Effects of ractopamine hydrochloride on the growth performance and carcass characteristics of heavy-weight finishing pigs sent for slaughter using a 3-phase marketing strategy

Abstract A total of 2,158 crossbred pigs was used to evaluate the effects of feeding 7.4 mg/kg ractopamine hydrochloride (RAC) on the growth performance and carcass characteristics of heavy-weight finishing pigs sent to slaughter using a 3-phase marketing strategy. The study was performed from 121.0 ± 4.28 kg to 144.5 ± 4.73 BW using a randomized complete block design (blocking factor was d of start on test) with 2 treatments (0 vs. 7.4 mg/kg RAC). Pigs were housed in a commercial wean-to-finish facility in groups of approximately 25 (44 groups/treatment), with ad libitum access to feed and water throughout the study, and pen weights of pigs were recorded at the start (d 0), and on d 7, 21, and 35 of study. Pigs were sent for slaughter according to the following marketing strategy: 1) after 7 d on RAC, the heaviest 16% of each pen was sent for slaughter (Phase 1), 2) after 21 d on RAC, the next 40% of each pen was sent for slaughter (Phase 2), and 3) after 35 d on RAC, the remaining 44% of each pen was sent for slaughter (Phase 3). Pigs were selected for slaughter by visual appraisal and shipped to a commercial facility where standard carcass measurements (HCW, LM depth, and backfat depth) were measured. Overall, feeding RAC increased (P < 0.001) ADG (18.8%) and G:F (23.7%) compared to the control, but lowered (P < 0.001) ADFI (3.3%). In addition, feeding RAC increased (P < 0.001) HCW (3.9 kg), carcass yield (0.7% units), LM depth (5.0%), and predicted lean content (1.0% units), and reduced backfat depth (6.3% lower) compared to controls. With each subsequent phase of marketing, the magnitude of improvements in response to feeding RAC decreased for ADG (43.1, 20.9, and −3.1% for Phase 1, 2, and 3, respectively) and G:F (37.5, 25.8, and 6.4% for Phase 1, 2, and 3, respectively); however, improvements in HCW (1.6, 4.5, and 4.2 kg for Phase 1, 2, and 3, respectively), carcass yield (0.2, 0.6, and 0.9% units for Phase 1, 2, and 3, respectively), LM depth (2.3, 5.7, and 5.2% for Phase 1, 2, and 3, respectively), and predicted lean content (0.2, 1.0, and 1.3% units for Phase 1, 2, and 3, respectively) generally increased from feeding RAC. These results suggest that while improvements in growth performance from feeding RAC will generally decline after 21 d of feeding, improvements in carcass traits, particularly carcass yield and lean content, will continue with feeding RAC until d 35.

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Effect of narasin (Skycis) or zinc bacitracin (Albac) inclusion on the growth performance and carcass characteristics of finishing pigs sent for slaughter using a 3-phase marketing strategy

Translational Animal Science ◽

10.2527/tas2017.0058 ◽

2017 ◽

Vol 1 (4) ◽

pp. 518-525

Author(s):

J. W. Rickard ◽

G. L. Allee ◽

P. J. Rincker ◽

S. L. Gruber ◽

C. L. Puls ◽

...

Keyword(s):

Marketing Strategy ◽

Growth Performance ◽

Block Design ◽

Carcass Characteristics ◽

Dietary Treatment ◽

The Other ◽

Finishing Pigs ◽

Carcass Yield ◽

Zinc Bacitracin ◽

Dietary Treatments

Abstract The objective of this study was to evaluate the effect of dietary inclusion of narasin or zinc bacitracin on the growth performance and carcass characteristics of finishing pigs sent for slaughter using a 3-phase marketing strategy. The study used 2,219 crossbred pigs in a randomized complete block design (blocking factor = start date) with 3 dietary treatments: 1) Control (no feed additive), 2) 15 mg/kg narasin (Skycis, Elanco Animal Health, Greenfield, IN), and 3) 28 mg/kg zinc bacitracin (Albac, Zoetis, Parsippany, NJ). Pigs were housed in single-sex pens of 25 pigs in a commercial wean-to-finish facility and there were 30 pen-replicates of each dietary treatment. All pigs were weighed as a group (i.e., pen) on d 0 (start of experimental feeding period), 77, 91, and 105 (end) of study. Pigs had ad libitum access to feed and water throughout the study period; all feed additions to the feeder were recorded. Pigs were sent for slaughter according to the following marketing strategy: 1) after 77 d on study, the heaviest 20% of each pen was sent for slaughter (Phase 1), 2) after 91 d on study, the next heaviest 48% of each pen were sent for slaughter (Phase 2), and 3) after 105 d on study, the remaining 32% of each pen was sent for slaughter (Phase 3). Pigs within each pen were selected for slaughter by visual appraisal of weight and shipped to a commercial slaughter facility where standard carcass measurements (HCW, LM depth, and backfat depth) were measured. Feeding narasin increased (P < 0.05) final live BW (1.3 kg) and overall ADG (1.1%) compared to the other treatments, which were similar (P > 0.05). Dietary treatment did not impact (P > 0.05) overall G:F. Feeding narasin increased (P < 0.05) HCW (1.4 kg) and carcass yield (0.3% units) compared to the other dietary treatments, which were similar (P > 0.05) for these traits. Overall, these results demonstrate that narasin-fed pigs had improved overall growth rate, HCW, and carcass yield compared to controls or pigs fed zinc bacitracin.

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PSIV-15 Determining the effects of increasing levels of xylanase in nutrient adequate diets on growth performance, carcass characteristics of growing-finishing pigs

Journal of Animal Science ◽

10.1093/jas/skaa054.313 ◽

2020 ◽

Vol 98 (Supplement_3) ◽

pp. 176-177

Author(s):

Hayden R Kerkaert ◽

Joel M DeRouchey ◽

Steve S Dritz ◽

Robert D Goodband ◽

Mike D Tokach ◽

...

Keyword(s):

Growth Performance ◽

Block Design ◽

Average Daily Gain ◽

Carcass Characteristics ◽

Experimental Unit ◽

Finishing Pigs ◽

Carcass Yield ◽

Distillers Grains With Solubles ◽

Treatment Data ◽

Unit Body Weight

Abstract A total of 1,944 mixed sex growing-finishing pigs (PIC; 337×1050; initial BW of 22.5±0.53 kg) were used in a 131-d growth trial to determine the effects of increasing levels of xylanase in adequate diets on grow-finish pig growth performance and carcass characteristics. The 6 dietary treatments consisted of corn, soybean meal, and dried distillers grains with solubles with added xylanase (Belfeed B 1100 MP; Jefo Nutrition Inc., Saint-Hyacinthe, Quebec) formulated to: 0, 5, 10, 20, 40, and 75 of enzymatic activity for xylanase (IU/kg) with 27 pigs per pen and 12 replicates per treatment. Data were analyzed as a randomized complete block design using lmer function in lme4 package in R with pen considered as the experimental unit, body weight as blocking factor, and treatment as a fixed effect. From d 0 to 70, there was a tendency (quadratic, R=0.068) for average daily gain (ADG) to decrease and then increase with increasing added xylanase, but there was no evidence (R >0.10) of differences for average daily feed intake (ADFI) and feed efficiency (G/F). From d 70 to 131 and overall, there was no evidence of difference (R >0.10) observed for ADG, ADFI, and F/G. There was no evidence for difference (R >0.10) between treatments for number of pigs receiving injectable treatments or mortalities. For carcass traits, increasing xylanase increased then decreased (quadratic, R=0.010) percentage carcass yield. Also, as xylanase increased, percentage lean decreased (linear, R=0.038) and backfat marginally increased (linear, R=0.066). In conclusion, adding increasing levels of xylanase in nutrient adequate diets did not influence growth performance or mortality but did improve carcass yield when intermediate levels were fed.

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Effects of Substitution of Corn with Ground Brown Rice on Growth Performance, Nutrient Digestibility, and Gut Microbiota of Growing-Finishing Pigs

Animals ◽

10.3390/ani11020375 ◽

2021 ◽

Vol 11 (2) ◽

pp. 375

Author(s):

Sheena Kim ◽

Jin Ho Cho ◽

Younghoon Kim ◽

Hyeun Bum Kim ◽

Minho Song

Keyword(s):

Gut Microbiota ◽

Growth Performance ◽

Block Design ◽

Brown Rice ◽

Carcass Characteristics ◽

Basal Diet ◽

Nutrient Digestibility ◽

Growing Pigs ◽

Finishing Pigs ◽

Dietary Treatments

The present study was conducted to evaluate the effects of replacing corn with brown rice on growth performance, nutrient digestibility, carcass characteristics, and gut microbiota of growing and finishing pigs. A total of 100 growing pigs (23.80 ± 2.96 kg BW; 10 weeks of age) were randomly allotted to 4 dietary treatments (5 pigs/pen; 5 replicates/treatment) in a randomized complete block design (block = BW) as follows: corn-soybean meal basal diet (CON) and replacing corn with 50% (GBR50), 75% (GBR75), and 100% (GBR100) of ground brown rice. Each trial phase was for 6 weeks. During the growing period, there were no differences on growth performance and nutrient digestibility among dietary treatments. Similarly, no differences were found on growth performance, nutrient digestibility, and carcass characteristics of pigs during the finishing period among dietary treatments. As a result of the beta diversity analysis, microbial populations were not clustered between CON and GBR100 during the growing phase, but clustered into two distinct groups of CON and GBR100 during the finishing phase. In conclusion, brown rice can be added to the diets of growing-finishing pigs by replacing corn up to 100% without negatively affecting growth performance of the pigs; additionally, this may have an effect on changes in pig intestinal microbiota if continued for a long time.

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Bioavailability of l-lysine sulfate relative to l-lysine HCl for growing–finishing pigs

Translational Animal Science ◽

10.1093/tas/txz094 ◽

2019 ◽

Vol 3 (4) ◽

pp. 1254-1262 ◽

Cited By ~ 1

Author(s):

Qingyun Li ◽

Stacie A Gould ◽

John Khun Kyaw Htoo ◽

J Caroline González-Vega ◽

John F Patience

Keyword(s):

Growth Performance ◽

Phase 1 ◽

Carcass Characteristics ◽

Basal Diet ◽

Growing Pigs ◽

Ratio Method ◽

Experimental Unit ◽

Finishing Pigs ◽

Phase 3 ◽

Commercial Diet

Abstract The objective of this study was to evaluate the relative bioavailability (RBV) of l-Lys sulfate in comparison to l-Lys HCl based on the growth performance response from approximately 26 to 48 kg and from approximately 68 to 114 kg. The effect of Lys source on blood urea nitrogen (BUN), digestibility of dry matter (DM) and sulfur (S), as well as carcass characteristics was determined. A total of 280 growing pigs (25.9 ± 0.25 kg BW) were randomly assigned to one of seven dietary treatments in 56 pens, with five pigs per pen. The diets included a Lys-deficient basal diet (65% of requirement) and the basal diet supplemented with three graded levels of Lys (75%, 85%, and 95% of requirement), as either l-Lys HCl (78.8% Lys purity) or l-Lys sulfate (54.6% Lys purity). The experiment lasted for 112 d, with four dietary phases: Phase 1 lasted for 4 wk (BW: 25.9 to 47.5 kg), Phase 2 lasted for 3 wk (common commercial diet as washout period), Phase 3 lasted for 5 wk (BW: 67.5 to 98.2 kg), and Phase 4 lasted for 3 or 4 wk to reach an average market weight of 114.2 kg. Fresh fecal samples of pigs fed the highest levels of Lys (both Lys sources) were collected on 7 to 10 days after the beginning of Phase 3 for digestibility assay. Blood samples were collected on day 21 and day 81 to determine BUN. Carcass data were collected at a commercial packing plant. Data were analyzed using PROC GLM of SAS (9.4) according to a completely randomized design with pen as the experimental unit. The RBV of l-Lys sulfate was determined using the multiple regression slope-ratio method. Increasing levels of Lys, independent of source, increased (P < 0.05) BW, ADG, and feed efficiency during Phases 1, 3, and 4; market BW increased linearly (P < 0.01) and backfat and BUN decreased linearly (P < 0.01). Lysine source had no impact on growth performance, carcass characteristics, BUN, or digestibility of S and DM. The RBV of l-Lys sulfate compared with l-Lys HCl was also not different based upon ADG or G:F during Phase 1, 3, or 4. These data suggest that the bioavailability of Lys in l-Lys sulfate and l-Lys HCl is at least equivalent for growing–finishing pigs.

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Effects of two feeding periods of tiamulin fed in combination with chlortetracycline for control and treatment of swine respiratory and enteric disease and subsequent growth performance of growing-finishing pigs

Translational Animal Science ◽

10.1093/tas/txy097 ◽

2018 ◽

Vol 3 (1) ◽

pp. 113-122

Author(s):

Christopher L Puls ◽

James M Hammer ◽

Kevin Eggers ◽

Amanda Graham ◽

Brandon Knopf ◽

...

Keyword(s):

Growth Performance ◽

Block Design ◽

Individual Therapy ◽

Finishing Pigs ◽

Enteric Disease ◽

Subsequent Growth ◽

Carcass Yield ◽

Single Sex ◽

The Difference ◽

Dietary Treatments

Abstract The objective of this study was to evaluate the effects of two dietary feeding periods of tiamulin in combination with chlortetracycline for the control and treatment of swine respiratory and enteric disease and subsequent growth performance. The study used 1,151 commercial crossbred barrows and gilts in a randomized complete block design. Pigs were housed in single-sex groups of 25 at a floor space of 0.69 m2/pig. There were two dietary treatments: 1) nonmedicated controls and 2) 39 mg/kg tiamulin + 441 mg/kg chlortetracycline (TIACTC) fed from days 7 to 20 and again days 49 to 62. There were 23 pens per treatment group. Daily observations were made throughout the study, including the number of pigs in each pen coughing, with diarrhea, or showing signs of lameness as well as the number of pigs in each pen requiring individual therapy treatment for each symptom. Pigs were weighed as a group on days 0 (for allocation purposes), 7, 21, 49, 61, 89 (start of marketing), and at time of slaughter. Within pen, animals were selected by visual appraisal and sent for slaughter over 4 wk to a commercial slaughter facility where HCW was collected and used to calculate carcass yield. There was no difference (P > 0.05) between treatments for the incidence of morbidity or mortality. Pigs fed TIACTC tended to have less coughing observations (P = 0.10) and less diarrhea observations (P = 0.08) during the study period, and had less observations of lameness (P < 0.001) and required less treatments than nonmedicated controls (P < 0.001). For the overall study period, pigs fed TIACTC had greater (P < 0.05) total BW gain (43.3 kg greater/pen) and greater (P < 0.05) ADG and ADFI than controls. There was no effect (P > 0.05) of treatment on G:F. Overall, pigs fed TIACTC weighed 1.3 kg heavier (P < 0.05) at the start of marketing and completed the study with an overall BW advantage of 1.6 kg (P < 0.05) compared to controls. The difference between treatments for live BW increased with marketing group (1.0 kg in marketing group 1 and 3.3 kg in marketing group 4). Pigs fed TIACTC had greater (P < 0.05) HCW (1.0 kg) than controls; however, there was no difference (P > 0.05) between treatments for carcass yield. The results of this study suggest that feeding TIACTC was successful at controlling respiratory and enteric disease and, consequently, improved growth performance and carcass weight of grow-finish pigs.

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PSIX-10 Effects of SID Lysine:Calorie NE ratio on the Growth Performance and Carcass Characteristics of DNA 600 Sired Pigs

Journal of Animal Science ◽

10.1093/jas/skaa054.320 ◽

2020 ◽

Vol 98 (Supplement_3) ◽

pp. 181-181

Author(s):

Brittany Carrender ◽

Hayden E Williams ◽

Mandy Gerhart ◽

Kyle Coble ◽

Joel M DeRouchey ◽

...

Keyword(s):

Growth Performance ◽

Removal Rate ◽

Block Design ◽

Carcass Characteristics ◽

Experimental Unit ◽

Carcass Quality ◽

Carcass Yield ◽

Randomized Complete Block Design ◽

Dietary Treatments

Abstract A total of 2,673 mixed sex pigs (DNA 600 × PIC 1050; initially 21.4 kg BW) were used in a 117-d study to evaluate the effects of increasing SID Lysine:Calorie NE ratio on the growth performance and carcass characteristics of DNA sired pigs. Pens of pigs (30 pigs/pen) were blocked by BW and location and allotted to 1 of 4 dietary treatments with 18 pens per treatment. Treatments were 90%, 95%, 100%, or 105% of the 2016 PIC recommended SID Lysine:Calorie NE ratio for finishing gilts. Data were analyzed as a randomized complete-block design with pen as the experimental unit. Overall (d 0-117), increasing Lysine:Calorie NE tended to improve ADG (Linear; P = 0.077) and G:F (Linear; P = 0.053). Although there was an increase in ADG with increasing SID Lysine:Calorie NE, there was no evidence for a difference (P > 0.100) in final BW. The lack of BW response is most likely due to the lower (Quadratic; P < 0.008) removal rate as SID Lysine:Calorie NE increased. Carcass ADG (Linear; P < 0.064) tended to improve as SID Lysine: Calorie NE increased. An improvement in carcass G:F (Quadratic; P < 0.004) was observed as SID Lysine:Calorie NE increased to 100% PIC (2016) recommendations, with little improvement observed thereafter. No significant differences were observed in carcass yield, loin depth, back fat, or % lean. These results suggests that DNA sired pigs fed increasing SID Lysine:Calorie NE ratios tended to have improved growth performance with no impact on carcass quality.

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Effects of narasin or virginiamycin on growth performance and carcass characteristics of growing and finishing pigs

Translational Animal Science ◽

10.1093/tas/txab020 ◽

2021 ◽

Author(s):

Sara K Linneen ◽

Roger A Arentson ◽

J Jeffrey Chewning ◽

Scott N Carr

Keyword(s):

Growth Performance ◽

Block Design ◽

Animal Health ◽

Carcass Characteristics ◽

Experimental Unit ◽

Finishing Pigs ◽

Incomplete Block Design ◽

Finishing Pig ◽

Effect Of Treatment ◽

Main Effects

Abstract The objective of this experiment was to determine the effects of narasin (NAR; Skycis®; Elanco Animal Health, Greenfield, IN) or virginiamycin (VIR; Stafac®; Phibro Animal Health Corporation, Teaneck, NJ) on finishing pig growth performance and carcass characteristics. Two separate experiments were conducted at the same site in 2013 and 2014. A total of 576 pigs (initial BW = 23.2 ± 0.19 kg) were housed in 24 pens with 8 pigs per pen in Exp. 1. In Exp. 2, a total of 888 pigs (initial BW = 26.2 ± 0.12 kg) were housed in 39 pens with 8 pigs per pen. Treatments consisted of a series of unmedicated corn-soybean meal diets (CON), CON + NAR (15 mg/kg), or CON + VIR (11 mg/kg) fed for 108 d (Exp. 1) or 109 d (Exp. 2). Pen was the experimental unit in both studies. Data were analyzed as a randomized complete block design with the main effects of block and treatment (Exp. 1) and as an incomplete block design with the fixed effect of treatment and the random effects of barn and barn within block (Exp. 2). In Exp.1, NAR and VIR increased (P < 0.05) ADG and ADFI from d 0 to 28, and BW on d 28, 56, 76 and 97 as compared to pigs fed CON. During day 0 to 28, pigs fed NAR had a greater (P < 0.05) G:F than those fed CON or VIR. Also, during d 28 to 56 pigs fed VIR had a greater (P < 0.05) ADFI than pigs fed CON. Pigs fed NAR or VIR had greater (P < 0.05) carcass yield than those fed CON. In Exp.2, feeding NAR increased (P < 0.05) pig BW from d 54 through 96 compared to pigs fed CON or VIR. No differences (P > 0.05) in ADG were detected between pigs fed VIR and CON through the first 74 d, but ADG of pigs fed VIR was similar to (P > 0.05) those fed NAR from d 26 to 54. From do 0 to 109, NAR improved ADG compared to pigs fed VIR, which also had similar gain to those consuming CON (P = 0.04). Feed efficiency was similar between pigs fed NAR and VIR with pigs fed CON intermediate (P = 0.05). Pigs fed NAR had a greater (P < 0.05) HCW and loin depth than those fed CON or VIR. A subtherapeutic dose of VIR showed improvements in growth performance that were similar to NAR in one experiment. Although there were differences in the magnitude of growth and carcass effects of NAR between the two studies, pigs fed NAR showed at least a tendency to have greater G:F and in some cases increased carcass weight and yield compared to pigs consuming nonmedicated feed.

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123 Growth performance and nutrient digestibility of multi-enzyme-supplemented low-energy and -amino acid diets for growing and finishing pigs

Journal of Animal Science ◽

10.1093/jas/skz122.128 ◽

2019 ◽

Vol 97 (Supplement_2) ◽

pp. 69-70

Author(s):

Kevin S Jerez Bogota ◽

Christian Sanchez ◽

Jimena Ibagon ◽

Maamer Jlali ◽

Pierre Cozannet ◽

...

Keyword(s):

Growth Performance ◽

Block Design ◽

Phase 1 ◽

Positive Control ◽

Negative Control ◽

Nutrient Digestibility ◽

Growing Pigs ◽

Finishing Pigs ◽

P Content ◽

Randomized Complete Block Design

Abstract Objective was to determine the effects of supplementing corn-soybean meal-based diets with a multi-enzyme on growth performance and apparent total tract digestibility (ATTD) of nutrients in growing pigs. A total of 276 pigs (BW = 33.99 ± 4.3 kg) were housed by sex in 45 pens of 6 or 7 pigs and fed 5 diets (9 pens/diet) in a randomized complete block design. Diets were positive control (PC); and negative control 1 (NC1) or negative control 2 (NC2) without or with multi-enzyme. The multi-enzyme used supplied at least 1,250, 860, 4,600, and 1,000 units of xylanase, β-glucanase, arabinofuranosidase and phytase per kilogram of diet, respectively. The PC was adequate in all nutrients according to NRC (2012) recommendations and had greater digestible P content than NC1 diet or NC2 diet by 0.134 percentage points. The NC1 diet had lower NE and digestible AA content than PC diet by 3%. The NC2 diet had lower NE and digestible AA content than PC diet by 5%. The diets were fed in 4 phases based on BW; Phase 1: 34–50 kg, Phase 2: 50–75 kg, Phase 3: 75–100 kg, and Phase 4: 100–120 kg. Nutrient digestibility was determined at the end of Phase 1. Overall (34–120 kg BW), pigs fed the PC and NC1 diets did not differ in ADG and ADFI. Pigs fed NC2 diet had lower (PPPP > 0.10). Supplemental multi-enzyme increased (P = 0.047) the ATTD of GE for NC2 diet. In conclusion, the NE and digestible AA and P can be lowered by ≤ 5% in multi-enzyme-supplemented diets without effects on growth performance pigs.

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137 Evaluation of Narasin Inclusion Level on the Growth Performance and Carcass Characteristics of Growing-finishing Pigs

Journal of Animal Science ◽

10.1093/jas/skab054.113 ◽

2021 ◽

Vol 99 (Supplement_1) ◽

pp. 69-70

Author(s):

Christopher L Puls ◽

Roger Arentson ◽

Beau A Peterson ◽

Gustavo Silva ◽

Brandon Knopf ◽

...

Keyword(s):

Growth Performance ◽

Block Design ◽

Carcass Characteristics ◽

Fixed Time ◽

Carcass Weight ◽

Finishing Pigs ◽

Final Body Weight ◽

Randomized Complete Block Design ◽

Inclusion Level ◽

Ad Libitum

Abstract Two studies were conducted to evaluate narasin inclusion level on the growth performance and carcass characteristics of growing-finishing pigs. The studies were carried out using a randomized complete block design with three narasin levels: 0 vs. 15 vs. 20 mg/kg. Study 1 (2,232 pigs) was carried out over a fixed time of 85 days from 33.4 ± 1.7 kg to 117.0 ± 2.6 kg. Study 2 (1,125 pigs) was carried out over a fixed time of 113 days from 28.0 ± 2.2 kg to 124.4 ± 6.0 kg. All pigs were fed diets that met or exceeded nutrient recommendations of growing-finishing pigs (NRC, 2012). Pigs were offered ad libitum access to feed and water throughout the study and weighed on day 0, 28, 56, and 84. Feed additions and feed remaining in the feeder at the time of pig weighing was recorded. Due to disruptions at the slaughter facility, carcass data were not collected on Study 1. For Study 2, pigs were sent for slaughter over five weeks, with the heaviest 20% of each pen being sent for slaughter each week. At slaughter, hot carcass weight was collected. Compared to controls, feeding 15 mg/kg narasin increased (P < 0.05) final body weight (1.2 kg and 1.4 kg for Study 1 and 2, respectively), increased (P < 0.05) hot carcass weight (1.3 kg), and tended (P = 0.07) to improve carcass yield (0.3 percentage units). Feeding 20 mg/kg narasin increased (P < 0.05) overall G:F compared to controls (1.5% and 1.9% for Study 1 and 2, respectively). There were limited differences between the 15 and 20 mg/kg narasin levels. The results of this study confirm improvements in growth performance and carcass characteristics from feeding narasin to growing-finishing pigs. The outcomes of feeding 20 mg/kg narasin were unexpected and warrant further research.

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