Purdue University 2002 Swine Research Report

Effects of Ractopamine and Carnitine in Diets Containing 5% Fat for Finishing Pigs

S. A. Trapp1, B. T. Richert1, A. P. Schinckel1, and K. Q. Owen2
1Department of Animal Sciences, Purdue University and 2Lonza, Inc., Fair Lawn, NJ.

Introduction

The activation The pork industry is continually looking for means to increase pig growth rate, feed efficiency, and carcass lean percentage. To accomplish this, one option would be to explore increasing the amount of energy available for lean gain accretion. It is known that energy intake limits pig performance from 25 - 120 lb live weight. Therefore, by increasing dietary fat levels, energy intake and pig growth rate could be increased. However, the efficiency in which dietary fat is utilized for lean growth may decrease as dietary fat levels increase and as the pig matures. To compensate for this problem, it has been found that feeding carnitine may improve the utilization efficiency of dietary fat.

Recently ractopamine (RAC) has been approved as a feed additive to increase lean growth rate, improve feed efficiency, and increase carcass lean percentage. Based on research conducted at Purdue University, the duration of response to ractopamine has decreased to four weeks. With a four-week duration response, it is important to maximize daily energy intakes to maximize the total response to ractopamine. As a result, it is thought that elevated fat diets with the inclusion of carnitine may enhance the lean accretion of pigs fed ractopamine by effectively increasing the available energy for lean tissue synthesis.

The objective of this study is to incorporate ractopamine and carnitine into diets with elevated fat levels to determine the effects on growth rate, feed efficiency, and lean gain of finishing pigs.

Materials and Methods

Three hundred gilts (avg. initial BW = 188.3 lb) of two genetic populations, one high lean gain lower feed intake European terminal cross (ET) and one medium lean gain U.S. terminal cross (UST), were randomly assigned one of five diets fed for four weeks before slaughter. Six pens were assigned to each treatment/genotype combination (60 pens on test). Five dietary treatments (TRT) were used: 1) the control (CONT); 2) 45 g/ton carnitine (CARN); 3) 4.5 g/ton RAC (RAC4.5); 4) 45 g/ton carnitine and 4.5 g/ton RAC (CARN+RAC); and 5) 9 g/ton RAC (RAC9). Table 1 displays the diet formulations for each treatment of the trial. Two weeks prior to starting the dietary treatments, all gilts were fed a 1.15% lysine corn-soy diet with no added fat. Treatment diets were formulated to 1.15% lysine and contained 5% added choice white grease. The gilts and feeders were weighed to determine average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (F:G) on days 0, 14, and 28. In addition, 3 gilts/pen (36/TRT) were ultrasonically scanned on days 0, 14, and 28 to measure loin eye area, and last rib and tenth rib backfat. With these real-time ultrasound data, tissue accretion curves were generated. After four weeks on test, the gilts were taken to a commercial pork processor where individual hot carcass weights and carcass ultrasounds of loin and backfat depth measurements were collected. Pork quality measurements of the loin (color, marbling, firmness, and pH) were additionally evaluated at the time of slaughter for a subset of gilts. An average of two independent, objective pork quality scores was recorded. Statistical analysis of all the data was performed using the GLM procedures of SAS, allowing dietary treatment to be examined for its effect on growth and carcass characteristics of the finishing pigs.

Results

Diet effects. The growth performance data of the finishing pigs can be found in Tables 2 and 3. While initial and final body weight of the gilts proved to be statistically insignificant, the gilts that were fed diets with ractopamine had numerically heavier body weights by day 28. Pigs fed the CARN+RAC and the RAC9 diets had greater ADG during days 0-14 (1.84, 1.91, 2.10, 2.32, 2.37 lb/d; P < 0.001, diets 1-5 respectively) and overall from days 0-28 (1.88, 1.86, 2.00, 2.12, 2.08 lb/d; P < 0.01, diets 1-5 respectively) compared to pigs fed the CONT and CARN diets. No significant difference was found in ADFI among diets at any time point in the study. Gilts fed the RAC4.5, CARN+RAC, and RAC9 diets had greater feed efficiency (P < 0.001) from days 0-14 (0.37, 0.38, 0.43, 0.45, 0.47 G:F, diets 1-5 respectively) and days 0-28 (0.36, 0.35, 0.39, 0.40, 0.40 G:F, diets 1-5 respectively) compared to pigs fed the CONT and CARN diets.

The results of the plant-measured carcass characteristics are shown in Tables 4 and 5. Hot carcass weights (183.6, 182.1, 186.3, 188.7, 189.4 lb, diets 1-5 respectively) for gilts fed the CARN+RAC and RAC9 diets were found to be greater (P < 0.05) than those fed the CONT and CARN diets. Pigs fed diets with ractopamine also had increased carcass loin depths (2.67, 2.65, 2.78, 2.77, 2.83 in; P < 0.01, diets 1-5 respectively). However, only the RAC4.5 and RAC9 diets had increases in percent lean (P < 0.01) compared to the other diets. No difference in percent carcass yield was found among treatments. The pigs fed RAC9 resulted in a significant increase (P < 0.01) in carcass grade premium (6.95 $/cwt.) compared to those fed the CONT or CARN diets (5.98 and 6.11 $/cwt) while the RAC4.5 and CARN+RAC diets resulted in intermediate grade premiums (6.49 and 6.47 $/cwt.). As a result, the CARN+RAC and RAC9 diets produced a significantly higher (P < 0.01) total value per pig than the CONT and CARN diets ($121.93, $121.53, $125.12, $126.80, $128.08, diets 1-5 respectively).

Pork quality measurements were also evaluated and the results are presented in Tables 4 and 5 as well. Marbling and firmness did not differ significantly among treatments, but the CARN+RAC diet resulted in a darker color score (2.09, 2.06, 2.04, 2.34, 1.99; P < 0.05, diets 1-5 respectively) than the other treatments.

The results of the real-time ultrasound data can be found in Tables 6 and 7. Table 6 provides data for serial scans of a subset of pigs from each pen at days 0, 14, and 28. By day 28 pigs fed diets with ractopamine but no carnitine resulted in a significant decrease in last rib backfat (0.58, 0.58, 0.52, 0.58, 0.53 in; P < 0.05, diets 1-5 respectively). Pigs fed the CARN+RAC diet had an increase (P < 0.05) in loin eye area as compared to the CONT and CARN diets (6.96, 7.00, 7.22, 7.50, 7.33 in2; diets 1-5 respectively).

Genotype effects. The UST gilts had a greater ADG from day 14-28 (P < 0.006) and tended to have greater overall ADG from day 0-28 (2.03 vs. 1.95 lbs/day; P < 0.07) than the ET gilts. Since the ET gilts had lower ADFI (P < 0.02) during day 0-14, they had an improved feed efficiency during days 0-14 (P < 0.02) as well. However, because the UST gilts had a greater feed efficiency during days 14-28 (P < 0.06), there was no difference found between genotypes for feed efficiency during the entire trial, days 0-28.

At slaughter the UST gilts had greater final body weights (247.7 vs. 244.1 lbs; P < 0.03). However, the UST gilts also had increased fat depths (0.61 vs. 0.53 in; P < 0.001) with reduced percent lean (56.0 vs. 56.6%; P < 0.01) and reduced carcass yield (75.2 vs. 76.1%; P < 0.01) compared to the ET gilts. Similar to the plant-measured carcass data, the real-time ultrasound data indicated that the ET gilts had decreased backfat depth (0.58 vs. 0.66 in; P < 0.001) with no difference in LEA throughout the trial as compared to the UST gilts. The ET gilts also had less loin marbling characteristic (1.57 vs. 2.07; P < 0.001) than the UST gilts.

Application

This study indicates that during the first 14 days while feeding ractopamine, carnitine may enhance the ractopamine response with increased body weight gain and improved feed efficiency. Additionally, the combination of 45 g/ton carnitine and 4.5 g/ton ractopamine may provide the potential to increase gain and feed efficiency as well as provide similar carcass characteristics equal to the higher dose (9 g/ton) of ractopamine, resulting in a substantial savings in feed input costs when using ractopamine.

Table 1. Experimental diet compositions for finishing pigs

Diet Composition, %

Pre-Trial Diet

CONT

CARN

RAC4.5

CARN + RAC

RAC9

Corn

68.370

62.435

62.385

62.410

62.360

62.385

SBM - 48%

29.070

30.000

30.000

30.000

30.000

30.000

Limestone

1.000

0.960

0.960

0.960

0.960

0.960

Dical. Phos.

0.580

0.640

0.640

0.640

0.640

0.640

Salt

0.300

0.300

0.300

0.300

0.300

0.300

Vitamin Premix

0.250

0.250

0.250

0.250

0.250

0.250

TM Premix

0.125

0.125

0.125

0.125

0.125

0.125

Selenium Premix

0.050

0.050

0.050

0.050

0.050

0.050

Fat

0.000

5.000

5.000

5.000

5.000

5.000

Lysine - HCl

0.120

0.100

0.100

0.100

0.100

0.100

DL-Methionine

0.055

0.060

0.060

0.060

0.060

0.060

Phytase

0.080

0.080

0.080

0.080

0.080

0.080

Carnitine

0.000

0.000

0.050

0.000

0.050

0.000

Paylean-9

0.000

0.000

0.000

0.025

0.025

0.050

Totals

100.000

100.000

100.000

100.000

100.000

100.000


Nutrient Profile

Met. Energy, kcal/lb

1506.00

1593.00

1593.00

1593.00

1593.00

1593.00

Crude protein, %

19.530

19.500

19.500

19.500

19.500

19.500

Crude fiber, %

2.560

2.460

2.460

2.460

2.460

2.460

Crude fat, %

3.540

8.330

8.330

8.330

8.330

8.330


Amino Acids, %

Lysine

1.150

1.150

1.150

1.150

1.150

1.150

Threonine

0.736

0.736

0.736

0.736

0.736

0.736

Tryptophan

0.230

0.230

0.230

0.230

0.230

0.230

Methionine

0.365

0.370

0.370

0.370

0.370

0.370

Meth. + Cystine

0.710

0.710

0.710

0.710

0.710

0.710

Isoleucine

0.820

0.820

0.820

0.820

0.820

0.820


Minerals, %

Calcium

0.600

0.600

0.600

0.600

0.600

0.600

Total Phosphorous

0.500

0.500

0.500

0.500

0.500

0.500

Available Phosphorous

0.180

0.180

0.180

0.180

0.180

0.180

Phytase Avail. P

0.280

0.280

0.280

0.280

0.280

0.280

Potassium (K)

0.230

0.230

0.230

0.230

0.230

0.230

CONT = Control; CARN = 45 g/ton Carnitine; RAC4.5 = 4.5 g/ton Ractopamine; CARN+RAC = 45 g/ton Carnitine + 4.5 g/ton Ractopamine; RAC9 = 9 g/ton Ractopamine.

 

Table 2. The effect of varying levels of carnitine and/or ractopamine on ADG, ADFI, and feed efficiency in finishing pigs

 

Probability, P <

Treatment:

CONT

CARN

RAC4.5

CARN+ RAC

RAC9

SE

Diet

Genotype

Diet x Genotype

Initial wt., lb

188.5a

187.9a

188.2a

188.4a

188.6a

2.233

0.999

0.594

1.000

Day 14 wt., lb

215.2a

215.7a

218.7a

222.0a

223.0a

3.210

0.315

0.920

0.986

Day 28 wt., lb

241.8a

240.5a

244.9a

248.3a

247.5a

3.080

0.300

0.135

0.979


Day 0-14

ADG, lb/d

1.84c

1.91c

2.10cb

2.32ba

2.37a

0.095

0.004

0.616

0.762

ADFI, lb/d

4.89a

5.03a

4.90a

5.15a

5.09a

0.130

0.540

0.019

0.728

F:G

2.69a

2.67a

2.39b

2.24b

2.19b

0.096

0.004

0.032

0.546

G:F

0.37b

0.38b

0.43a

0.45a

0.47a

0.015

0.001

0.019

0.667


Day 14-28

ADG, lb/d

1.91a

1.80a

1.92a

1.89a

1.83a

0.079

0.784

0.006

0.767

ADFI, lb/d

5.67a

5.70a

5.40a

5.49a

5.37a

0.158

0.475

0.547

0.700

F:G

2.99ab

3.24a

2.87b

2.96ab

2.98ab

0.142

0.442

0.029

0.877

G:F

0.34a

0.32a

0.36a

0.35a

0.34a

0.016

0.496

0.058

0.928


Overall

ADG, lb/d

1.88b

1.86b

2.00ba

2.12a

2.08a

0.051

0.002

0.072

0.674

ADFI, lb/d

5.28a

5.36a

5.15a

5.32a

5.23a

0.133

0.809

0.128

0.690

F:G

2.80a

2.88a

2.59b

2.52b

2.52b

0.062

0.001

0.743

0.780

G:F

0.36b

0.35b

0.39a

0.40a

0.40a

0.008

0.001

0.940

0.838

a,b,c Means in a row with different superscripts differ, P < 0.05.
CONT = Control; CARN = 45 g/ton Carnitine; RAC4.5 = 4.5 g/ton Ractopamine; CARN+RAC = 45 g/ton Carnitine + 4.5 g/ton Ractopamine; RAC9 = 9 g/ton Ractopamine.

 

Table 3. Performance summary by genotype of finishing pigs fed varying levels of carnitine and ractopamine

 

Genotype

   
 

ET

UST

SE

Probability, P <

Initial wt., lb

187.8

188.8

1.412

 

Day 14 wt., lb

219.1

218.8

2.030

0.920

Day 28 wt., lb

242.5

246.7

1.948

0.135


Day 0-14

ADG, lb/d

2.13

2.09

0.060

0.616

ADFI, lb/d

4.87

5.15

0.082

0.019

F:G

2.34

2.53

0.061

0.032

G:F

0.44

0.40

0.009

0.019


Day 14-28

ADG, lb/d

1.77

1.97

0.050

0.006

ADFI, lb/d

5.48

5.57

0.100

0.547

F:G

3.15

2.86

0.091

0.029

G:F

0.33

0.35

0.010

0.058


Overall

ADG, lb/d

1.95

2.03

0.032

0.072

ADFI, lb/d

5.18

5.36

0.084

0.128

F:G

2.67

2.66

0.039

0.743

G:F

0.38

0.38

0.005

0.940

ET = European Terminal Cross gilts.
UST = U.S. Terminal Cross gilts.

 

Table 4. The effect of varying levels of carnitine and/or ractopamine on carcass characteristics in finishing pigs

 

Probability, P <

Treatment:

CONT

CARN

RAC4.5

CARN + RAC

RAC9

SE

Diet

Genotype

Diet x Genotype

Slaughter wt., lb

244.1b

241.6b

245.8ab

248.6a

249.5a

1.853

0.016

0.030

0.859

HCW, lb

183.6b

182.1b

186.3ab

188.7a

189.4a

1.530

0.002

0.638

0.765

Ave. fat depth, in

0.57abc

0.59ab

0.52c

0.62a

0.56bc

0.019

0.007

0.001

0.970

Ave. loin depth, in

2.67b

2.65b

2.78a

2.77a

2.83a

0.036

0.002

0.877

0.893

% Lean

56.02b

55.94b

56.81a

56.15b

56.76a

0.198

0.002

0.005

0.996

% Yield

75.21a

75.40a

75.80a

75.91a

75.94a

0.300

0.311

0.002

0.669

 

Base meat price, $/cwt.

60.42a

60.63a

60.63a

60.76a

60.74a

0.500

0.990

0.576

0.999

Carcass grade Premium, $/cwt.

5.98b

6.11b

6.49ab

6.47ab

6.95a

0.196

0.005

0.724

0.816

Total value, $/pig

121.93b

121.53b

125.12ab

126.80a

128.08a

1.313

0.001

0.875

0.910

 

Color1

2.09a

2.06a

2.04a

2.34b

1.99a

0.090

0.054

0.109

0.430

Marbling1

1.83a

1.92a

1.69a

1.92a

1.73a

0.093

0.293

0.001

0.999

Firmness1

2.34a

2.45a

2.33a

2.53a

2.35a

0.092

0.469

0.334

0.784

pH2

5.59b

5.64ab

5.61ab

5.70a

5.63ab

0.041

0.312

0.210

0.981

a,b,c Means in a row with different superscripts differ, P < 0.05.
1 n = 124.
2 n = 87.
CONT = Control; CARN = 45 g/ton Carnitine; RAC4.5 = 4.5 g/ton Ractopamine; CARN+RAC = 45 g/ton Carnitine + 4.5 g/ton Ractopamine; RAC9 = 9 g/ton Ractopamine.

 

Table 5. Genotypic carcass characteristics of finishing pigs fed varying levels of carnitine and ractopamine

 

Genotype

   
 

ET

UST

SE

Probability, P <

Slaughter wt., lb

244.1

247.7

1.172

0.030

HCW, lb

185.7

186.4

0.968

0.638

Ave. fat depth, in

0.53

0.61

0.012

0.001

Ave. loin depth, in

2.74

2.74

0.022

0.877

% Lean

56.59

56.08

0.126

0.005

% Yield

76.06

75.24

0.002

0.002

 

Base meat price, $/cwt.

60.76

60.51

0.317

0.576

Carcass grade Premium, $/cwt.

6.43

6.37

0.124

0.724

Total value, $/pig

124.79

124.60

0.830

0.875

 

Color1

2.17

2.04

0.055

0.121

Marbling1

1.57

2.07

0.058

0.001

Firmness1

2.36

2.44

0.057

0.347

pH2

5.61

5.66

0.026

0.190

1 n = 124.
2 n = 87.
ET = European Terminal Cross gilts.
UST = U.S. Terminal Cross gilts.

 

Table 6. The effect of varying levels of carnitine and/or ractopamine on back fat and loin eye area in finishing pigs

 

Probability, P <

Treatment:

CONT

CARN

RAC4.5

CARN+RAC

RAC9

SE

Diet

Genotype

Diet x Genotype

Serial scan, no. pigs

36

36

36

36

36

       


Day 0

Body wt., lb

187.3a

188.8a

189.4a

189.2a

188.6a

1.694

0.914

0.501

0.735

10th Rib BF, in

0.44a

0.48a

0.45a

0.48a

0.46a

0.014

0.207

0.001

0.313

Last Rib BF, in

0.50a

0.49a

0.51a

0.51a

0.47a

0.016

0.359

0.001

0.723

Loin Eye Area, in2

6.08a

6.20a

6.04a

6.02a

6.02a

0.126

0.844

0.451

0.695


Day 14

Body wt., lb

215.7b

216.3ab

218.8ab

222.7a

222.7a

2.348

0.088

0.964

0.637

10th Rib BF, in

0.52bc

0.57ab

0.50c

0.56ab

0.52bc

0.018

0.012

0.002

0.217

Last Rib BF, in

0.53a

0.52a

0.51a

0.53a

0.51a

0.013

0.810

0.001

0.111

Loin Eye Area, in2

6.79a

7.07a

7.00a

7.01a

7.20a

0.154

0.437

0.519

0.899


Day 28

Body wt., lb

241.3b

240.9b

246.1ab

248.7a

247.4a

2.259

0.044

0.082

0.945

10th Rib BF, in

0.62ab

0.65a

0.58b

0.66a

0.59b

0.020

0.018

0.001

0.464

Last Rib BF, in

0.58a

0.58a

0.52b

0.58a

0.53b

0.016

0.017

0.001

0.505

Loin Eye Area, in2

6.96b

7.00b

7.22ab

7.50a

7.33ab

0.140

0.037

0.947

0.911


Overall Change

10th Rib BF, in

0.18a

0.17ab

0.13b

0.19a

0.13b

0.016

0.027

0.820

0.962

Loin Eye Area, in2

0.88ab

0.80a

1.23bc

1.48c

1.35c

0.147

0.003

0.572

0.869

a,b,c Means in a row with different superscripts differ, P < 0.05.
CONT = Control; CARN = 45 g/ton Carnitine; RAC4.5 = 4.5 g/ton Ractopamine; CARN+RAC = 45 g/ton Carnitine + 4.5 g/ton Ractopamine; RAC9 = 9 g/ton Ractopamine.

 

Table 7. Genotypic differences in back fat and loin eye area of finishing pigs fed varying levels of carnitine and ractopamine

 

Genotype

   
 

ET

UST

SE

Probability, (P < )

Serial Scan, no. pigs

90

90

   


Day 0

Body wt., lb

188.2

189.2

1.071

0.501

10th Rib BF, in

0.42

0.50

0.009

0.001

Last Rib BF, in

0.46

0.53

0.010

0.001

Loin Eye Area, in2

6.12

6.03

0.080

0.451


Day 14

Body wt., lb

219.2

219.3

1.480

0.964

10th Rib BF, in

0.51

0.57

0.008

0.002

Last Rib BF, in

0.47

0.57

0.011

0.001

Loin Eye Area, in2

7.06

6.97

0.097

0.519


Day 28

Body wt., lb

243.1

246.7

1.433

0.082

10th Rib BF, in

0.58

0.66

0.010

0.001

Last Rib BF, in

0.53

0.59

0.013

0.001

Loin Eye Area, in2

7.20

7.21

0.089

0.947


Overall Change

10th Rib BF, in

0.16

0.16

0.010

0.820

Loin Eye Area, in2

1.11

1.18

0.092

0.572

ET = European Terminal Cross gilts.
UST = U.S. Terminal Cross gilts.


Index of 2002 Purdue Swine Research Articles