Key Words: Chilling, Exudative Meat, Halothane Susceptibility, Meat Quality, Vitamin E

Transcription

1 Vitamin-mineral supplementation and accelerated chilling effects on quality of pork from pigs that are monomutant or noncarriers of the halothane gene 1 C. R. Kerth* 2, M. A. Carr*, C. B. Ramsey*, J. C. Brooks*, R. C. Johnson, J. E. Cannon, and M. F. Miller* *Animal Science and Food Technology Department, Texas Tech University, Lubbock ; Triumph Pork Group, LLC, Denison, IA 51442; and DEKALB Choice Genetics, St. Louis, MO ABSTRACT: We examined the effects of vitamin and mineral supplementation of the finishing diet on growth and accelerated chilling of carcasses on carcass and muscle traits of halothane gene carrier and noncarrier pigs. Barrows and gilts that were either monomutants (MON, n = 49) or noncarriers (NON, n = 28) of the halothane gene were fed a standard finishing diet until they reached 86 kg. They then were randomly assigned to one of four finishing diets formulated to contain 11 IU/kg vitamin E (0), 311 IU/kg vitamin E plus additional vitamins and minerals (300), 611 IU/kg vitamin E plus additional vitamins and minerals (600), or 911 IU/kg vitamin E plus additional vitamins and minerals (900) until they were slaughtered (118 kg). Alternating carcass sides were assigned either a normal chilling procedure (NC, 4 C for 24 h) or an accelerated chilling procedure (AC, 20 C for 1.5 h and then 4 C for 22.5 h). Supplementing vitamin E in the finishing diet increased (P < 0.05) the concentration of vitamin E in the longissimus muscle. Supplementing vitamin E in the diets of MON pigs did not affect color, firmness, or cooking losses of loins or color and firmness of hams. For the NON genotype, increasing the level of vitamin E in the diet decreased (P < 0.05) the percentage of PSE loins and hams. Color and firmness scores of the gluteus medius and longissimus muscles were improved 0.4 unit (P < 0.005) by AC compared with NC of carcasses. Loin chop juiciness and flavor were improved (P < 0.05) in the MON genotype for AC compared to NC. Accelerated chilling reduced (P < 0.05) the percentage of PSE loins from 38 to 17% and PSE hams from 32 to 10% for the MON genotype, but percentage of PSE was not affected (P > 0.05) by chilling treatment for the NON genotype. No interaction between diet and chill treatments existed for muscle quality traits (P > 0.05). Supplementing finishing diets of NON pigs with at least 600 IU/kg vitamin E, in addition to other vitamins and minerals, or accelerated chilling of MON carcasses can reduce the incidence of PSE pork. Key Words: Chilling, Exudative Meat, Halothane Susceptibility, Meat Quality, Vitamin E 2001 American Society of Animal Science. All rights reserved. J. Anim. Sci : Introduction Processing and retail marketing of PSE pork is the cause of nearly $30 million of economic loss to the pork industry because of poor color, processing characteristics, and cooking yields (Meeker and Sonka, 1994). Numerous nutritional and processing treatments have been evaluated for their effectiveness in reducing the incidence of PSE pork. Cannon et al. (1996) and Mona- 1 This study was supported by a grant from the BASF Corp. Special thanks go to Bart Cousins for his assistance in formulating the diets used in this experiment. 2 Correspondence should be addressed: current address: Anim. and Dairy Sci. Dept. and Auburn Univ., 140 Upchurch Hall, Auburn, AL (phone: ; fax: ; ckerth@ acesag.auburn.edu). Received August 17, Accepted April 24, han et al. (1993) reported that feeding vitamin E reduced lipid oxidation but did not affect pork longissimus color. Others have shown that supplementing swine finishing diets with supplemental vitamins (specifically vitamin E) and minerals (Ramsey et al., 1995) or accelerated chilling of carcasses (Frederick et al., 1993; Owen et al., 1995; Springer, 1997) helped to reduce the incidence of the PSE condition. However, neither the minimum level of vitamin E required to improve meat quality nor the effects of vitamin E supplementation of the finishing diet in combination with accelerated chilling has been established. Because supplementation of the diet with vitamin E and accelerated chilling have reduced the incidence of PSE pork, it is hypothesized that the combination of both treatments would have an additive effect. The objective of this study was to determine the minimum level of supplemental vitamin E with other vitamins and minerals in addition to accelerated chilling of pork carcasses on carcass and 2346

2 Pork quality 2347 muscle characteristics and the incidence of PSE muscle. Materials and Methods Animals and Diets. Tissue samples (docked tails) of preweaned pigs originating from a commercial breeding company hybrid (50% Pietrain, 37.5% Large White, and 12.5% Landrace) were collected and the halothane genotype of each pig was identified using the HAL-1843 (Innovations Foundation, Toronto, Canada) DNA test. A grain sorghum/soybean meal complete finishing diet was fed to 33 barrows and 44 gilts that were either monomutants (MON, n = 49) or noncarriers (NON, n = 28) of the halothane gene at the Texas Tech University confinement finishing unit until they reached 86 kg. They then were randomly assigned within the MON and NON groups to one of four finishing diets (Table 1) formulated to contain 11 IU/kg vitamin E (0 IU supplemented vitamin E, control), 311 IU/kg vitamin E (300 IU supplemented vitamin E and additional vitamins and minerals), 611 IU/kg vitamin E (600 IU supplemented vitamin E and additional vitamins and minerals), or 911 IU/kg vitamin E (900 IU supplemented vitamin E and additional vitamins and minerals) until they were slaughtered. The three experimental diets also were supplemented with riboflavin, vitamin C, manganese, copper, zinc, and magnesium. A portion of each mineral was chelated. Pigs across diet and geno- type treatments were divided into two slaughter groups because of differences in time to slaughter weight. One group was fed the experimental diet for 36 d and the other for 70 d. Because all treatments were evenly distributed between the two slaughter groups and because the length of the feeding/finishing period was not intended to be controlled in this study, the variation due to time the pigs were fed the experimental diet was blocked in the statistical analysis. Slaughter. When the pigs from each of the groups reached 114 kg, they were transported to the Texas Tech Meat Laboratory, allowed to rest for 12 h with water available, and humanely slaughtered and dressed following standard procedures. After being weighed and washed, one carcass side was randomly assigned to a normal chilling procedure (NC, 4 C for 24 h) and the opposite side of the same carcass was assigned to an accelerated chilling procedure (AC, 20 C, 0.1 m 3 /s air flow for 1.5 h then 4 C for 22.5 h). Temperature (Sapac TempRecord Reader, Modesto, CA) and ph (Orion, model 230A, Boston, MA) were measured in the semimembranosus muscle in the ham and in the longissimus muscle at the last rib. Temperature was recorded immediately after carcass washing and then hourly for at least 20 h, and ph was recorded hourly for 3 h and at 20 to 24 h postmortem. MeatCheck instrument (MeatCheck model 160, Erfurt, Germany) readings (consisting of electrical impedance measured between two copper probes inserted 2.5 cm into the Table 1. Experimental design and composition of four experimental finishing diets Item 0 a No. of pigs MON b, barrows MON, gilts NON c, barrows NON, gilts Ingredient Milo, % Soybean meal, % Calcium carbonate, % Dicalcium phosphate, % Iodized salt, % Vitamin-TM premix d, % Experimental premix, % Vitamin E, IU/kg (formula/analyzed) 11/ / / /823.8 Riboflavin, mg/kg (formula/analyzed) 3.3/8.2 50/ / /81.7 Vitamin C, mg/kg (formula/analyzed) 0/<10 50/ /56 50/57.0 Selenium, mg/kg Mn, mg/kg / mg/kg chelated 120/30 120/30 120/30 Cu, mg/kg / mg/kg chelated 60/15 60/15 60/15 Zn, mg/kg / mg/kg chelated 120/30 120/30 120/30 Mg, mg/kg / mg/kg chelated 800/ / /100 a Level of supplemental vitamin E/kg provided by the experimental premix. b Monomutant carriers of the halothane gene. c Noncarriers of the halothane gene. d Vitamin-trace mineral premix provided the following per kilogram of ration: vitamin A, 3,858 IU; vitamin D 3, 386 IU; vitamin E, 11 IU; vitamin B 12, 0.02 mg; riboflavin, 3.3 mg; niacin, 16.5 mg; pantothenic acid, 13.7 mg; choline, mg; menadione, 3.3 mg; Ca, to %; Cu, %; Fe, 0.66%; Mn, %; and Zn, 0.56%. Diet

3 2348 Kerth et al. muscle 2.5 cm apart) were measured in the longissimus muscle at the second lumbar vertebra of the loin and in the semimembranosus muscle of the ham at 24 h postmortem. Carcass Measurements and Fabrication. After the carcasses had chilled for 20 to 24 h, each carcass side was ribbed between the 10th and 11th ribs. Subcutaneous fat thickness was measured along the midline at the first, 13th (to approximate the location where fat is commonly measured in industry settings), and last ribs and last lumbar vertebrae and one-half the distance across the loineye muscle at the 10th rib. Visual muscle score, carcass length, and loineye area measurements were also recorded. Subjective visual scores for color (1 = pale gray, 5 = dark purplish red), firmness (1 = very soft, 5 = very firm), marbling (1 = devoid to practically devoid, 5 = moderately abundant or greater), and muscle condition (1 = pale, soft, and exudative, 2 = red, soft, and exudative, 3 = red, firm, and normal, 4 = dark, firm, and dry) were assigned by trained and experienced personnel to the longissimus muscle at the 10th rib interface and to the gluteus medius muscle at the hamloin interface according to NPPC (1991). Also at 24 h postmortem, values for CIE L* (0 = black, 100 = white), a* (positive values = red, negative values = green), and b* (positive values = yellow, negative values = blue) were measured on the longissimus muscle at the 10th rib interface and the gluteus medius muscle at the hamloin interface using a Minolta CR-200 ChromaMeter (Osaka, Japan). The ChromaMeter was calibrated with a standard white plate and had an 8-mm-diameter viewing area and a 0 viewing angle, and the area was illuminated with CIE D65 lighting conditions using diffuse illumination from a xenon arc lamp. A 4-g sample was taken from the longissimus muscle at the 10th rib, frozen in liquid nitrogen, and analyzed at Oregon State University for vitamin E concentration using the procedure described by Craig et al. (1992). Drip Loss and Sensory Evaluation of Loins. Immediately following fabrication, the longissimus muscle was excised from the 11th rib to the last lumbar vertebra section of the loin. A 1.3-cm-diameter core about 6 cm long was taken from the muscle at the 10th rib, perpendicular to the length of the muscle, weighed, and suspended in a plastic bag for 24 h at 2 C. The muscle sample then was reweighed to determine drip loss as a percentage of the original weight. Five 2.5-cm-thick chops were vacuum-packaged, stored 7 d at 2 C, and frozen ( 20 C) for up to 60 d until they were analyzed. Chops for sensory analyses were thawed at 2 C for 24 h and cooked on Farberware Open Hearth broilers (Bronx, NY) to an internal temperature of 40 C, turned, and cooked until they reached 70 C, removed, cut into 1-cm 3 pieces, and served to an eight-member trained (Cross et al., 1978) sensory panel consisting of meat science faculty and graduate students (AMSA, 1995). Chops were scored on an 8-point scale for initial juiciness, sustained juiciness, initial tenderness, sustained tenderness, flavor intensity, pork flavor, and overall mouthfeel (1 = extremely dry, dry, tough, tough, bland, off-flavor, uncharacteristic of pork; 8 = extremely juicy, juicy, tender, tender, intense, porklike flavor, characteristic of pork). Chops were weighed before and after cooking to determine cooking loss. Statistical Analyses. Data were analyzed using the General Linear Model procedure of SAS (SAS Inst. Inc., Cary, NC) for a split-plot arrangement of a randomized block design. Because pigs reached slaughter weight at different times, and therefore consumed different total amounts of vitamin E, the diet level time fed interaction was evaluated. Because no interaction existed for any trait measured, the time fed variable was included in the model as a block. As a result, any variation due to time the diets were fed was accounted for in the model and a simple diet level effect was analyzed. Genotype (MON or NON) was analyzed in the main plot and chilling method (AC or NC) and diet (0, 300, 600, or 900) were analyzed in the split plot. The block genotype interaction was used as the error term for the main plot. Hours postmortem for temperature and ph were analyzed as repeated measures of the split plot. Significant (P < 0.05) interaction and main effect means were separated using the PDIFF option of LSMEANS. Percentage of loins and hams that were PSE was calculated with the FREQ procedure using the CHISQ option of SAS. Pairwise comparisons of percentages were done according to Ott (1988) for comparing two binomial proportions. Experiment-wise acceptability level for pairwise comparisons was 5%. Results Live Performance and Carcass Traits. Diet did not affect (P > 0.05, Table 2) gain:feed, ADG, live weight, carcass weight, or any carcass trait measured. However, diet did affect (P < 0.001) the concentration of vitamin E in the longissimus muscle. Each increase in vitamin E supplement in the diet increased (P < 0.05) concentration of vitamin E in the longissimus muscle. Genotype of the pigs did not affect (P > 0.05) any live performance traits. However, NON pigs had 0.2 cm more (P = 0.02) backfat at the 10th rib and tended to have more backfat at the first rib (P = 0.08) and 13th ribs (P = 0.07) than MON pigs. All other carcass trait measurements were not affected (P > 0.05) by genotype, diet, or their interaction. Temperature and ph. Carcass chilling method affected postmortem ham and loin temperature (P < 0.05, Figure 1). Temperatures were lower (P < 0.05) in AC hams than in NC hams at every hour postmortem. In addition, temperatures were lower (P < 0.05) in AC loins than in NC loins each hour except for 21 h postmortem, when chilling method no longer affected (P > 0.05) loin temperature. Neither genotype, diet, nor their interactions affected temperature decline in the ham or loin (P > 0.05). A diet genotype interaction affected longissimus muscle ph (P < 0.05, Figure 2). Diet did not affect ph

4 Table 2. Least squares means ± SEM of live performance and carcass traits for diet and genotype main effects Diet Genotype Item P > F MON NON P > F Gain:feed, kg/kg a ± ± ± ± ± ± ADG, kg/d 0.51 ± ± ± ± ± ± Live weight, kg ± ± ± ± ± ± Hot carcass weight, kg 78.1 ± ± ± ± ± ± Dressing percentage 73.5 ± ± ± ± ± ± Cold carcass weight, kg 76.5 ± ± ± ± ± ± Cooler shrink, % 2.2 ± ± ± ± ± ± Carcass length, cm 80.9 ± ± ± ± ± ± Fat thickness, cm First rib 3.4 ± ± ± ± ± ± th rib 2.0 ± ± ± ± ± ± th rib 1.7 ± ± ± ± ± ± Last rib 2.0 ± ± ± ± ± ± Last lumbar vertebra 2.0 ± ± ± ± ± ± Loineye area, cm ± ± ± ± ± ± Muscle score b 6.8 ± ± ± ± ± ± Muscle vitamin E, g/g 4.6 f ± e ± d ± c ± ± ± a Calculated as pen averages. b 6 = average +,7= thick. c,d,e,f Means in a row within a treatment having different superscripts differ (P < 0.05). Pork quality 2349

5 2350 Kerth et al. Figure 1. Effects of carcass chilling method on ham and loin temperature at various times postmortem. in MON loins at 1, 2, 3, or 4 h postmortem. At 1, 2, 3, and 4 h postmortem, NON pigs on the 600 diet had higher (P < 0.05) ph values than all other diet genotype groups. The ph values for NON pigs at 1 h postmortem were higher (P < 0.05) than those for MON pigs regardless of diet. After 2 h, all of the NON genotype loins had a higher (P < 0.05) ph than the MON genotype loins, except that the ph of loins from MON pigs fed the 900 diet did not differ (P = 0.07) from that of loins from NON pigs fed the 0 diet. At 3 h postmortem, all of the NON genotype loins had a higher (P < 0.05) ph than the MON genotype loins, except that the ph of MON loins from pigs fed the either the 300 or 900 diet did not differ (P > 0.05) from the ph of loins from NON pigs fed the 0 diet. At 4 h postmortem, the ph of MON pigs on the 300 diet did not differ (P > 0.05) from either the 0 or 900 diet in the NON genotype and ph of loins from MON pigs on the 900 diet did not differ (P > 0.05) from loins from NON pigs on the 0, 300, or 900 diet. All other NON Figure 2. Least squares means for genotype diet interaction effects on postmortem ph decline in the longissimus muscle at the last rib. MON = monomutants, NON = noncarriers.

6 Pork quality 2351 Figure 3. Least squares means for genotype main effects on postmortem ph decline in the semimembranosus muscle of the ham. MON = monomutants, NON = noncarriers. *Genotype means for ph within each hour postmortem are different (P < 0.05). genotype loins had higher ph values than MON genotype loins (P < 0.05). No differences in ph were found for diet, genotype, or their interaction at 24 h postmortem (P > 0.05). Chilling method did not affect ph at any time postmortem (P > 0.05). Genotype affected postmortem ph decline in the semimembranosus muscle of the ham (P < 0.05, Figure 3). Hams from pigs with the MON genotype had lower (P < 0.05) ph values through 4 h postmortem compared to hams from the NON genotype. Genotype did not affect (P > 0.05) ph at 24 h postmortem. No other main effect or interaction affected ph of the semimembranosus muscle (P > 0.05). Loin Fresh Color, MeatCheck Values, and Cooking Losses. Lean color and firmness of fresh loins were not affected (P > 0.05, Table 3) by diet, genotype, or their interaction. However, AC improved both color and firmness scores by 0.4 unit compared to the NC treatment regardless of genotype (P < 0.005). MeatCheck values were affected by the genotype diet interaction (P < 0.05). Within the MON genotype, pigs on the 0 and 900 diets had higher MeatCheck values (indicating more conductivity and higher quality) than those on the 300 or 600 diets (P < 0.05). In the NON genotype, pigs on the 600 diet had higher (P < 0.05) MeatCheck values than those on the 0 diet, but pigs on the 300 and 900 diets did not differ (P > 0.05) from those on either the 0 or 600 diets. Chilling method did not affect (P > 0.05) MeatCheck values. None of the treatments nor their interaction affected (P > 0.05) L*, a*, or b* values. Loin drip and cooking loss were not affected (P > 0.05) by treatment main effects or their interaction. Carcass chilling method did not affect drip loss or cooking loss of loins (P > 0.05). Ham Fresh Color and MeatCheck Values. Gluteus medius color in the ham was affected by a genotype diet interaction (P < 0.005, Table 3). In the MON genotype, the 600 diet caused lower (P < 0.05) color scores compared to other diets, but in the NON genotype the 0 diet produced lower (P < 0.05) color scores than either the 600 or 900 diets and the 900 diet had the highest (P < 0.05) color score compared to all others. Hams from AC carcasses had higher (P < 0.001) color and firmness scores than NC carcasses. Muscle firmness was not affected by diet, genotype, or their interaction (P > 0.05). MeatCheck values (semimembranosus muscle) were affected by the genotype diet interaction (P = 0.03) and by the chilling method (P = 0.001). Within the MON genotype, the 600 diet produced the lowest (P < 0.05) MeatCheck values compared to the other diets. In the NON genotype, the 0 diet produced a lower (P < 0.05) MeatCheck value than either the 300 or 900 diets but did not differ (P > 0.05) from the 600 diet. The 900 diet produced a higher (P < 0.05) MeatCheck value than all other levels of diet fed to MON pigs and all diet genotype subclasses except the 300 diet fed to NON pigs. In addition, AC hams had higher (P < 0.001) MeatCheck values than NC hams. Genotype, diet, their interaction, and chilling method did not affect (P > 0.05) L*, a*, or b* values. However, the genotype diet interaction approached significance (P = 0.06) for L* values. Similar to visual color, the 600 diet tended to have higher L* values (more white) compared to other diets in the MON genotype. In the NON genotype, 600 and 900 diets

7 2352 Table 3. Least squares means and SEM for a genotype diet interaction and chilling method main effects on color, firmness, colorimeter values, drip loss, and cooking loss for fresh loins and hams MON NON Chill Trait SEM SEM P > F AC NC SEM P > F Loin Color a a 2.3 b Firmness a a 2.2 b MeatCheck b 44.1 e 33.2 f 34.2 f 45.3 e de 56.8 cd 65.5 c 55.0 cd L* a* b* Drip, % Cooking loss, % Ham Color a 2.6 de 2.7 de 2.1 f 2.8 d ef 2.7 de 3.0 d 3.3 c a 2.5 b Firmness a a 2.2 b MeatCheck b 32.4 de 27.6 f 19.1 g 31.2 ef e 49.0 cd 39.2 de 51.5 c a 31.9 b L* a* b* Kerth et al. a 2 = grayish pink or soft, 3 = pinkish gray or slightly firm. b Electrical impedance measured by the MeatCheck probe. c,d,e,f Means in a row within an interaction or main effect treatment having the same or no superscripts do not differ (P > 0.05).

8 tended to have lower L* values compared to 0 or 300 diets and the NON 600 diet tended to have the lowest L* value of all diet genotype groups. The MON genotype tended to produce higher L* values than NON pigs. Incidence of PSE. Percentages of loins visually scored PSE for each genotype within diet are shown in Figure 4. Diet did not affect (P > 0.05) percentage of PSE loins in the MON genotype. However, in the NON genotype, increasing the level of vitamin E beyond 611 IU in the diet decreased (P < 0.05) the percentage of PSE loins. In the MON genotype, the 600 diet resulted in a higher (P < 0.05) incidence of PSE hams than did the 0 diet but did not differ (P > 0.05) from the other diets. In the NON genotype, percentage of PSE hams was decreased (P < 0.01) with an increase in vitamin E level above 311 IU in the diet. No PSE hams were produced if the diet was supplemented with at least 600 IU of vitamin E. In loins, 900 IU was required to eliminate the PSE condition. These results reflect differences found in visual color scores and L* values. Although diet did not affect PSE muscle incidence in the MON genotype, accelerated chilling reduced (P < 0.05, Figure 5) the percentage of PSE loins and hams by 21.4 and 21.9%, respectively, in the MON genotype. Chilling treatment did not affect (P > 0.05) percentage PSE of loins and hams in the NON genotype. Acceler- Pork quality 2353 Figure 5. Percentage of PSE loins and hams for each chilling treatment within genotype. a,b Percentages in each graph having different superscripts differ (P < 0.05). ated chilling is an effective method for reducing the incidence of PSE muscle in pork from MON pigs. Sensory Panel Scores. Diet did not affect (P > 0.05, Table 4) initial juiciness, sustained juiciness, initial tenderness, or flavor intensity of loin chops. Sustained tenderness and overall mouthfeel scores were higher (P < 0.05) for pigs on all of the vitamin and mineralsupplemented diets compared to the 0 diet. Pork flavor scores were higher (P < 0.05) for pigs on the 900 diet than for pigs on the other diets. In the genotype chilling method interaction effects on sensory values of loin chops, scores for initial juiciness, sustained juiciness, and flavor intensity were lower (P < 0.05) for MON pigs that were NC compared to AC or either chill treatment for NON pigs. All other sensory scores of loins were unaffected (P > 0.05) by the genotype chilling method interaction. Discussion Figure 4. Percentage of PSE loins and hams for each genotype within diet. a,b,c,d Percentages in a graph having different superscripts differ (P < 0.05). Studies have shown that the halothane gene causes smaller litter size, slower growth rate, shorter carcass length, larger longissimus muscle area, and greater lean percentage (Simpson et al., 1986; Webb and Simpson, 1986; Simpson and Webb, 1989). In addition, Zhang et al. (1992) reported that the presence of the halothane

9 2354 Kerth et al. Table 4. Least squares means and SEM for diet main effects and a genotype chilling method interaction effect on sensory traits for loin chops Genotype Diet MON NON Trait SEM P > F AC NC SEM AC NC SEM P > F Initial juiciness a b 5.2 c b 5.7 b Sustained juiciness a b 5.2 c b 5.7 b Initial tenderness a Sustained tenderness a 6.1 c 6.5 b 6.5 b 6.6 b Pork flavor a 6.4 c 6.5 c 6.5 c 6.7 b Flavor intensity a b 6.0 c b 6.2 b Overall mouthfeel a 5.7 c 6.0 b 6.0 b 6.2 b a 5 = slightly juicy, tender, pork-like flavor, intense, and characteristic of pork, 6 = moderately juicy, tender, pork-like flavor, intense, and characteristic of pork. b,c Means in a row within an interaction or main effect treatment having the same or no superscript do not differ (P > 0.05). gene accounted for 1 to 10% of the variation in meat quantity and growing traits. Ramsey et al. (1995) found that supplementing 150 IU/kg vitamin E increased ADG did not affect feed efficiency, increased backfat thickness, and numerically increased USDA carcass grade. In contrast, the present study showed that, with the exception of 10th rib fat, neither genotype nor diet affected any growth or carcass trait of commercial pigs. It has long been known that PSE meat is unfavorable in the pork industry. Bray (1966) reported that fresh and cured PSE pork had less desirable palatability, higher shrinkage, undesirable processing characteristics, and excessive amounts of purge compared to normal pork. Briskey et al. (1962) and Bendall et al. (1963) demonstrated that muscles that became PSE usually had a shorter rigor duration, as indicated by a rapid decline in ph postmortem. In the present study we observed that supplementing vitamin E to the finishing diet resulted in a less rapid decline in muscle ph in NON pigs. Noncarrier pigs that were fed either 0 or 300 diets had a lower ph than those fed the 600 diet, which resulted in a higher percentage of loins that were scored PSE. Because of the large economic impact that the PSE condition has on the pork industry (Meeker and Sonka, 1994), much effort has gone into methods to reduce the incidence of PSE pork. Lawrie (1974) concluded that rapid chilling can slow postmortem glycolysis and increase the ultimate muscle ph. A number of methods have been successful in increasing the rate of chilling. Frederick et al. (1993), Meade and Miller (1990), and Owen et al. (1995) reported that hot-fat trimming of pork carcasses increased the rate of temperature decline and reduced the incidence of PSE meat. Milligan (1998) and Springer (1997) reported that rapid chilling ( 32 C for at least 90 min) improved muscle color and purge characteristics, whereas McFarlane and Unruh (1996) reported that rapid chilling improved cooking loss but did not affect color characteristics. The current study parallels previous research indicating that rapid chilling increases the rate of postmortem temperature decline, which resulted in improved loin and ham fresh color and firmness, sensory characteristics, and Meat- Check scores in the ham. The result was a reduction in the incidence of PSE in both the loin and ham of pigs that did not carry a copy of the halothane gene. Dietary supplementation of vitamin E decreased drip loss and improved the color of pork cuts with limited success (Monahan et al., 1990; Asghar et al., 1991; Cannon et al., 1996). Prior studies used only one level of vitamin E in addition to other vitamins and minerals (Ramsey et al., 1995) and therefore it could not be determined whether it was the vitamin E or the other supplements that produced the treatment effect. In this study, however, by varying the level of vitamin E, we determined that supplementing at least 600 IU/kg along with riboflavin, vitamin C, selenium, manganese, magnesium, copper, and zinc successfully reduced the incidence of PSE pork in pigs that are noncarriers of the halothane gene. Many problems, such as PSE meat, are associated with pigs that carry the halothane gene, so it may be expected that technologies to reduce the incidence of PSE would be most effective on pigs that are carriers of the gene. In the present study it was shown that neither vitamin-mineral supplementation nor accelerated chilling had much effect on the meat quality of MON pigs, although accelerated chilling did improve loin juiciness in MON pigs. In contrast, the supplementation of at least 600 IU of vitamin E in the finishing diet of NON pigs drastically reduced quality defects of the muscle. Implications Because of the extensive economic loss and quality deficiencies associated with pale, soft, and exudative pork, the industry is continually looking for methods to improve pork quality. This study showed that although ineffective for pigs carrying the halothane gene, supplementing finishing diets with 600 IU of vitamin E with other vitamins and minerals during the last 36 to 70 d

10 Pork quality 2355 before slaughter can be used in conjunction with accelerated chilling to improve pork quality. Literature Cited AMSA Research Guidelines for Cookery, Sensory Evaluation and Instrumental Tenderness Measurements of Fresh Meat. Am. Meat Sci. Assoc., Chicago, IL. Asghar, A., J. I. Gray, A. M. Booren, E. A. Goma, M. M. Abouzied, E. R. Miller, and D. J. Buckley Effects of supranutritional dietary vitamin E levels on subcellular deposition of α-tocopherol in the muscle and on pork quality. J. Sci. Food Agric. 57: Bendall, J. R., O. Hollund, and J. Wismer-Pedersen Post-mortem changes in the muscles of Landrace pigs. J. Food Sci. 28: Bray, R. W Pork quality definition, characteristics and significance. J. Anim. Sci. 25: Briskey, E. J., R. N. Sayre, and R. G. Cassens Development and application of an apparatus for continuous measurement of muscle extensibility and elasticity before and during rigor mortis. J. Food Sci. 27: Cannon, J. E., J. B. Morgan, G. R. Schmidt, J. D. Tatum, J. N. Sofos, G. C. Smith, R. J. Delmore, and S. N. Williams Growth and fresh meat quality characteristics of pigs supplemented with vitamin E. J. Anim. Sci. 74: Craig, A. M., L. L. Blythe, K. E. Rowe, E. D. Lassen, R. Barrington, and K. C. Walker Variability of α-tocopherol values associated with procurement, storage, and freezing of equine serum and plasma samples. Am. J. Vet. Res. 53: Cross, H. R., R. Moen, and M. S. Stanfield Training and testing of judges for sensory analysis of meat quality. Food Technol. 37: Frederick, T. L., M. F. Miller, D. K. Jones, M. K. Meade, and C. B. Ramsey Hot-fat trimming of carcasses to reduce the incidence of pale, soft and exudative pork. J. Anim. Sci. 71(Suppl. 1):11 (Abstr.). Lawrie, R. A Meat Science. 2nd ed. Pergamon Press, Oxford, U.K. McFarlane, B. J., and J. A. Unruh Effects of blast chilling and postmortem calcium chloride injection on tenderness of pork longissimus muscle. J. Anim. Sci. 74: Meade, M. K., and M. F. Miller The use of rapid chilling to reduce pale, soft and exudative pork from highly stressed market hogs. J. Anim. Sci. 69(Suppl. 1):351 (Abstr.). Meeker, D., and S. Sonka Pork Chain Quality Audit. National Pork Producers Council, Des Moines, IA. Milligan, S. D., C. B. Ramsey, M. F. Miller, C. S. Kaster, and L. D. Thompson Resting of pigs and hot-fat trimming and accelerated chilling of carcasses to improve pork quality. J. Anim. Sci. 76: Monahan, F. J., D. J. Buckley, J. I. Gray, P. A. Morrissey, A. Asghar, T. J. Hanrahan, and P. B. Lynch Effect of dietary vitamin E on the stability of raw and cooked pork. Meat Sci. 27: Monahan, F. J., J. I. Gray, A. Asghar, A. Haug, B. Shi, and D. J. Buckley Effect of dietary lipid and vitamin E supplementation on free radical production and lipid oxidation in porcine muscle microsomal fractions. Food Chem. 46:1 6. NPPC Procedures to Evaluate Market Hogs. 3rd ed. National Pork Producers Council, Des Moines, IA. Ott, L An Introduction to Statistical Methods and Data Analysis. 3rd ed. PWS-Kent Publishing Co., Boston, MA. Owen, B. L., C. B. Ramsey, and M. F. Miller Preslaughter rest and hot-fat trimming to reduce PSE pork. J. Anim. Sci. 73(Suppl. 1):164(Abstr.). Ramsey, C. B., L. L. Hamman, and M. F. Miller Vitamin/ mineral nutritional modulation, stress, and hot-fat trimming effects on quality of pork from pigs monomutant for the PSE gene. J. Anim. Sci. 73(Suppl. 1):160(Abstr.). Simpson, S. P., and A. J. Webb Growth and carcass performance of British Landrace pigs heterozygous at the halothane locus. Anim. Prod. 49: Simpson, S. P., A. J. Webb, and I. Wilmut Performance of British Landrace pigs selected for high and low incidence of halothane sensitivity. 1. Reproduction. Anim. Prod. 43: Springer, M. P Freeze Chilling of Carcasses to Improve Pork Quality. M.S. thesis. Texas Tech Univ., Lubbock. Webb, A. J. and S. D. Simpson Performance of British Landrace pigs selected for high and low incidence of halothane sensitivity. 2. Growth and carcass traits. Anim. Prod. 43: Zhang, W., D. L. Kuhlers, and W. E. Rempel Halothane gene and swine performance. J. Anim. Sci. 70: