J. Anim. Sci. 2004. 82:2264-2268
© 2004 American Society of Animal Science
Breed differences and genetic parameters of myoglobin concentration in porcine longissimus muscle1,2
D. W. Newcom*,
K. J. Stalder*,3,
T. J. Baas*,
R. N. Goodwin
,4,
F. C. Parrish* and
B. R. Wiegand
* Department of Animal Science, Iowa State University, Ames 50011;
and
National Pork Board, Des Moines, IA 50306; and
and
Department of Agriculture, Illinois State University, Normal 61790
 |
Abstract
|
|---|
An evaluation of porcine longissimus myoglobin concentration was conducted to determine breed and gender differences for myoglobin content, estimate genetic parameters for myoglobin concentration, and determine the relationship between myoglobin content and objective measures of muscle color. Data from centrally tested (n = 255), purebred Yorkshire (42), Duroc (61), Hampshire (17), Chester White (28), Berkshire (67), Poland China (28), and Landrace (12) barrows and gilts from the 1999 National Barrow Show Sire Progeny Test were used. Ultimate pH and Hunter L were measured on the 10th-rib face 24 h postmortem. A section of bone-in loin containing the 10th rib was taken to the Iowa State University Meats Laboratory. At 48 h postmortem, Hunter L, CIE L*, a*, and b*, Japanese color score, and water-holding capacity were measured on the face of the 10th-rib loin chop. A slice from the 10th-rib loin section was evaluated for percentage of i.m. fat. The resulting loin chop was used for the determination of soluble myoglobin concentration (mg/g, wet basis). Chester White, Hampshire, and Duroc pigs had the highest (P < 0.05) myoglobin concentration (0.92, 0.95, and 0.85 mg/g, respectively), whereas Landrace had the lowest (0.62 mg/g; P < 0.05). No gender differences were detected for myoglobin concentration. The heritability estimate for soluble myoglobin concentration was 0.27. Residual correlations between soluble myoglobin and CIE L*, a*, b*, Hunter L (24 h), Hunter L (48 h), and Japanese color score were –0.17, 0.23, –0.15, –0.16, –0.13, and 0.13, respectively. These correlations are low but in the desired direction. The residual correlation between soluble myoglobin and intramuscular fat percent was 0.18. Results show that myoglobin concentration has a moderate heritability and could be used in a selection program to make pork loins darker in color.
Key Words: Genetic Parameters • Myoglobin • Pork • Quality
|
Introduction
|
|---|
Pork quality has become a primary focus for producers, researchers, packers, processors, retailers, and ultimately, consumers. This has become especially true for niche producers and pork processors involved in exporting pork. Lean meat color has often been associated with consumer acceptance of fresh meat cuts, and may be the single most important factor consumers use to evaluate pork in the meat case (Faustman and Cassens, 1990
). Some consumer segments prefer pork that is darker in color, particularly the upscale restaurant trade and specialty markets. Additionally, muscle color plays a significant role in pork exports, particularly to Asia (Cravens, 1997; Miller et al., 1999; Vonada et al., 2000). In 2001, total pork exports added nearly $1.5 billion to the U.S. pork chain, with almost $1 billion of that coming from the Asian market (USMEF, 2003). Meeting the demands of export consumers could add substantially to the profitability of both pork processors and producers.
Lean meat color has been evaluated with multiple subjective and objective measures (NPPC, 2000). Most methods have only been indicators of the biologically active component of meat color. Myoglobin (MB) is the oxygen-binding protein in muscle that gives meat its characteristic red color (Garrett and Grisham, 1999). Increasing MB content and thus changing lean pork color could make pork more competitive in domestic and export markets.
For selection to be successful within and among breeds, sufficient additive genetic variation must exist, reliable genetic parameters must be available, and superior individuals must be selected to produce the next generation of progeny. Therefore, the objectives of this study were to determine breed and gender differences for MB content, estimate genetic parameters for MB concentration, and determine the relationship between MB content and objective measures of color in porcine LM.
|
Materials and Methods
|
|---|
Data from centrally tested purebred (n = 255) Yorkshire, Duroc, Hampshire, Chester White, Berkshire, Poland China, and Landrace barrows (n = 124) and gilts (n = 131) from the 1999 National Barrow Show sire progeny test (Goodwin, 2000) were evaluated to determine the genetic parameters for myoglobin content of the LM. Three generation pedigrees were obtained for all animals and pigs were determined to be free of the Halothane gene by DNA test (Fujii et al., 1991). Molecular tests for Rendement Napole were not available at this time. The distribution of records is shown in Table 1.
Pigs were delivered to the Northeast Iowa Swine Testing Station in New Hampton at approximately 8 wk of age and were penned by sire group in a solid-concrete-floored, open-front building and given 1.4 m2 of pen space per pig. Pens were placed on test when the pen averaged 31.7 kg and pigs were provided ad libitum access to feed and water. Diets provided met or exceeded NRC (1998) nutrient requirements. Animals were weighed weekly and removed from test when they reached an approximate end weight of 108.9 kg. Pigs were then shipped to Hormel Foods/Quality Pork Processors in Austin, MN, and slaughtered after an overnight rest period.
Following harvest and a 24-h chill, ultimate pH was measured on the 10th-rib face of the LM using a pH star probe (SFK Ltd., Hvidovre, Denmark). Hunter L (L24) was measured on the 10th-rib face of the loin using a Minolta CR-310 (Minolta Camera Co., Ltd., Tokyo, Japan) (a measure of light reflectance where lower value indicates darker and more desirable color) with a 50-mm-diameter aperture, D65 illuminant, and calibrated to the white calibration plate. A section of bone-in loin containing the 10th rib was removed from the carcass and transported to the Iowa State University Meat Laboratory in Ames. At 48 h postmortem, Hunter L score (L48), was measured using the Minolta 310-CR on the 10th-rib loin face. The CIE L* (a measure of the white/black color spectrum where lower values indicate darker and more desirable color), a* (larger positive values indicate more red color), and b* (measure of the yellow/blue color spectrum) values (HunterLab, 1983) were obtained with a Hunter LabScan colorimeter (Hunter Laboratory, Inc., Reston, VA), fitted with a 25-mm aperture, A illuminant, and calibrated to a white standard tile. Japanese color score (1 to 6) (Nakai, 1991) and water-holding capacity (WHC), by the filter paper method of Kauffman et al. (1986), were measured on the face of the 10th-rib sample. A 3.2-mm slice from the 10th-rib chop was used for i.m. fat determination (Bligh and Dyer, 1959). Soluble MB content (SM) was determined using the method of Hunt (1980) on the resulting loin chop.
Least squares means were determined using a mixed linear model (PROC MIXED; SAS Inst., Inc., Cary, NC) that included fixed effects of breed, gender, and harvest date, and random effects of sire and dam within breed. Means were compared using pairwise t-tests and determined to be different at P < 0.05. Heritability estimates were calculated as four times sire variance divided by total variance (4
s2/t2; Falconer and MacKay, 1996) from a restricted maximum likelihood algorithm in the PROC MIXED analysis. Standard errors were estimated by the Delta Method of Lynch and Walsh (1998). Residual correlation coefficients between the traits were calculated using a fixed linear model with fixed effects of breed and harvest date in the multivariate ANOVA in PROC GLM (SAS Inst. Inc.).
|
Results and Discussion
|
|---|
Least squares means by breed are reported in Table 2. Significant breed differences for longissimus SM occurred in this study. The Hampshire and Chester White breeds had higher (P < 0.05) LM SM when compared with Berkshire, Landrace, Poland China, and Yorkshire breeds, but were not different from Durocs. This agrees with the result of Lindahl et al. (2001), who found Hampshires had higher pigment content when compared with Swedish Yorkshires and Landrace pigs. Additionally, longissimus SM was higher (P < 0.05) for the Duroc pigs when compared with the Landrace and Yorkshire breeds. The SM of Berkshire and Poland China pigs was higher (P < 0.05) compared with the Landrace breed. The results from the current study differ from previous results reported by Allen et al. (1966), where Yorkshires had higher levels of MB than did Durocs. The differences between the present investigation and those previously reported are likely due to selection for decreased backfat thickness to increase percentage of lean meat since the previous study was conducted.
View this table:
[in this window]
[in a new window]
|
Table 2. Breed and gender least squares means (SE) for muscle quality traits from the 1999 National Barrow Show sire progeny test
|
|
Breed differences in SM were closely mirrored by the breed differences in some objective color measures, particularly in identifying breeds with LM that was paler than other breeds. Results for CIE L* showed that Landrace pigs had higher (P < 0.05) values (paler color) compared with the Berkshire, Chester White, Duroc, and Hampshire breeds (Table 2
). For the measure of the red/green color spectrum, a*, breed differences also occurred. Hampshire pigs had higher (P < 0.05) a* values than the other six breeds involved in this study, which is similar to the findings of Lindahl et al. (2001). Objective color results closely follow the myoglobin results. Miller et al. (2000) reported Hampshire pigs that were carriers of the Napole gene showed no difference in L* or a* values compared with homozygous recessive animals, but were different from Yorkshires. Because Napole is known to affect muscle quality, pH, and WHC in particular (Hamilton et al., 2000; Moeller et al., 2003), and can be found primarily in Hampshire pigs (Miller et al., 2000), the results reported for Hampshire pigs in this study could be attributed to, at least partially, the unknown incidence of the Napole gene. Similarly, Duroc pigs had higher (P < 0.05) a* values compared with Berkshire, Landrace, Poland China, and Yorkshire pigs. There were no breed differences detected for b*. This finding is not in agreement with the findings of Lindahl et al. (2001) who found Hampshire pigs had higher b* values.
Breed differences (P < 0.05) for Hunter L value measured 24 (L24) and 48 (L48) h postmortem did occur in this study (Table 2). Landrace and Yorkshire LM had higher (P < 0.05) L24 (paler) values compared with the other five breeds in this study. These findings are similar to those reported by Berger et al. (1994). Ball et al. (1996) also found Landrace pigs had the palest lean meat color when compared with Duroc, Hampshire, and Yorkshire pigs. Berkshire pigs had lower (P < 0.05; darker) L24 values when compared with Chester White, Duroc, Landrace, Yorkshire, and Poland China pigs. These findings are consistent with previous research (Berger et al., 1994; Goodwin, 1994). Breed differences for L48 were also observed (Table 2). Berkshire LM had the lowest L48 values compared with all other breeds, but was lower (P < 0.05) than only the Duroc, Landrace, Poland China, and Yorkshire breeds. Similarly, Chester White and Duroc LM had lower L48 values when compared with the Yorkshires (Table 2). Breed differences for Japanese color score, a subjective evaluation of muscle color, closely mirror the results of the 24-h Hunter L evaluation (Table 2).
Hampshires had the lowest pH value and highest WHC values, but were not different (P < 0.05) from Landrace, Poland China, or Yorkshire pigs for pH, and only different (P < 0.05) from Berkshires and Chester White pigs for WHC (Table 2). Berger et al. (1994) reported Hampshire pigs had a lower (P < 0.05) pH than any other breed, which could be attributed to greater power to detect differences than the current study or a higher incidence of Napole. Miller et al. (2000) reported Napole carriers had a lower pH than homozygous recessive Hampshires and Yorkshires. Duroc and Chester White pigs had the highest (P < 0.05) levels of i.m. fat percentage, which agrees with the finding of Berger et al. (1994). Landrace and Yorkshire pigs had the lowest (P < 0.05) levels of i.m. fat percentage, but were not different (P < 0.05) from Hampshires or Poland Chinas. Ball et al. (1996) reported Duroc pigs had the highest level of i.m. fat percentage, but were not different from Hampshires or Yorkshires. These results are different than those found in the current study, and are likely due to differences in the selection goals that exist in the Canadian breeding program.
Least squares means by gender are shown in Table 2. Barrows had higher (P < 0.05) b* values than gilts. Gilts had lower (P < 0.05) L48 values than barrows. Hamilton et al. (2000) reported no gender differences for CIE L*, a*, and b*. Barrows had 0.66 greater (P < 0.05) percentage of i.m. fat in the LM than did gilts, which closely follows previously published results (Goodwin, 1994; Hamilton et al., 2000). No detectable gender differences were observed for SM, L*, a*, pH, L24, WHC, or Japanese color score.
Heritability estimates are shown in Table 3. The heritability estimate for soluble MB concentration was 0.27 (± 0.09), and was lower than that reported by Allen et al. (1966). Heritability estimates for other measures of lean meat color were higher than that of MB concentration. The CIE L*, a*, and b* were highly heritable (0.98, 0.52, and 0.94, respectively). Sellier (1998) reported an average heritability of 0.28 for L* from 29 published estimates, with a range of 0.15 to 0.57, which is lower than the estimate found in this study. The high heritability estimates could be due to the current study design, where sources of environmental variation were limited. All pigs were tested in the same environment, harvested at the same facility with large numbers per contemporary group, and had the same people measuring carcasses within each group. Producers were also permitted to select their pigs for the test, which may not represent a random sample of their herd or breed for a given trait. This could potentially produce a greater decrease in phenotypic variation than additive genetic variation, thereby inflating the heritability estimates. Hunter L taken at 24 and 48 h were also highly heritable, 0.56 and 0.62, respectively. Water-holding capacity was moderately heritable at 0.32. This is higher than the average (0.15), but within the range of values (0.01 to 0.43) reported by Sellier (1998). Heritability estimates for pH and i.m. fat percentage were greater than 1, and were likely due to the low numbers of sires and large sire variance, and are not reported.
View this table:
[in this window]
[in a new window]
|
Table 3. Heritability estimates and standard errors for muscle quality traits from the 1999 National Barrow Show sire progeny test
|
|
Residual correlation coefficients that were calculated using a fixed linear model with fixed effects of breed and harvest date are shown in Table 4. Residual correlations were calculated to examine the relationship among the meat quality traits after accounting for the known sources of variation from the analysis model. The absolute value of the residual correlations between soluble myoglobin concentration and other muscle quality indicator traits were 0.23 or less (Table 4). The residual correlation between SM and CIE a* was 0.23. The correlation is low, but it is a positive association that demonstrates that increasing myoglobin content should increase CIE a* values (more red coloring of pork). The residual correlation between SM and CIE L* was –0.17. The negative relationship between SM and CIE L* is desirable as increasing SM would decrease CIE L* and be indicative of pork muscle that would be of a darker color than pork with lower SM values. The residual correlation between SM and Japanese color score was 0.13. Although this number is low, it is positive, indicating that as SM values increase, Japanese color scores also increase (higher scores indicate darker color). Absolute values of the residual correlations between other objective and subjective measures of color were between 0.23 and 0.87, with the majority of the correlations having an absolute value above 0.58.
View this table:
[in this window]
[in a new window]
|
Table 4. Residual correlation coefficients between muscle quality traits measured in the pork longissimus from the 1999 National Barrow Show sire progeny test
|
|
|
Implications
|
|---|
With the growing importance of export markets, seedstock producers, breeding stock companies, commercial pork producers, packers, and processors must continue to improve fresh pork color and ultimately, fresh pork quality. Myoglobin, the muscle protein that gives meat its red color, could become instrumental in improving lean color through identification of breeds superior for myoglobin concentration and selecting superior individuals as breeding animals. Residual correlations between myoglobin content and other indicators of fresh pork quality are in a favorable direction, indicating selection for increased myoglobin concentration also should improve other meat quality traits. By selecting superior breeds and individuals, more fresh pork should qualify for export marketing, whereby increasing the value of the entire pork production chain.
|
Footnotes
|
|---|
1 This journal paper of the Iowa Agric. and Home Econ. Exp. Stn., Ames 50011, Project No. 3614, was supported by Hatch Act and State of Iowa funds in addition to support from the National Pork Board. 
2 The authors wish to acknowledge the support of Hormel Foods Corp., Austin, MN, and the Northeast Iowa Swine Testing Station, New Hampton, for their efforts contributing to the success of this study.
4 Current address: 4004 Phoenix St., Ames, IA 50010.
3 Correspondence: 109 Kildee Hall (phone: 515-294-4683; fax: 515-294-5698; e-mail: stalder{at}iastate.edu).
Received for publication September 29, 2003.
Accepted for publication April 12, 2004.
|
Literature Cited
|
|---|
Allen, E., J. C. Forrest, A. B. Chapman, N. First, R. W. Bray, and E. J. Briskey. 1966. Phenotypic and genetic associations between porcine muscle properties. J. Anim. Sci. 25:962–966.
Ball, R. O., J. P. Gibson, C. A. Aker, K. Nadarajah, B. E. Uttaro, and A. Fortin. 1996. Differences among breeds, breed origins, and gender for growth, carcass composition, and pork quality. Pages 12–20 in Ontario Pork Carcass Appraisal Project Symp. C. A. Aker and R. O. Ball, ed. Ontario Swine Improv. Inc. Guelph, Ontario, Canada.
Berger, P. J., L. L. Christian, C. F. Louis, and J. R. Mickelson. 1994. Estimation of genetic parameters for growth, muscle quality, and nutritional content of meat products for centrally tested purebred market hogs. Pages 51–63 in Research Investment Report 1994. Natl. Pork Prod. Counc., Des Moines, IA.
Bligh, E. G., and W. J. Dyer. 1959. A rapid method for total lipid extraction and purification. Can. J. Biochem Physiol. 3:911–917.
Cravens, J. W. 1997. The role of pork quality in export marketing. Pages 17–24 in Pork Quality Summit. Natl. Pork Prod. Counc. Des Moines, IA.
Falconer, D. S., and T. F. C. MacKay. 1996. Introduction to Quantitative Genetics. 4th ed. Longman, New York.
Faustman, C., and R. G. Cassens. 1990. The biochemical basis for discoloration in fresh meat: A review. J. Muscle Foods. 1:217–243.
Fujii, J., K. Otsu, F. Zorzato, S. De Leon, V. K. Khanna, J. E. Weiler, P. J. O’Brien, and D. H. MacLennan. 1991. Identification of a mutation in porcine ryanodine receptor associated with malignant hyperthermia. Science 253:448–451.[Abstract/Free Full Text]
Garrett, R. H., and C. M. Grisham. 1999. Biochemistry. 2nd ed. Saunders College Publishing, Fort Worth, TX.
Goodwin, R. 2000. From hog show to meat case. Natl. Hog Farmer 8:S3–S5.
Goodwin, R. N. 1994. Genetic parameters of pork quality traits. Ph.D. Diss. Iowa State Univ., Ames
Hamilton, D. N., M. Ellis, K. D. Miller, F. K. McKeith, and D. F. Parrett. 2000. The effect of the Halothane and Rendement Napole genes on carcass and meat quality characteristics of pigs. J. Anim. Sci. 78:2862–2867.[Abstract/Free Full Text]
Hunt, M. C. 1980. Meat color measurements. Proc. Recipr. Meat Conf. 33:41.
HunterLab. 1983. The science and Technology of Appearance Measurement. Hunter Associates Laboratory, Inc., Reston, VA.
Kauffman, R. G., G. Eikelenboom, P. G. van der Wal, B. Engel, and M. Zaar. 1986. A comparison of methods to estimate water-holding capacity in post-rigor porcine muscle. Meat Sci. 18:307–322.
Lindahl, G., K. Lundström, and E. Tornberg. 2001. Contribution of pigment content, myoglobin forms and internal reflectance to the colour of pork loin and ham from pure breed pigs. Meat Sci. 59:141–151.
Lynch, M., and B. Walsh. 1998. Genetics and Analysis of Quantitative Traits. Sinauer Associates, Inc. Sunderland, MA.
Miller, K. D., M. Ellis, F. K. McKeith, B. S. Bidner, and D. J. Meisinger. 2000. Frequency of the Rendement Napole RN–allele in a population of American Hampshire pigs. J. Anim. Sci. 78:1811–1815.[Abstract/Free Full Text]
Miller, R. K., S. J. Moeller, R. N. Goodwin, and G. Davis. 1999. Consistency in meat quality. Natl. Pork Prod. Counc. Quality Lean Growth Modeling Symposium II. Des Moines, IA. November 16–17.
Moeller, S. J., T. J. Baas, T. D. Leeds, R. S. Emnett, and K. M. Irvin. 2003. Rendement Napole gene effects and a comparison of glycolytic potential and DNA genotyping for classification of Rendement Napole status in Hampshire-sired pigs. J. Anim. Sci. 81:402–410.[Abstract/Free Full Text]
Nakai, H. 1991. Meat color evaluation: The evaluation of beef color with standard models. Pages 175–198 in Proc. Electronic Evaluation of Meat in Support of Value-Based Marketing Symp. M. E. D. Judge, ed. Purdue Univ., West Lafayette, IN.
NPPC. 2000. Pork Composition and Quality Assessment Procedures. E. P. Berg, ed. Natl. Pork Prod. Counc., Des Moines, IA.
NRC. 1998. Nutrient Requirements of Swine. 10th ed. Natl. Acad. Press, Washington, DC.
Sellier, P. 1998. Genetics of meat and carcass traits. Pages 463–510 in Genetics of the Pig. M. F. Rothschild and A. Ruvinsky, ed. CAB International, Wallingford, Oxon, U.K.
USMEF. 2003. U. S. Meat Export Federation. Available: http://www.usmef.org. Accessed Aug. 10, 2003.
Vonada, M. L., B. S. Bidner, K. E. Belk, F. K. McKeith, W. R. Lloyd, M. E. O’Connor, and G. C. Smith. 2000. Quantification of pork belly and Boston butt quality attribute preferences of South Korean customers. J. Anim. Sci. 78:2608–2614.[Abstract/Free Full Text]
This article has been cited by other articles:
|
|
|
|
 
S. Zhang, T. J. Knight, K. J. Stalder, R. N. Goodwin, S. M. Lonergan, and D. C. Beitz
Effects of breed, sex, and halothane genotype on fatty acid composition of pork longissimus muscle
J Anim Sci,
March 1, 2007;
85(3):
583 - 591.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
D. W. Newcom, T. J. Baas, C. R. Schwab, and K. J. Stalder
Genetic and phenotypic relationships between individual subcutaneous backfat layers and percentage of longissimus intramuscular fat in Duroc swine
J Anim Sci,
February 1, 2005;
83(2):
316 - 323.
[Abstract]
[Full Text]
[PDF]
|
|
|
Top
Abstract
Introduction
