and the variable number of remaining pigs per pen may have influenced the response to feed withdrawal, the present data indicates that finishing pigs can experience between 24 and 36 h of feed withdrawal without negatively affecting carcass composition. However, the increased incidence of leaking ingesta beyond 12 h of feed withdrawal is concerning.

Effects of chlortetracycline and copper supplementation on antimicrobial resistance of fecal Escherichia coli from weaned pigs.

Feed-grade chlortetracycline (CTC) and copper are both widely utilized in U.S. pig production. Cluster randomized experiment was conducted to evaluate the effects of CTC and copper supplementation in weaned pigs on antimicrobial resistance (AMR) among fecal Escherichia coli. Four treatment groups: control, copper, CTC, or copper plus CTC were randomly allocated to 32 pens with five pigs per pen. Fecal samples were collected weekly from three pigs per pen for six weeks. Two E. coli isolates per fecal sample were tested for phenotypic and genotypic resistance against antibiotics and copper. Data were analyzed with multilevel mixed effects logistic regression, multivariate probit analysis and discrete time survival analysis. CTC-supplementation was significantly (99% [95% CI=98-100%]) associated with increased tetracycline resistance compared to the control group (95% [95% CI=94-97%]). Copper supplementation was associated with decreased resistance to most of the antibiotics tested, including cephalosporins, over the treatment period. Overall, 91% of the E. coli isolates were multidrug resistant (MDR) (resistant to ≥3 antimicrobial classes). tetA and blaCMY-2 genes were positively associated (P<0.05) with MDR categorization, while tetB and pcoD were negatively associated with MDR. tetA and blaCMY-2 were positively associated with each other and in turn, these were negatively associated with both tetB and pcoD genes; which were also positively associated with one another. Copper minimum inhibitory concentration was not affected by copper supplementation or by pcoD gene carriage. CTC supplementation was significantly associated with increased susceptibilities of E. coli to copper (HR=7 [95% CI=2.5-19.5]) during treatment period. In conclusion, E. coli isolates from the nursery pigs exhibited high levels of antibiotic resistance, with diverse multi-resistant phenotypic profiles. The roles of copper supplementation in pig production, and pco-mediated copper resistance among E. coli in particular, need to be further explored since a strong negative association of pco with both tetA and blaCMY-2 points to opportunities for selecting a more innocuous resistance profile.

The effects of porcine intestinal mucosa protein sources on nursery pig growth performance.

Three studies were conducted to compare the effects of 4 different porcine intestinal mucosa products (PEP2, PEP2+, Peptone 50, and PEP-NS; TechMix Inc., Stewart, MN) with select menhaden fish meal (SMFM) on nursery pig performance. These intestine-derived mucosal ingredients are byproducts of heparin production, with a similar amount of mucosal protein, but differ based on the carriers with which they are co-dried. Enzymatically processed vegetable protein is the carrier for PEP2 whereas PEP2+ is co-dried with enzymatically processed vegetable proteins and biomass from crystalline AA production. Peptone 50 uses vegetable protein as its carrier while PEP-NS is co-dried with byproducts of corn wet milling and biomass from crystalline AA production. In Exp. 1, 300 weanling pigs (PIC 327 × 1050; initially 5.4 kg and 19 d of age) were allotted to 1 of 5 dietary treatments with 12 replications and 5 pigs per pen. Diets consisted of a negative control (NC) containing no specialty protein sources, NC with 4, 8, or 12% PEP2 in phases 1 (d 0 to 11) and 2 (d 11 to 25), and a positive control containing 4% spray-dried animal plasma (SDAP) in phase 1 and 4% SMFM in phase 2. From d 0 to 11, pigs fed SDAP had greater (P < 0.05) ADG and G:F than pigs fed PEP2. From d 11 to 25, increasing PEP2 increased (quadratic; P < 0.01) ADG and G:F, with the greatest response observed at 4%. In Exp. 2, 960 weanling pigs (Newsham GPK35 × PIC 380; initially 5.6 kg, and 20 d of age) were allotted to 1 of 5 dietary treatments with 32 pigs per pen and 6 replications per treatment. Diets included a control with 4.5% SDAP in phase 1 (d 0 to 7) and no specialty protein sources in phase 2 (d 7 to 21) or the control diet with 6% of the following: SMFM, PEP2+, Peptone 50, or PEP-NS. From d 0 to 21, pigs fed diets containing SMFM, PEP2+, or PEP-NS had greater (P < 0.05) ADG than pigs fed the control or 6% Peptone 50. In Exp. 3, 180 nursery pigs (PIC 327 × 1050; initially 6.4 kg and 28 d of age) were allotted to 1 of 5 dietary treatments with 5 pigs per pen and 6 replications per treatment. Treatment diets were fed from d 7 to 21 postweaning. Treatments consisted of a NC, NC with 3, 6, 9, or 12% PEP-NS, or NC with 6% SMFM. Overall, pigs fed increasing PEP-NS had improved (quadratic; P < 0.01) ADG and G:F, with the greatest improvement observed in pigs fed 6% PEP-NS, similar to those fed 6% SMFM. These results suggest PEP2, PEP2+, and PEP-NS can effectively replace SMFM in nursery pig diets.

Effect of dietary zinc and ractopamine hydrochloride on pork chop muscle fiber type distribution, tenderness, and color characteristics.

A total of 320 finishing pigs (PIC 327 × 1050; initially 98 kg) were used to determine the effects of adding Zn to diets containing ractopamine HCl (RAC) on muscle fiber type distribution, fresh chop color, and cooked meat characteristics. Dietary treatments were fed for approximately 35 d and consisted of a corn-soybean meal-based negative control (CON), a positive control diet with 10 mg/kg of RAC (RAC+), and the RAC+ diet plus 75, 150, or 225 mg/kg added Zn from either ZnO or Availa-Zn. Loins randomly selected from each treatment (n = 20) were evaluated using contrasts: CON vs. RAC+, interaction of Zn level × source, Zn level linear and quadratic polynomials, and Zn source. There were no Zn source effects or Zn source × level interactions throughout the study (P > 0.10). Pigs fed RAC+ had increased (P < 0.02) percentage type IIX and a tendency for increased (P = 0.10) percent type IIB muscle fibers. Increasing added Zn decreased (linear, P = 0.01) percentage type IIA and tended to increase (P = 0.09) IIX muscle fibers. On d 1, 2, 3, 4, and 5 of display, pork chops from pigs fed the RAC+ treatment had greater (P < 0.03) L* values compared to the CON. On d 0 and 3 of display, increasing added Zn tended to decrease (quadratic, P = 0.10) L* values and decreased (quadratic, P < 0.03) L* values on d 1, 2, 4, and 5. Pigs fed RAC+ had decreased (P < 0.05) a* values on d 1 and 4 of display and tended to have decreased (P < 0.10) a* values on d 0 and 2 compared to CON pork chops. Pork chops from the RAC+ treatment had a tendency for increased (P < 0.08) oxymyoglobin percentage compared to CON pork chops on d 1, 2, 4, and 5. On d 0, as dietary Zn increased in RAC+ diets, there was a decrease (linear, P < 0.01) in the formation of pork chop surface oxymyoglobin percentage. Metmyoglobin reducing ability (MRA) of pork chops on d 5 was decreased in the RAC+ group. Chops from pigs fed added Zn had increased (quadratic, P < 0.03) MRA on d 3 and 5 of the display period. There was a trend for increased (linear, P = 0.07) cooking loss with increasing Zn in RAC diets and treatments did not affect tenderness as measured by Warner-Bratzler shear force (P > 0.07). In conclusion, RAC+ diets produced chops that were lighter and less red but maintained a greater percentage of surface oxymyoglobin throughout a 5-d simulated retail display. Ractopamine reduced MRA at the end of the display period, but supplementing Zn to RAC diets restored MRA to near CON treatment levels at the end of the display period.

The effects of immunological castration and corn dried distillers grains with solubles withdrawal on growth performance, carcass characteristics, fatty acid analysis, and iodine value of pork fat depots.

A total of 1,360 pigs were used in a 125-d study to determine the effects of corn dried distillers grains with solubles (DDGS) withdrawal after immunological castration (Improvest, Zoetis, Kalamazoo, MI) on growth performance and carcass fat quality of pigs. Pens of male pigs (initially 24 kg) were randomly allotted by BW and castration method (physically castrated [PC] or immunologically castrated [IC] barrows) to 1 of 3 diets with 8 replications per treatment and 27 to 29 pigs per pen. Treatments were arranged in a 2 × 3 factorial with main effects of castration method and diet (0% DDGS throughout, 30% DDGS throughout, or 30% DDGS through d 75 then no DDGS to d 125). Intact males were injected with Improvest on d 39 and 74 (IC). No castration method × diet interactions (P > 0.12) were observed for growth performance. Before the second Improvest injection (d 0 to 74), PC barrows had increased (P < 0.05) ADFI but were less efficient (P < 0.05) than intact males. After the second Improvest injection until the first marketing event (d 74 to 107), IC barrows had improved (P < 0.05) ADG and G:F compared with PC barrows. From d 0 to 107, IC barrows had improved (P < 0.05) ADG, G:F, and lower ADFI than PC barrows. The inclusion of 30% DDGS decreased (P < 0.05) G:F compared with pigs fed the control diet. For the period after the second Improvest injection (d 74 to 125), IC barrows had increased (P < 0.05) ADG, ADFI, and G:F compared with PC barrows. Overall (d 0 to 125), IC barrows had improved (P < 0.05) ADG and G:F and lower ADFI than PC barrows. The inclusion of 30% DDGS decreased (P < 0.05) G:F. Carcass yield was lower (P < 0.05) for IC than PC barrows. Pigs fed 30% DDGS throughout had decreased (P < 0.05) carcass yield; however, withdrawing DDGS from the diet on d 74 was effective at fully recovering the yield loss. Carcass fat iodine values (IV) were consistently higher (P < 0.05), regardless of fat depot or harvest time when 30% DDGS were included in the diet. Multiple 2-way interactions (P < 0.05) were detected between castration method, DDGS, depot, and time. Interactions were a result of fatty acid profiles changing more rapidly in backfat and belly fat than in jowl fat from d 107 to 125 and more dramatically in IC than PC barrows in the same period. This improvement from d 107 to 125 could be caused by the dilution of unsaturated fatty acids, specifically C18:2 and C18:3, due to rapid deposition of fat from de novo synthesis in IC barrows.

Nutrient database for sorghum distillers dried grains with solubles from ethanol plants in the Western Plains Region and their effects on nursery pig performance.

Samples of sorghum distillers dried grains with solubles (DDGS) were collected and analyzed to establish a nutrient database and evaluate the quality and consistency between and within 5 ethanol plants in Kansas and Texas. Each sample (n = 21) was analyzed for AA, DM, CP, crude fiber, crude fat, ash, NDF, ADF, trace minerals, and starch. Mean values (DM basis) were 0.88% Lys, 10.49% crude fat, 34.21% CP, and 4,722 kcal/kg GE. The standard deviations among sorghum DDGS plants were similar to those within plants for most nutrients. Results of these analyses were used to formulate diets for 2 nursery trials. The 2 experiments were conducted to determine the effects of adding sorghum DDGS (29.0% CP and 7.2% crude fat) to corn- or sorghum-based diets on nursery pig growth performance. In Exp. 1, 360 nursery barrows (6.8 kg and 26 d of age) were used in a 34-d study. Pigs were allotted to 1 of 8 dietary treatments with 5 pigs per pen and 9 pens per treatment. Treatments were arranged in a 2 × 4 factorial with main effects of grain source (corn vs. sorghum) and sorghum DDGS (0, 15, 30, or 45%). Diets were formulated to 1.30 and 1.25% standardized ileal digestible (SID) Lys in phases 1 and 2, respectively, but were not balanced for energy. Overall, there were no differences among pigs fed sorghum- or corn-based diets for ADG and ADFI; however, as sorghum DDGS increased from 0 to 45% of the diet, ADG decreased (linear, P < 0.01). There was a DDGS × grain source interaction (linear, P < 0.04) observed for G:F. In corn-based diets, pigs fed increasing sorghum DDGS had relatively similar G:F. However, in pigs fed sorghum-based diets, G:F was best for those fed 0% DDGS but was decreased in pigs fed 15, 30, or 45% sorghum DDGS. In Exp. 2, 180 nursery pigs (10.7 kg and 38 d of age) were used in a 21-d study with 6 pigs per pen and 5 pens per treatment. Treatments were arranged in a 2 × 3 factorial with main effects of grain source (corn vs. sorghum) and DDGS (0 vs. 30% corn or sorghum DDGS). Diets were formulated to 1.27% SID Lys and were not balanced for energy. Overall, there were no differences in ADG among pigs fed sorghum- or corn-based diets as well as no differences among pigs fed sorghum or corn DDGS. Pigs fed diets with 30% DDGS gained less (P < 0.03) than pigs fed basal diets. These results indicate sorghum can be a suitable replacement for corn in nursery pig diets, but increasing sorghum DDGS decreased ADG.

Effects of supplemental vitamin D3 on serum 25-hydroxycholecalciferol and growth of preweaning and nursery pigs.

Four experiments were conducted to investigate the effects of varying concentrations of supplemental vitamin D3 on pig growth, feed preference, serum 25-hydroxycholecalciferol [25(OH)D3] , and bone mineralization of nursing and weanling pigs. In Exp. 1, 270 pigs (1.71 ± 0.01 kg BW) were administered 1 of 3 oral vitamin D3 dosages (none, 40,000, or 80,000 IU vitamin D3) on d 1 or 2 of age. Increasing oral vitamin D3 increased serum 25(OH)D3 on d 10 and 20 (quadratic, P < 0.01) and d 30 (linear, P < 0.01). No differences were observed in ADG before weaning or for nursery ADG, ADFI, or G:F. Vitamin D3 concentration had no effect on bone ash concentration or bone histological traits evaluated on d 19 or 35. In Exp. 2, 398 barrows (initially 7 d of age) were used in a 2 × 2 split plot design to determine the influence of vitamin D3 before (none or 40,000 IU vitamin D3 in an oral dose) or after weaning (1,378 or 13,780 IU vitamin D3/kg in nursery diets from d 21 to 31 of age) in a 45-d trial. Before weaning (7 to 21 d of age), oral vitamin D3 dose did not influence growth but increased (P < 0.01) serum 25(OH)D3 at weaning (d 21) and tended (P = 0.08) to increase 25(OH)D3 on d 31. Increasing dietary vitamin D3 concentration from d 21 to 31 increased (P < 0.01) serum 25(OH)D3 on d 31. Neither the oral vitamin D3 dose nor nursery vitamin D3 supplements influenced nursery ADG, ADFI, or G:F. In Exp. 3, 864 pigs (initially 21 d of age) were allotted to 1 of 2 water solubilized vitamin D3 treatments (none or 16,516 IU/L vitamin D3 provided in the drinking water from d 0 to 10) in a 30-d study. Providing vitamin D3 increased serum 25(OH)D3 concentrations on d 10, 20, and 30; however, vitamin D3 supplementation did not affect overall (d 0 to 30) ADG, ADFI, or G:F. In Exp. 4, 72 pigs were used in a feed preference study consisting of 2 feed preference comparisons. Pigs did not differentiate diets containing either 1,378 or 13,780 IU vitamin D3/kg but consumed less (P < 0.01) of a diet containing 44,100 IU vitamin D3/kg compared with the diet containing 1,378 IU vitamin D3/kg. Overall, these studies demonstrate that supplementing vitamin D3 above basal concentrations used in these studies is effective at increasing circulating 25(OH)D3, but the supplement did not influence growth or bone mineralization. Also, concentrations of vitamin D3 of 44,100 IU/kg of the diet may negatively affect feed preference of nursery pigs.

Effects of lowering dietary fiber before marketing on finishing pig growth performance, carcass characteristics, carcass fat quality, and intestinal weights.

A total of 264 pigs (initially 41.0 kg BW) were used in a 90-d study to determine the effects of lowering dietary fiber before market on pigs fed high dietary fiber [provided by wheat middlings (midds) and distillers dried grains with solubles (DDGS)] on growth performance, carcass characteristics, carcass fat quality, and intestinal weights of growing-finishing pigs. Pens of pigs were randomly allotted by initial BW and sex to 1 of 6 treatments with 6 replications per treatment and 7 or 8 pigs per pen. A positive control (corn-soybean meal-based) diet containing no DDGS or midds (9.3% NDF) and a negative control diet with 30% DDGS and 19% midds (19% NDF) were fed throughout the entire trial (d 0 to 90). The other 4 treatments were arranged in a 2 × 2 factorial with the main effects of length of fiber reduction (23 or 47 d before marketing) and fiber level fed during the reduction period (low or medium). Pigs on these treatments were fed the negative control before the reduction treatment. The medium-fiber diet contained 15% DDGS and 9.5% midds (14.2% NDF) with the low-fiber diet was the positive control diet. Increasing the feeding duration of the low-fiber diets lowered overall ADFI (linear, P = 0.03) and improved G:F (linear, P < 0.01). Lowering the fiber level for the last 23 d did not influence growth performance; however, lowering the fiber level improved carcass yield (P = 0.002), with a greater response (P < 0.001) when the low-fiber diet was fed for 23 d. Jowl fat iodine value (IV) decreased when the longer lower fiber diets were fed (linear, P < 0.01) and was lower (P < 0.001) for pigs fed the low-fiber diet during the fiber reduction period than pigs fed the medium-fiber diet during the same time period; however, increasing the time lower fiber diets were fed from 23 to 47 d further reduced (P < 0.01) jowl IV. Increasing the duration that the control diet was fed by increasing the reduction time from 23 to 47 d increased (P < 0.01) backfat depth. Reducing the fiber level decreased full large intestine weight (linear, P = 0.005) with a greater response (P = 0.04) when the low-fiber diet was fed during the reduction period instead of the medium-fiber diet. In summary, lowering the fiber level before marketing can improve G:F, carcass yield, carcass IV, and reduce large intestine weight; however, the optimal duration of the fiber reduction period depends on the targeted response criteria.

An evaluation of the effects of added vitamin D3 in maternal diets on sow and pig performance.

A total of 84 sows (PIC 1050) and their litters were used to determine the effects of supplementing maternal diet with vitamin D3 on sow and pig performance, serum 25-hydroxyvitamin D3 (25(OH)D3), milk vitamin D3, neonatal bone mineralization, and neonatal tissue vitamin D3. After breeding, sows were randomly assigned to 1 of 3 dietary vitamin D3 treatments (1,500, 3,000, or 6,000 IU/kg of complete diets). Sows were bled on d 0 and 100 of gestation and at farrowing and weaning (d 21). Pig BW was recorded at birth and weaning, and serum was collected from 2 pigs/litter at birth, on d 10 and at weaning. A total of 54 pigs (18/treatment) were euthanized at birth and necropsied to sample bones and tissues. Sow and suckling pig performance and neonatal bone ash and bone density did not differ among maternal vitamin D3 treatments; however, sow 25(OH)D3 and milk vitamin D3 increased (linear, P < 0.01) with increasing maternal vitamin D3 supplementation. Piglet serum 25(OH)D3 increased (quadratic, P < 0.03) with increased maternal vitamin D3. Neonatal kidney vitamin D3 tended (quadratic, P = 0.08) to decrease with increasing maternal vitamin D3, but liver vitamin D3 tended (linear, P = 0.09) to increase with increasing maternal vitamin D3. At weaning, a subsample of 180 pigs (PIC 327 × 1050) were used in a 3 × 2 split plot design for 35 d to determine the effects of maternal vitamin D3 and 2 levels of dietary vitamin D3 (1,800 or 18,000 IU/kg) from d 0 to 10 postweaning on nursery growth and serum 25(OH)D3. Overall (d 0 to 35), nursery ADG and G:F were not affected by either concentration of vitamin D3, but ADFI tended (quadratic, P < 0.06) to decrease with increasing maternal vitamin D3 as pigs from sows fed 3,000 IU had lower ADFI compared with pigs from sows fed 1,500 or 6,000 IU/kg. Nursery pig serum 25(OH)D3 increased with increasing maternal vitamin D3 (weaning) on d 0 (linear, P < 0.01), and maternal × diet interactions (P < 0.01) were observed on d 10 and 21 because pigs from sows fed 1,500 IU had greater increases in serum 25(OH)D3 when fed 18,000 IU compared with pigs from sows fed 3,000 IU. In conclusion, sow and pig serum 25(OH)D3, milk vitamin D3, and neonatal tissue vitamin D3 can be increased by increasing maternal vitamin D3, and nursery pig 25(OH)D3 can be increased by increasing dietary vitamin D3; however, sow and pig performance and neonatal bone mineralization was not influenced by increasing vitamin D3 dietary levels.

Effects of dietary L-carnitine and ractopamine HCl on the metabolic response to handling in finishing pigs.

Two experiments (384 pigs; C22 × L326; PIC) were conducted to determine the interactive effect of dietary L-carnitine and ractopamine HCl (RAC) on the metabolic response of pigs to handling. Experiments were arranged as split-split plots with handling as the main plot and diets as subplots (4 pens per treatment). Dietary L-carnitine (0 or 50 mg/kg) was fed from 36.0 kg to the end of the experiments (118 kg), and RAC (0 or 20 mg/kg) was fed the last 4 wk of each experiment. At the end of each experiment, 4 pigs per pen were assigned to 1 of 2 handling treatments. Gently handled pigs were moved at a moderate walking pace 3 times through a 50-m course and up and down a 15° loading ramp. Aggressively handled pigs were moved as fast as possible 3 times through the same course, but up and down a 30° ramp, and shocked 3 times with an electrical prod. Blood was collected immediately before and after handling in Exp. 1 and immediately after and 1 h after handling in Exp. 2. Feeding RAC increased (P < 0.01) ADG and G:F, but there was no effect (P > 0.10) of L-carnitine on growth performance. In Exp. 1 and 2, aggressive handling increased (P < 0.01) blood lactate dehydrogenase (LDH), lactate, cortisol, and rectal temperature and decreased blood pH. In Exp. 1, there was a RAC × handling interaction (P < 0.06) for the difference in pre- and posthandling blood pH and rectal temperature. Aggressively handled pigs fed RAC had decreased blood pH and increased rectal temperature compared with gently handled pigs, demonstrating the validity of the handling model. Pigs fed RAC had increased (P < 0.01) LDH compared with pigs not fed RAC. Pigs fed L-carnitine had increased (P < 0.03) lactate compared with pigs not fed L-carnitine. In Exp. 2, pigs fed RAC had lower (P < 0.02) blood pH immediately after handling, but pH returned to control levels by 1 h posthandling. Lactate, LDH, cortisol, and rectal temperature changes from immediately posthandling to 1 h posthandling were not different (P > 0.10) between pigs fed L-carnitine and those fed RAC, indicating that L-carnitine did not decrease recovery time of pigs subjected to aggressive handling. These results suggest that pigs fed 20 mg/kg of RAC are more susceptible to stress when handled aggressively compared with pigs not fed RAC. Dietary L-carnitine fed in combination with RAC did not alleviate the effects of stress. This research emphasizes the importance of using proper animal handling techniques when marketing finishing pigs fed RAC.

The effects of diet form and feeder design on the growth performance of finishing pigs.

Two studies were conducted to determine the effects of diet form (meal vs. pellet) and feeder design (conventional dry vs. wet/dry) on finisher pig performance. Experiments were arranged as 2 × 2 factorials with 11 replications per treatment and 26 to 29 pigs per pen. In Exp. 1, pigs (n = 1,290; initial BW 46.8 kg) were used in a 91-d study. Pelleted diets averaged approximately 35% fines throughout the study. Overall, pigs fed pelleted diets or via wet/dry feeders had greater (P < 0.07 and 0.001, respectively) ADG than pigs fed meal diets or fed with a dry feeder. Diet form × feeder interactions (P < 0.02) were observed for G:F. Pigs fed either meal or pelleted diets via a wet/dry feeder had similar G:F, but pigs fed pelleted diets in dry feeders had poorer G:F than pigs with meal diets in dry feeders. In Exp. 2, pigs (n = 1,146; initial BW 38.2 kg) were used in a 104-d study. From d 0 to 28, a diet form × feeder design interaction (P < 0.01) was observed for ADG, which was due to decreased ADG in pigs fed pelleted diets from a conventional dry feeder compared with pigs fed meal diets from the same feeder type whereas there was no difference in wet/dry feeders based on diet form. Pigs fed pelleted diets had poorer (P < 0.01) G:F than pigs fed meal diets. This result appeared to be due to poor pellet quality (39.6% fines). From d 42 to 86, pellet quality improved (4.4% fines) and a diet form × feeder interaction was observed for ADG in which pigs fed meal diets in a dry feeder had decreased (P < 0.05) ADG than pigs fed pelleted diets in dry feeders or pigs presented either diet in wet/dry feeders. Pigs fed pelleted diets had improved (P < 0.001) G:F. Pigs fed via wet/dry feeders had increased (P < 0.03) ADFI and G:F compared with pigs fed via dry feeders. Overall, pigs fed with wet/dry feeders had increased (P < 0.02) ADG and ADFI and poorer G:F than pigs with dry feeders whereas pigs given pelleted diets had improved (P = 0.05) G:F compared with pigs presented meal diets. These studies found that pigs fed from wet/dry feeders had increased ADG and ADFI compared with pigs fed via dry feeders regardless of diet form. Additionally, pellet quality appeared to influence responses because pigs fed high-quality pellets via dry feeders had better growth performance than pigs fed meal diets. Conversely, if pellet quality was poor, the feed efficiency benefits associated with pelleting were lost.

Effects of standardized ileal digestible tryptophan:lysine in diets containing 30% dried distillers grains with solubles on finishing pig performance and carcass traits.

Two experiments were conducted to determine the effects of standardized ileal digestible (SID) Trp:Lys in grow-finish swine diets containing 30% dried distillers grains with solubles (DDGS). Within each experiment, crystalline Lys and Trp replaced soybean meal to alter the dietary SID Trp:Lys concentration but maintain minimum ratios of other AA to Lys. In Exp. 1, 638 pigs (36.3 kg initial BW) were used in a 105-d trial (6 pens per treatment). Pens of pigs were randomly allotted to 1 of 4 dietary treatments with SID Trp:Lys of 14.0, 15.0, 16.5, and 18.0%. From d 0 to 42, as Trp:Lys increased, ADG increased (quadratic; P = 0.05) and ADFI tended to increase (quadratic; P = 0.07) with no changes in G:F. Both ADG and ADFI were maximized at Trp:Lys of 16.5%. From d 42 to 105, increasing SID Trp:Lys increased (linear; P < 0.001) ADG and ADFI. Unlike data from d 0 to 42, the response was linear through the greatest SID Trp:Lys of 18.0%. Overall (d 0 to 105), increasing SID Trp:Lys increased (linear; P < 0.001) final BW, ADG, ADFI, and HCW. In Exp. 2, 1,214 pigs (66.3 kg initial BW) were used in a 73-d finishing trial (9 pens per treatment). Pens of pigs were randomly allotted to 1 of 5 dietary treatments with SID Trp:Lys of 15.0, 16.5, 18.0, and 19.5 and the 15.0% Trp:Lys diet with l-Trp added to achieve 18.0% SID Trp:Lys. Overall (d 0 to 73), ADG, ADFI, G:F, and final BW improved (linear; P < 0.03) as dietary SID Trp:Lys increased through 19.5%. No differences were found in growth performance between the 2 diets containing 18.0% SID Trp:Lys. For carcass traits, increasing SID Trp:Lys resulted in increased HCW (linear; P = 0.01) and a tendency toward a decreased (quadratic; P = 0.09) backfat depth and fat-free lean index (FFLI), with pigs fed diets containing 16.5 and 18.0% SID Trp:Lys having increased FFLI and lower backfat depth compared with pigs fed 15.0 and 19.5% SID Trp:Lys. Pigs fed the diet with added crystalline Trp tended to have increased (P = 0.08) backfat depth and decreased FFLI (P = 0.10) compared with pigs fed the same SID Trp:Lys without crystalline Trp. The results indicated that the optimal SID Trp:Lys was 16.5% from 36.3 to 72.6 kg but at least 19.5% from 72.6 to 120.2 kg in corn-soybean meal diets containing 30% DDGS.