Purdue University 2001 Swine Research Report

Evaluation of the Effects of Dietary Fat, Conjugated Linoleic Acid, and Ractopamine on Growth Performance and Carcass Quality in Genetically Lean Gilts

T. E. Weber, K. Enright, B. T. Richert, and A. P. Schinckel
Department of Animal Sciences, Purdue University

Introduction

The pork industry is constantly seeking economical methods which will increase production efficiency and carcass quality. Three nutritional management “tools” at pork producer’s disposal that have been demonstrated to improve growth performance and carcass characteristics are: 1) adding rendered animal fats to diets; 2) adding the recently approved feed additive ractopamine to finishing diets; and 3) adding conjugated linoleic acid (CLA) to diets. Adding animal fats to diets has long been known to enhance the feed efficiency of finishing swine (Seerly et al., 1978; Stahly et al., 1979). Supplementing swine diets with CLA has been shown to improve feed efficiency and enhance carcass quality by increasing lean percentage and belly firmness (Dugan et al., 1997; Schinckel et al., 2000). Ractopamine, when added to finishing swine diets, increases growth performance, carcass lean, and carcass yield (Herr et al., 2000). However, limited research has been conducted as to the interactions and combined effects of dietary fat, CLA, and ractopamine.

Furthermore, the goal of this experiment was to determine the individual and combined effects of dietary fat, CLA, and ractopamine on the growth performance and carcass quality of a genetically lean population of gilts.

Materials and Methods

Gilts (n = 180; Newsham XL sires x Newsham parent females; initial BW = 130 lb) were assigned to a 2 x 2 x 3 factorial arrangement consisting of dietary CLA, ractopamine, and fat treatments. The CLA treatment consisted of a 1% commercially available CLA product containing 60% CLA isomers (.6% CLA) or 1% soybean oil (Table 1). Ractopamine levels were either 0 or 9 g/ton. Dietary fat treatments consisted of: 1) diets containing 0% added fat;
2) diets containing 5% choice white grease (CWG); or 3) diets containing 5% beef tallow (BT). The CLA and dietary fat treatments were initiated at 130 lb BW, 4 weeks prior to the ractopamine treatments. The ractopamine treatments were imposed when the gilts reached an average body weight of 188 lb and lasted for the duration of final 4 weeks until carcass data were collected.

The gilts and feeders were weighed every two weeks to monitor growth performance and feed intake. At the completion of the 4 wk trial when the gilts averaged 247 lb body weight, carcass data were collected at the Purdue University abattoir. Carcass data collected included: carcass weight, 45 minute and 24 hour loin pH, last rib midline backfat depth, 10^th rib inner and outer layer backfat thickness, and 10^th rib loin eye area. Subjective loin color, marbling, and firmness measurements were taken at the interface of the 10^th and 11^th rib (NPPC, 1999). In addition, objective loin color (L*, a*, and b*) and water holding capacity were determined. At 24 hours postmortem, belly firmness measurements were recorded by placing the bellies skin side down centered horizontally over a metal bar. Firmness was analyzed as the length measured between the anterior and posterior end of the belly when it was suspended over the bar. Therefore, firmer bellies result in greater values of the length measured between the anterior and posterior ends when suspended over a bar. Additionally, subjective firmness scores (range 1 to 5) were assigned to the bellies with a score of 5 being assigned to the firmest and a score of 1 being assigned to the softest bellies.

Results

The growth performance data for the duration of the ractopamine treatment (wk 4 to 8) are summarized in Tables 2 and 3. Gilts fed diets containing ractopamine had greater (P <0.01) daily gains and converted feed more efficiently (P < .01) than gilts fed diets devoid of ractopamine. Gilts fed CLA containing diets had greater (P < .03) ADG and were more (P < .01) feed efficient during wk 6 to 8 than gilts not fed CLA. For the last 4 wks of the trial, gilts fed CLA demonstrated greater (P < .02) feed efficiency than gilts consuming the 1% soybean oil diets. Adding 5% fat to the diet as either CWG or BT decreased (P < .02) feed intake during wk 6 to 8 and wk 4 to 8 while concurrently improving (P < .01) feed efficiency during the same time periods. For the overall experimental period (wk 0 to 8) gilts fed 9 g/ton ractopamine had greater (P < .01) daily gains and feed efficiencies than gilts fed 0 g/ton ractopamine (Tables 4 and 5). Feeding diets containing .6% CLA increased (P < .01) feed efficiency, but had no effect (P > .10) upon daily gain nor feed intake. Fat, provided as either CWG or BT, tended (P < .10) to increase average daily gain, decreased (P < .02) feed intake, and improve (P < .01) feed efficiency compared to gilts fed diets containing 0% added fat. Final body weights were increased (P < .01) by feeding 9 g/ton ractopamine and tended (P < .10) to be increased by adding 5% fat to the diets. Gilts fed CLA tended (P < .07) to have greater ADG during wk 6 to 8 while also being fed ractopamine compared to gilts fed SBO and ractopamine.

The carcass characteristics data are presented in Tables 6 and 7. Feeding diets containing 9g/ton ractopamine increased (P < .01) both carcass weight and dressing percentage. It was also found that adding 5% fat as either CWG or BT to the diets increased (P < .01) carcass weight and tended (P < .06) to increase dressing percentage. Predicted lean percentage was increased by 1.6% (57.8 vs 56.2 %; P < .01) by feeding ractopamine. An increase (P < .03) in predicted lean percentage was also found in gilts fed diets containing .6% added CLA versus gilts fed 1% soybean oil. Outer layer 10^th rib backfat depth was decreased (P < .01) and total 10^th rib backfat tended (P < .10) to decrease in gilts fed either the 9g/ton ractopamine or .6% CLA treatments as compared to gilts fed diets devoid of ractopamine or CLA. Adding 5% fat as either CWG or BT to the diet tended (P < .09) to increase the outer layer backfat depth. Within the fat treatments, gilts fed diets containing CWG had increased (P < .05) 10^th rib inner layer, 10^th rib total , and last rib fat depths and tended (P < .07) to have greater 10^th rib outer layer backfat depth versus gilts fed diets containing BT. Both the CLA and fat treatments affected last rib fat depth. Gilts fed diets containing CLA had less (P < .01) and gilts fed diets containing fat as either CWG or BT, had increased (P < .01) last rib fat depth as compared to gilts fed diets without CLA or 5% added fat, respectively. Gilts fed diets containing ractopamine or 5% added fat had greater (P < .01) loin eye areas than gilts fed diets devoid of ractopamine or fat. Loin eye area tended (P < .06) to be increased in gilts fed CLA as compared to gilts fed diets containing no added CLA.

The data representing the quality characteristics of longissimus dorsi and bellies are presented in Tables 8 and 9. Both the CLA and added fat treatments tended (P < .10) to affect subjective marbling scores as gilts fed either CLA or added fat had numerically greater marbling scores than gilts fed diets devoid of CLA or fat. Gilts fed diets containing ractopamine tended (P < .07) to have lower subjective belly firmness than gilts fed diets containing no ractopamine. However, this difference was not supported by the objective belly firmness measurements as there was no difference (P > .10) between gilts fed ractopamine and gilts fed diets devoid of ractopamine. Both subjective and objective belly firmness measurements were increased (P < .01) in gilts fed diets containing CLA as compared to gilts fed diets containing no CLA. Within the added fat treatment, gilts fed diets containing CWG had higher (P < .04) objective belly firmness scores compared to gilts fed diets containing BT.

Discussion

The results of this research support previous research in which feeding diets containing added fat increases feed conversion efficiency. The enhancement in growth efficiency was not different between the two fat types used in this study which demonstrates that the two fat sources are comparable to one another in terms of the improvement in growth performance realized. Feeding 5% added fat to genetically lean gilts increases carcass weight without affecting the predicted percentage lean in the carcass. As expected, feeding gilts diets containing ractopamine increased growth performance and carcass content. Feeding diets containing CLA increased belly quality in this trial which supports results from previous research carried out in the Animal Sciences Department. In addition, CLA enhanced feed efficiency and increased the predicted percent lean in the population of lean gilts which were used in this trial.

Implications

The results of this research demonstrate that feeding diets containing added fat to genetically lean gilts, either in the form of beef tallow or choice white grease, increases production efficiency and increases the pounds of pork produced per pig. Adding ractopamine and CLA to the diets of lean gilts improves growth efficiency and enhances carcass characteristics.

References

Dugan, M. E. R., J. L. Aalhus, A. L. Schaeffer, and J. K. G. Kramer. 1997. The effect of conjugated linoleic acid on fat to lean repartitioning and feed conversion in pigs. Can. J. Anim. Sci. 77: 723-725.

Herr, C. T., D. C. Kendall, K. A. Bowers, S. L. Hankins, T. E. Weber, A. P. Schinckel, and B. T. Richert. 2001. Effect of a step-up or step-down ractopamine sequence for late-finishing pigs. J. Anim. Sci. 79: 23 (Abstr.).

NPPC. 1991. Procedures to Evaluate Market Hogs (3^rd Ed.). National Pork Producers Council, Des Moines, IA.

NPPC. 1999. Pork Quality Standards. National Pork Producers Council, Des Moines, IA.

Schinckel, A. P., J. M. Eggert, B. T. Richert, and A. L. Carroll. 2000. Effects of conjugated linoleic acid supplementation on pig growth, pork quality, and carcass composition in two genetic populations of gilts. Purdue University Swine Day Report. p 51-53.

Seerley, R. W., J. P. Briscoe, and H. C. McCampbell. 1978. A comparison of poultry and animal fat on performance, body composition and tissue lipids of swine. J. Anim. Sci. 46: 1018-1023.

Stahly, T. S. and G. L. Cromwell. 1979. Effect of environmental temperature and dietary fat supplementation on the performance and carcass characteristics of growing and finishing swine. J. Anim. Sci. 49: 1478-1488.

Table 1. Composition of experimental diets (as-fed basis)

^aThe added fat diets contained 5% choice white grease or 5% beef tallow
^bIn diets containing conjugated linoleic acid (CLA) 1% of a product consisting of 60% CLA isomers replaced soybean oil
^cProvided per lb of complete diet: vitamin A, 1,650 IU; vitamin D₃, 165 IU; vitamin E, 12.0 IU; Menadione, 0.55 mg; vitamin B₁₂, 0.01 mg; riboflavin, 1.92 mg; pantothenic acid, 6.0 mg; and niacin, 8.64 mg
^dProvided per lb of complete diet in phase 1: Fe, 43.99 mg; Zn, 43.99 mg; Mn, 5.45 mg; Cu, 4.08 mg; and I, 0.15 mg
^eProvided per lb of complete diet in phase 2: Fe, 38.49 mg; Zn, 38.49 mg; Mn, 4.76 mg; Cu, 3.57 mg; and I, 0.13 mg
^fProvided 0.14 mg Se per lb of complete diet
^gProvided 20.0 mg tylosin per lb of complete diet
^hIn diets containing ractopamine•HCl the premix, which was added at the expense of corn provided 9 g ractopamine•HCl per ton of complete diet

Table 2. Growth performance (wk 4 to 8) of lean gilts fed diets containing conjugated linoleic acid (CLA) or soybean oil (SBO) with 5% choice white grease (CWG), 5% beef tallow (BT), or 0% added fat with or without ractopamine•HCl (RAC)

Table 3. Contrast P-values for growth performance wk 4 to 8

^aRepresents the contrast for the interaction between ractopamine (Rac) and CLA treatments
^bRepresents the contrast for the interaction between Rac and added fat treatments
^cRepresents the contrast for the interaction between CLA and added fat treatments

Table 4. Growth performance of genetically lean gilts fed diets containing conjugated linoleic acid (CLA) or soybean oil (SBO) with 5% choice white grease (CWG), 5% beef tallow (BT), or 0% added fat with or without ractopamine•HCl (RAC)

Table 5. Contrast P-values for overall growth performance

^aRepresents the contrast for the interaction between ractopamine (Rac) and CLA treatments
^bRepresents the contrast for the interaction between Rac and added fat treatments
^cRepresents the contrast for the interaction between CLA and added fat treatments

Table 6. Carcass characteristics of genetically lean gilts fed diets containing conjugated linoleic acid (CLA) or soybean oil (SBO) with 5% choice white grease (CWG), 5% beef tallow (BT), or 0% added fat with or without ractopamine•HCl (RAC)

^aCarcass lean was calculated using the equation for ribbed carcasses (NPPC, 1991)

Table 7. Contrast P-values for carcass characteristics

^aRepresents the contrast for the interaction between ractopamine (Rac) and CLA treatments
^bRepresents the contrast for the interaction between Rac and added fat treatments
^cRepresents the contrast for the interaction between CLA and added fat treatments

Table 8. Quality characteristics of longissimus dorsi muscle and bellies of genetically lean gilts fed diets containing conjugated linoleic acid (CLA) or soybean oil (SBO) with 5% choice white grease (CWG), 5% beef tallow (BT), or 0% added fat with or without ractopamine•HCl (RAC)

^aSubjective scores were used to evaluate color (1 = pale, pinkish gray; 6 = dark, purplish red; NPPC, 1999)
^bSubjective scores were used to evaluate marbling (1 = devoid to practically devoid; 6 = moderately abundant or greater; NPPC, 1999)
^cCarcass firmness was evaluated using subjective scores (1 = very soft; 5 = very firm; NPPC, 1991)
^dSubjective belly firmness scores were assigned by centrally placing the bellies over a horizontal bar (1 = soft; 5 = firm)
^eObjective scores were assigned to the bellies by measuring the distance between the anterior and posterior ends of the belly when suspended over a horizontal bar

Table 9. Contrast P-values for longissimus dorsi and belly quality characteristics

^aRepresents the contrast for the interaction between ractopamine (Rac) and CLA treatments
^bRepresents the contrast for the interaction between Rac and added fat treatments
^cRepresents the contrast for the interaction between CLA and added fat treatments

Index of 2001 Purdue Swine Research Articles