J. Anim. Sci. 2002. 80:3230-3237
© 2002 American Society of Animal Science
Effect of vitamin E on improving fresh pork quality in Berkshire- and Hampshire-sired pigs1
J. L. Hasty,
E. van Heugten*,2,
M. T. See* and
D. K. Larick
,3
* Department of Animal Science and
and
Department of Food Science, North Carolina State University, Raleigh 27695
2 Correspondence:
Box 7621 (phone: 919-513-1116; fax: 919-515-6316; E-mail:
Eric_vanHeugten{at}ncsu.edu).
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Abstract
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This study was designed to evaluate the effects of vitamin E supplementation on pork quality of two genotypes with distinct differences in pork quality traits. Pigs (n = 240; BW = 87 ± 0.35 kg) were allotted by weight to one of 20 treatments (4 pens/treatment, 3 pigs/pen) in a 2 x 2 x 5 factorial randomized complete block design. Factors included 1) genotype (Berkshire or Hampshire sired), 2) sex (gilts or barrows), and 3) vitamin E level (12.1, 54.7, 98.8, 174.0, and 350.6 IU of vitamin E/kg diet). Hampshire-sired pigs had greater average daily gain (1.05 vs 0.98 kg) and gain:feed (0.30 vs 0.27) and less average daily feed intake (ADFI) (3.46 vs 3.62 kg) than Berkshire-sired pigs (P < 0.001) for the 6-wk study. Hampshire-sired barrows consumed more feed (3.54 vs 3.38 kg/d) and were less efficient (0.29 vs 0.31) than Hampshire-sired gilts (P < 0.05), but this sex difference was not observed in Berkshire-sired pigs (interaction, P < 0.05). Berkshire-sired pigs had greater backfat (34.1 vs 21.1 mm; P < 0.001), reduced longissimus muscle area (37.6 vs 46.3 cm2; P < 0.001), reduced lean percentage (53.0 vs 55.8; P < 0.001), and a greater head-on yield (79.8 vs 79.2; P < 0.05). Vitamin E increased (P < 0.05) ADFI linearly (P < 0.05), but had no effects on carcass composition. Loin chops from Hampshire-sired pigs had reduced ultimate pH (5.64 vs 5.91), greater drip loss (92.2 vs 66.3 mg), and increased Minolta L* (52.6 vs 48.6), a* (8.9 vs 7.5), and b* (6.9 vs 5.2) values compared to Berkshire-sired pigs (P < 0.001). Vitamin E had no effect on pH, temperature, drip loss, and L* or a* values, but tended (P < 0.07) to increase b* values linearly (P < 0.06). Oxidation as indicated by thiobarbituric acid reactive substances (TBARS) was greatest in Hampshire-sired gilts at the lowest level of vitamin E, and decreased linearly (P < 0.001) with additional vitamin E. However, TBARS responded in a cubic fashion (P < 0.05) to vitamin E in Hampshire-sired barrows and were not affected in Berkshire-sired gilts or barrows (three-way interaction, P < 0.02). Hampshire-sired pigs had greater TBARS than Berkshire-sired pigs (0.053 vs 0.047 mg malondialdehyde equivalents/kg). Vitamin E supplementation increased serum concentrations of vitamin E on d 21 (1.06 to 4.79 µg/mL) and d 42 (1.02 to 2.82 µg/mL) and increased tissue concentrations of vitamin E (1.99 to 4.83 µg/g) linearly (P < 0.001). Vitamin E supplementation was not effective in improving fresh meat quality in genotypes with poor or superior meat quality traits.
Key Words: Berkshire • Genotypes • Hampshire • Meat Quality • Pigs • Vitamin E
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Introduction
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Meat quality has become increasingly important to the pork industry as it faces the challenge of improving its presence in the global market. Poor color and inadequate water-holding capacity were the main quality concerns identified by all members of the pork marketing chain (Cannon et al., 1995). Several studies have demonstrated that long-term dietary supplementation of vitamin E to swine decreased drip loss (Asghar et al., 1991; Monahan et al., 1994; Lauridsen et al., 1999) and improved color (Asghar et al., 1991; Monahan et al., 1994), whereas other studies have shown no improvements (Cannon et al., 1996; Jensen et al., 1997; Hoving-Bolink et al., 1998). However, the oxidative stability of pork has been consistently improved by vitamin E supplementation in these studies. Vitamin E may improve pork quality through its antioxidant properties by protecting cell membranes from damage and subsequent fluid loss and by stabilizing color pigments in meat (Buckley et al., 1995), and this effect may differ amongst different genotypes. Consumer-driven selection for lean pork has led to a reduction in intramuscular levels of fat and pork quality (Lonergan et al., 2001). In addition, an increase in the percentage of polyunsaturated fatty acids in muscle membranes has been reported in leaner pigs compared to fatter pigs (Wood and Enser, 1997). Thus, we hypothesize that the effect of vitamin E on pork quality may be different in pigs depending on their genetic background and their propensity for poor pork quality. Therefore, the objective of this study was to evaluate the effects of dietary supplementation with multiple levels of vitamin E on pork quality of genotypes with distinct differences in pork quality traits.
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Materials and Method
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Animals and Treatments
The experimental protocols used in this study were approved by the North Carolina State University Institutional Animal Care and Use Committee. Pigs of the desired genotype were obtained from 27 sows (line C22, PIC, Franklin, KY), which had been inseminated with semen from one of four Berkshire boars, and 27 sows that were inseminated with semen from one of four Hampshire boars. At weaning, Berkshire x PIC and Hampshire x PIC barrows and gilts (n = 240) were blocked by weight within sex and genotype and randomly assigned within block to one of 20 treatments (4 pens per treatment, 3 pigs per pen) in a 2 x 2 x 5 factorial randomized complete block design. Factors included genotype (Berkshire sired or Hampshire sired), sex (gilts or barrows), and level of vitamin E (0, 75, 150, 300, and 600 mg 
-tocopheryl acetate/kg of feed). Pigs were housed at the North Carolina State University Swine Evaluation Station, Clayton, NC. Pens were solid-floor design and provided 1.86 m2 per pig. The basal diet was a corn and soybean meal diet that contained 2.5% added poultry fat, 0.83% lysine, and 22 IU of vitamin E/kg feed (Table 1
). Pigs were started on the experimental diets at an initial BW of 87 ± 0.35 kg and were allowed ad libitum access to the diets for the 6-wk experimental period. Pigs were weighed at the initiation of the study and prior to slaughter. Feed intake was recorded throughout the study. Blood samples were taken by venipuncture from one randomly selected pig (the same pig each time) per pen at the initiation of the study, on d 21, and on d 42. Blood was centrifuged at 830 x g, and serum was collected and stored at -7°C until it was analyzed for vitamin E.
Meat Quality Measurements
Pigs were transported to a commercial slaughter plant in four groups of 60 pigs (by replicate and treatment) 1 wk apart. Hot carcass weights (head on), temperature (Traceable thermometer, Fisher Scientific, Fair Lawn, NJ), and pH (pH*K21, NWK-Binar GmbH, Landsberg, Germany) were determined 45 min and 24 h after slaughter. After 24 h, the right loin was collected from each pig, and one chop, approximately 2.5 cm thick, was collected at the 10th rib location. One additional chop was collected from one previously selected pig per pen (20 pigs per group) and vacuum packaged using a commercial Multi-vac vacuum sealer and frozen at -20°C for subsequent analysis of thiobarbituric acid reactive substances (TBARS) and vitamin E. The first chop was allowed to bloom for approximately 15 min, at which time drip loss was determined using the filter paper method as descibed by Kauffman et al. (1986). Briefly, a circular piece of filter paper (Schleicher and Schuell, Keene, NH), 4.5 cm in diameter, was placed on the chop for 2 s, and drip loss was determined from the difference in dry and wet filter paper weight. The same chop from each loin was used to measure the longissimus muscle area (LMA) by tracing the loin eye using acetate paper, backfat depth using a ruler, and color using a Minolta Chromameter (CR-200, Minolta USA, Ramsey, NJ). The chromameter was set to D65 illuminant using a 0° viewing angle and an 8-mm diameter viewing area, and was calibrated with a white standard color plate. Color measurements were taken in triplicate (in three different areas of the loin muscle) for each pork chop.
Chemical Analyses
Vacuum-packaged loin samples were removed from the -20°C freezer and thawed overnight in refrigerated storage for the analysis of TBARS as a measure of oxidative rancidity, as described by Witte et al. (1970). Excess fat was removed and samples were ground twice using an Oster heavy-duty food grinder and sausage maker (Sunbeam, Delray Beach, FL). Two grams of sample were homogenized in an Omni mixer for 10 s with 8 mL of 50 mM phosphate buffer (pH = 7.0) containing 0.1% EDTA (Fisher Scientific) and 0.1% propyl gallate (Sigma, St. Louis, MO). Two milliliters of a 30% trichloroacetic acid (Fisher Scientific) mixture was added to the sample and homogenized for 20 s. Homogenates were filtered using filter paper (P8; Fisher Scientific) into beakers. Two milliliters of the clear supernatant was mixed with 2 mL of 2-thiobarbituric acid (Sigma), vortexed, and incubated in a boiling water bath for 20 min. Samples were then cooled immediately in an ice bath. Absorbance of samples was read at 533 nm using a spectrophotometer (model DU 640, Beckman, Fullerton, CA), and TBARS were expressed as milligrams of malondialdehyde (MDA) equivalents/kilogram sample. Solutions of 1, 1, 3, 3 tetraethoxypropane (Sigma) at concentrations of 40 x 10-7, 20 x 10-7, 10 x 10-7, 8 x 10-7, 4 x 10-7, and 2 x 10-7 M were used as a standard for MDA equivalents.
Serum and tissue vitamin E concentrations were determined using HPLC, which was comprised of an in-line degasser, controller (600), autosampler (717-plus; 20-µL loop), and photodiode array detector (996) (Waters; Milford, MA). The column used was an Ultremex 3 silica (75 x 4.6 mm) column with an Ultremex 3 silica guard column (30 x 4.6 mm) (Phenomenex; Torrance, CA). Flow rate was 1.5 mL/min with an attenuation of 6 min. Mobile phase consisted of filtered isooctane (HPLC Grade, Fisher) with 1.5% tetrahydrofuran (HPLC grade, Fisher). Standards were prepared at concentrations of 100, 50, 25, 12.5, and 6.25 µg of -tocopherol/mL of isooctane, using a standard that contained 67% -tocopherol.
Serum collected on d 0, 21, and 42 was analyzed for vitamin E using a procedure modified from Bieri et al. (1979). Samples were thawed and 0.5 mL of sample was pipeted into a 13- x 100-mm tube (kept on ice in minimal light) and mixed with 4 mL of 1% L-ascorbic acid (Fisher) in absolute ethanol (200 proof, AAPER Alcohol and Chemical Co., Shelbyville, KY). Samples were vortexed, 2.0 mL of hexane (HPLC Grade, Fisher) was added, and samples were vortexed again for 1 min. Tubes were centrifuged at 15°C for 10 min at 830 x g. Hexane layers were transferred to a clean 10- x 75-mm test tube, kept on ice, and protected from light between extractions. Another 2.0 mL of hexane was added to the samples, and they were vortexed for 2 min. The samples were centrifuged at 15°C for 5 min at 830 x g. Hexane layers were transferred and combined with the first hexane layer. Tubes were dried under a stream of pure nitrogen. Isooctane (0.125 mL) was used to dissolve the samples to be analyzed using HPLC.
Tissue samples were analyzed for vitamin E concentration using a modified procedure of Zaspel and Saari Csallany (1983). Excess fat was removed from the chop, which was then ground twice using an Oster heavy duty food grinder and sausage maker (Sunbeam). Tissue (0.5 g) was placed into a 16- x 150-mm tube to which 5.0 mL of 1% ascorbic acid in absolute ethanol was added. Samples were homogenized for 1 min using a Polytron explosion-proof homogenizer. The remainder of the procedure was the same as that described for serum except that samples were dissolved in 1 mL of isooctane before HPLC analysis.
Dietary -tocopherol acetate concentrations were determined by Roche Vitamins, Inc. (Belvidere, NJ) using HPLC. Samples were ground, soaked in 50 mL of deionized water at 65°C for 10 min, and then extracted using 50 mL of ethyl alcohol and 150 mL of petroleum ether for 45 to 60 min. Fifteen milliliters of the petroleum ether layer was then brought to a volume of 25 mL with isooctane before injection into the HPLC.
Statistical Analyses
Data were analyzed as a randomized complete block design with a 2 x 2 x 5 factorial arrangement of 20 treatments using the general linear models procedures (SAS Inst., Inc., Cary, NC). The model for growth performance, carcass data, pork quality measurements, and muscle vitamin E included sex, genotype, vitamin E, and all their interactions where appropriate. For growth performance traits, starting weight was included as a covariate to adjust for weight differences at the beginning of the feeding period. For carcass traits, final weight for the feeding period was included as a covariate to adjust for weight differences at slaughter. Orthogonal contrasts were used to evaluate linear, quadratic, and cubic effects of vitamin E supplementation (Steel and Torrie, 1980). Serum vitamin E concentrations were analyzed using the mixed model procedure of SAS. The model included sex, genotype, vitamin E, sampling day, and all appropriate interactions. Pen served as the experimental unit for all measurements.
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Results and Discussion
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Growth Performance and Carcass Characteristics
Analyzed levels of vitamin E in the feed were 12.1, 54.7, 98.8, 174.0, and 350.6 IU/kg for the 0, 75, 150, 300, and 600 IU/kg supplementation groups, respectively. Although these levels were substantially lower than anticipated, they provided a wide enough range of vitamin E supplementation to determine potential effects on pork quality. The reason for this discrepancy is not clear. Feed analysis consistently resulted in vitamin E levels that were 56% of the targeted value, which may point to a mixing error rather than analytical error. The vitamin E premix that was used contained 500,000 IU of vitamin E/kg and was blended down to contain 50,000 IU of vitamin E/kg to provide a greater inclusion level in the final diet and enhance mixing accuracy. An error in creating this basemix could explain the consistently lower levels of vitamin E found in the final diets. Dove and Ewan (1991) reported that 93% of the -tocopheryl acetate that was added to complete feeds remained after 90 d of storage at 23 to 26°C. Feed samples obtained from feeds used in this experiment were obtained from multiple locations in the feed batch and were stored in refrigerated storage for less than 6 mo prior to analysis.
A three-way interaction was observed between sex, genotype, and vitamin E level (P < 0.05) for ADG (data not shown). Hampshire-sired gilts had the greatest numerical ADG compared to other pigs when no vitamin E was supplemented above basal levels, whereas Hampshire-sired barrows had the greatest numerical ADG when vitamin E was supplemented at the analyzed level of 174.0 IU/kg. No clear explanation for this interaction is evident, and it is unlikely that this observation is biologically relevant. Hampshire-sired pigs gained weight an average of 6.9% faster (P < 0.001) than Berkshire-sired pigs over the 6-wk feeding period (Table 2). A sex x genotype interaction was observed for ADFI and gain:feed (P < 0.05). Gilts with the Hampshire background consumed less feed (P < 0.05) compared to their barrow counterparts; however, no sex difference was observed for the Berkshire-sired pigs. Similarly, gain:feed was greater (P < 0.05) in Hampshire-sired gilts compared to Hampshire-sired barrows, but this difference was not evident within the Berkshire cross. Overall, Hampshire-sired pigs were superior in their growth performance and carcass traits as indicated by a greater ADG, gain:feed ratio, LMA, lean percentage, and a reduced backfat depth (P < 0.001), although carcass yield appeared to be reduced (P < 0.05). These data are in agreement with those reported by Goodwin and Burroughs (1995), who observed Hampshire-sired pigs to have improved feed efficiency, reduced backfat depth, increased LMA, and improved lean percentage compared to Berkshire-sired pigs. As expected, gilts were more efficient (P < 0.01), had reduced backfat depth (P < 0.001), had greater LMA (P < 0.01), and tended (P < 0.10) to have a greater lean percentage in the carcass than barrows.
Supplementation of -tocopheryl acetate to the diet tended (P < 0.10) to affect ADG and gain:feed in a cubic fashion (P < 0.05), and increased (P < 0.05) ADFI in a linear (P < 0.05) manner over the 6-wk supplementation period (Table 3). Amer and Elliot (1973), Monahan et al. (1990b), and Cannon et al. (1996) reported no effect on growth performance with supplementation of vitamin E. In contrast, Asghar et al. (1991) observed improvements in the early stages for growth and feed efficiency when pigs were supplemented with 100 and 200 IU of vitamin E/kg feed. Supplementation of -tocopheryl acetate to the diet had no effect (P > 0.45) on yield percentage (head-on), backfat thickness, loineye area, or lean percentage (Table 3). In agreement with these results, Asghar et al. (1991) and Cannon et al. (1996) reported no differences in carcass yield or carcass characteristics in pigs supplemented with vitamin E compared to control pigs.
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Table 3. Main effect means of dietary supplementation of vitamin E on growth and carcass characteristics of Berkshire-sired pigs and Hampshire-sired pigsa
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Pork Quality
No interactive effects between genotype, sex, and vitamin E supplementation (P > 0.10) were observed for any of the pork quality traits measured in this study; therefore, only main effects of genotype and vitamin E supplementation are reported. No differences between genotypes were detected for initial pH or temperature; however, ultimate pH was reduced by 0.27 units (P < 0.01) in Hampshire-sired pigs compared to Berkshire-sired pigs (Table 4). Goodwin and Burroughs (1995) and van Laack et al. (2001) reported reductions in ultimate pH of 0.21 and 0.10 units, respectively, in Hampshire-sired pigs compared to Berkshire-sired pigs. Ultimate pH has been suggested to be an indicator of meat quality, with a low pH being indicative of inferior quality pork (Bendall and Swatland, 1988). Indeed, Hampshire-sired pigs in the current study had greater drip loss (P < 0.001) and increased (P < 0.001) Minolta L*, a*, and b* values (indicating lighter, more red, and more yellow pork, respectively) in loin chops collected 24 h postmortem when compared to Berkshire-sired pigs. Similarly, Goodwin and Burroughs (1995) reported that pork chops from Hampshire-sired pigs were lighter in color and had increased drip loss compared to Berkshire-sired pigs. Goerl et al. (1995) noted that the longissimus muscle of Hampshire pigs was lighter, more yellow, and more red compared to that of low lean-growth pigs that had only been selected for reproductive traits. Other studies have reported low ultimate pH, pale color, and increased drip loss in meat from pigs carrying the Rendement Napole (RN-) gene, which is predominant in the Hampshire breed (Monin and Seiller, 1985; Hamilton et al., 2000). Although we did not evaluate the prevalence of this gene in the populations studied, the reductions in pork quality we observed in Hampshire-sired pigs are consistent with these previously published reports.
Dietary supplementation of vitamin E had no effect on pH or temperature when measured at either 45 min or 24 h after slaughter (Table 4
). These results are comparable to those of Cannon et al. (1996), Houben et al. (1998), and Hoving-Bolink et al. (1998), who reported no improvements in pH due to vitamin E supplementation. In contrast, Lauridsen et al. (1999) reported increased ultimate pH in pigs fed 200 mg of DL--tocopheryl acetate/kg compared to pigs supplemented with 0 or 100 mg of DL--tocopheryl acetate/kg feed. However, a difference in pH would not be expected because vitamin E has not been reported to have a direct effect on glycolytic potential or postmortem glycolysis. Drip loss was not affected by supplementation of -tocopheryl acetate to the diet. This is in agreement with Cannon et al. (1996), who reported no effect of vitamin E supplementation on drip loss in fresh loin chops. In contrast, Lauridsen et al. (1999) observed a reduction in drip loss in longissimus and psoas major samples when measured following slaughter. Cheah et al. (1995) also reported decreased drip loss with supplementation of 500 IU of vitamin E/kg of diet following slaughter in longissimus thoracis, but not masseter muscle samples.
There were no effects of supplementation of -tocopheryl acetate to the diet on L* or a* values; however, there was a tendency (P < 0.07) for vitamin E to increase b* values linearly (P < 0.06), indicating increased yellowness. Asghar et al. (1991) reported an increase in redness of fresh pork when vitamin E was supplemented at 200 IU/kg; however, no effects on lightness or yellowness of pork were observed. Others (Cannon et al., 1996; Houben et al., 1998; Zanardi et al., 1999) observed no effects of vitamin E supplementation on color of fresh pork.
Vitamin E has strong antioxidant properties and has been proposed to stabilize muscle membranes, which in turn can decrease the development of rancidity, improve color, and reduce drip loss (Buckley et al., 1995). However, effects of vitamin E supplementation on pork quality have been variable (reviewed by Pettigrew and Esnaola, 2000). van Laack and Spencer (1999) reported differences in the fatty acid composition of phospholipids from longissimus muscle in different genotypes, which may affect sensitivity to oxidation, membrane stability, and subsequent meat quality. Previous research (Monahan et al., 1992) suggested that differences in fatty acid composition of phospholipids from muscle of pigs fed soy oil or tallow resulted in changes in oxidation and flavor of meat. We hypothesized that some of the variation in response to vitamin E reported in the literature may be due to the genetic background of pigs studied and that effects of vitamin E on pork quality may be observed primarily in genotypes with inherent pork quality problems. Pigs used in the present study represented two populations with distinct differences in pork quality attributes, and we demonstrated a substantial reduction in ultimate pH, increased drip loss, and paler, more yellow and red pork in Hampshire-sired pigs compared to Berkshire-sired pigs. Other studies (Goodwin and Burroughs, 1995; van Laack et al., 2001) have reported similar results; therefore, our experimental model to assess pork quality was sensitive enough to distinguish true differences in pork quality. However, supplementation with vitamin E for 6 wk prior to slaughter did not affect pork quality measurements in either population and was not effective in preferentially improving pork quality in pigs with a propensity for poor meat quality. Cheah et al. (1995) observed reductions in drip loss when vitamin E was supplemented at 500 IU/kg for 46 d, and this effect was not different between PSE-prone halothane carriers and halothane-negative pigs.
Oxidative Stability and Vitamin E Concentrations
A three-way interaction (P < 0.02) was observed for TBARS concentrations in loin muscle samples taken 24 h after slaughter (Table 5). Hampshire-sired gilts had the greatest levels of TBARS compared to other pigs when the lowest level of vitamin E was present, and this level decreased linearly (P < 0.001) with additional vitamin E. Levels of TBARS responded in a cubic fashion (P < 0.05) with the addition of vitamin E in Hampshire-sired barrows and were not affected in Berkshire-sired gilts or barrows. Hampshire-sired pigs had greater levels of TBARS compared to Berkshire-sired pigs (0.053 vs 0.047 mg of MDA/kg), which may be related to possible differences in the fatty acid composition of phospholipids in muscle as reported by van Laack and Spencer (1999). There were no overall differences in TBARS concentrations with increasing levels of vitamin E in the diet. Other reports (Jensen et al., 1997; Hoving-Bolink et al., 1998; Lauridsen et al., 1999) have consistently reported improvements in the oxidative stability of muscle with suppementation of vitamin E. However, the greatest effects of vitamin E supplementation has been typically observed in meat with increased susceptibility to oxidation, such as display storage or prolonged frozen storage. Oxidation of loin samples in the present experiment was minimal as evidenced by the low TBARS values; therefore, the opportunity for vitamin E to exert a protective effect may have been limited. Gray and Pearson (1987) suggested a threshold value of 1 mg of MDA/kg tissue for organoleptic detection of rancid flavor, which is well above the values observed in the present study. The only effect of vitamin E on oxidative stability was observed in muscle from Hampshire-sired gilts. Level of oxidation in muscle from these pigs was greater when diets contained basal levels of vitamin E compared to other pigs and decreased linearly with vitamin E supplementation to levels similar to the other groups.
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Table 5. Interactive effects between genotype, sex, and vitamin E supplementation on oxidative stability (mg of malondialdehyde/kg) of fresh loin musclea
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Serum concentrations of vitamin E at the initiation of the experiment were similar and increased linearly with increasing levels of vitamin E on d 21 (P < 0.001) and d 42 (P < 0.001) of supplementation (Table 6). Vitamin E concentrations in the serum were not affected by genotype. Others researchers have reported increased serum vitamin E concentrations when vitamin E was supplemented through the feed (Jensen et al., 1988; Monahan et al., 1990a, b; Asghar et al., 1991) or water (van Heugten et al., 1997). Soler-Velasquez et al. (1998) observed a quadratic increase over time in serum -tocopherol concentrations with increasing levels of dietary vitamin E, (0, 50, 125, and 200 mg all-rac--tocopheryl acetate/kg), for d 7, 14, 21, 28, and 35.
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Table 6. Main effect means of genotype and dietary supplementation of vitamin E on serum and loin muscle vitamin E concentrationsa
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Tissue concentrations of vitamin E increased linearly (P < 0.01) with increasing levels of supplementation (Table 6). Cannon et al. (1996), Jensen et al. (1997), and Lauridsen et al. (1999) reported increases in -tocopherol in the longissimus muscle with increasing levels of dietary vitamin E when supplemented throughout the growing-finishing period. In spite of the short period of vitamin E supplementation used in the present study (42 d), tissue vitamin E concentrations were increased to levels similar to those reported in these previous studies. Cheah et al. (1995) supplemented pigs with 500 IU of vitamin E/kg of diet for 46 d and reported vitamin E concentration in longissimus muscle to increase from 0.89 to 4.37 mg/kg. Faustman et al. (1989) indicated that color and shelf life of beef could be maintained with an -tocopherol concentration of 3.0 to 3.7 mg/kg of tissue. In pigs, the minimum concentration of vitamin E in muscle to affect pork quality has not been identified. In the present study, supplementation with vitamin E resulted in loin -tocopherol concentrations of up to 4.83 mg/kg, but this did not impact fresh pork quality.
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Implications
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Pork quality characteristics can be improved by genetic selection. The present study clearly demonstrates that pork quality in Berkshire-sired pigs was superior compared to Hampshire-sired pigs. Dietary supplementation of vitamin E increased loin muscle vitamin E concentrations, but did not affect fresh pork quality characteristics in either genotype. Therefore, the strategic use of vitamin E to improve fresh pork quality in pigs that have inherent pork quality problems or to further enhance fresh pork quality in pigs with superior pork quality does not appear to be effective.
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Footnotes
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1 We acknowledge the Institute of Nutrition of the University of North Carolina Systems and D. R. Campbell and Roche Vitamins, Inc. (Nutley, NJ). The authors wish to thank O. Phillips and L. Xi for technical support, K. Dorton and N. Leadbetter for laboratory assistance, and J. Pope for animal care. The use of trade names does not imply endorsement by the North Carolina Agricultural Research Service of the products named or criticism of similar ones not mentioned. 
3 Present address: Graduate School, 205 Peele Hall, NC State Univ.
Received for publication April 8, 2002.
Accepted for publication July 15, 2002.
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Abstract
Introduction
