J. Anim. Sci. 2003. 81:1895-1899
© 2003 American Society of Animal Science
Evaluation of Duroc- vs. Pietrain-sired pigs for carcass and meat quality measures1
D. B. Edwards,
R. O. Bates2 and
W. N. Osburn
Department of Animal Science, Michigan State University, East Lansing 48824
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Abstract
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Crossbred progeny sired by either Duroc or Pietrain boars, normal for the ryanodine receptor gene, were evaluated for carcass composition and meat quality. Boars from each breed were mated to Yorkshire or F1 Yorkshire-Landrace females. A total of 162 offspring was evaluated for carcass and meat quality traits at a common age (approximately 26 wk of age). Duroc-sired progeny had heavier (108.0 vs. 103.0 kg, P < 0.001) and longer carcasses (86.9 vs. 84.8 cm, P < 0.01), whereas Pietrain-sired pigs had less backfat at the first rib (44.6 vs. 47.7 mm, P < 0.01), last lumbar vertebrae (20.9 vs. 23.0 mm, P < 0.05), and 10th rib (23.0 vs. 25.5 mm, P < 0.01). No difference between Pietrain and Duroc progeny was detected for fat depth at the last rib (27.8 vs. 28.8 mm, respectively). Pietrain progeny had a higher percentage of lean at slaughter (52.6 vs. 50.7, P < 0.05) and higher dressing percentage (74.0 vs. 73.1, P < 0.01). Primal cut weights were collected with Pietrain progeny having a greater percentage of carcass as ham (23.0 vs. 22.4, P < 0.01) and loin (21.6 vs. 21.2, P < 0.05), whereas Duroc progeny had a higher percentage of belly weight (12.0 vs. 11.7, P < 0.05). Percentages of Boston butt (8.8 vs. 9.0) and picnic shoulder (9.9 vs. 9.9) were similar for Duroc vs. Pietrain progeny. Total weight of these five primal cuts, as a percentage of carcass weight, was higher for Pietrain progeny (75.2 vs. 74.3, P < 0.01). With heavier carcass weight, Duroc progeny had greater primal cut weights as a function of age. Subjective meat quality scores for color, marbling, and firmness (1 to 5 scale) were more favorable for Duroc-sired progeny. Furthermore, chops from Duroc progeny had higher 24-h pH (5.53 vs. 5.48, P < 0.001) and Minolta a* (17.33 vs. 17.04, P < 0.05) with less percentage drip loss (2.88 vs. 3.80, P < 0.001). No differences were detected between Duroc- and Pietrain-sired progeny for Minolta L* (54.77 vs. 55.37) or b* (7.58 vs. 7.58) objective color scores, percentage cooking loss (28.63 vs. 29.23), or Warner-Bratzler shear force (6.94 vs. 7.11 kg). Both sire breeds have beneficial traits that can be utilized in commercial pork production and merit further study.
Key Words: Breeds • Carcass Composition • Meat Quality • Pigs
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Introduction
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Maintaining acceptable meat quality in the pork industry is an important issue. Selection for growth and leanness while maintaining meat quality is a challenge because of the decrease in meat quality with leaner, faster-growing pigs at heavier slaughter weights (Cisneros et al., 1996
). Different breeds and lines have a predetermined propensity toward excellence in certain areas of carcass composition and meat quality (McLaren et al., 1987; Ellis et al., 1996; Moeller et al., 1998).
Novel populations may contain untapped potential for improvement in composition and meat quality traits. The Pietrain breed is a population that has been used in Europe, but has not been used extensively within the United States. Differences have been reported in meat quality measures of pH at 24 h postslaughter, marbling, and water-holding capacity with Duroc-sired progeny having advantages over Pietrain-sired progeny in these traits (Affentranger et al., 1996; Ellis et al., 1996; Garcia-Macias et al., 1996). All of these studies have included Pietrain animals that contained at least one copy of the mutant ryanodine receptor gene, which has detrimental effects on pork quality (Sellier, 1998). Pietrain populations are now available that are homozygous normal at this locus. Pietrain- and Duroc-sired progeny, normal for the ryanodine receptor gene, were raised to a common age and evaluated for composition and meat quality traits at weights typical of U.S. production systems.
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Materials and Methods
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Data Collection
Sires from Duroc and Pietrain populations were used to produce 413 crossbred progeny for this study, born between October 24, 1997 and May 7, 1999. All animals used were determined to be homozygous normal for the ryanodine receptor gene from pedigree information. Duroc sires ranked within the top 40% of the breed for Terminal Sire Index (an economic index based on growth and body composition) as reported by the National Swine Registry. An effort was made to select Duroc boars from unrelated families within the breed. Pietrain boars were from a closed herd whose ancestors were imported to the United States from Germany. This herd is homozygous normal at the ryanodine receptor locus. An attempt was made to sample each of nine sires available at each time of mating. A total of 23 litters from 23 Duroc sires and 23 litters from 16 Pietrain sires were evaluated.
Dams for this study were housed at the Michigan State University Swine Teaching and Research Farm. Yorkshire and F1 Yorkshire-Landrace females within parity and breed classification subclass were randomly assigned to be single sire mated using AI to either a Duroc or Pietrain boar. Four farrowing groups were used to obtain pigs. Pigs were individually identified at birth.
At weaning (mean of 24.7 d of age), pigs were sorted into sire breed, gender, and weight subgroups and randomly assigned to nursery pens. Pigs were provided diets on an ad libitum basis that met or exceeded nutritional requirements (NRC, 1998) for each production stage. At 10 wk of age, pigs (307 total) within two standard deviations of the mean weight within replication were taken to a grow-finish facility and randomly assigned to pens in groups of four sorted by sire breed, gender, and weight. No difference in weight at 10 wk of age was observed between Duroc- and Pietrain-sired pigs (31.43 vs. 30.95 kg). At the end of the grow-finish period (approximately 26 wk of age), pigs near the mean weight within gender of each litter (162 total, Table 1) were slaughtered and carcass measurements and meat quality assessment completed.
Pigs were fasted overnight and weighed prior to shipment (approximately 150 km). Pigs (n = 130 over seven slaughter dates) were slaughtered at a small, federally inspected plant in western Michigan. The remaining animals (n = 32 over 4 slaughter dates) were slaughtered at the Michigan State University Meat Laboratory. Carcass weights were obtained prior to chilling. Carcasses were allowed to chill approximately 24 h, and measurements were taken from one side. Data collected included carcass length and midline backfat at the first rib, last rib, and last lumbar vertebrae. During carcass dissection into primal cuts, off-midline backfat at the 10th rib (BF10) and loin muscle area (LMA) were measured. Dressing percentage and fat-free lean percentage (FFL%) (NPPC, 2000) were calculated from live weight and carcass measures of weight, BF10, and LMA.
Primal cut weights of the ham, closely trimmed loin, Boston butt, picnic shoulder, and belly were obtained from one side. Percentages of each primal cut vs. carcass weight were calculated. The percentage of carcass weight in these five primal cuts was calculated. A ham-loin weight and percentage were also calculated.
A loin section (10th to last rib) from each carcass was harvested, weighed, placed in plastic bags and into an insulated cooler, packed with ice, and returned to the Michigan State University Meat Laboratory for fresh meat quality analysis. Immediately upon return, a small piece of each section was retained and frozen at -80°C for 24-h pH analysis by the iodoacetate method (Bendall, 1973). Each section was cut into 2.54-cm boneless chops. Two chops were allowed to bloom for 10 min and subjective scores (1 to 5) were assessed for each chop for color, marbling, and firmness (NPPC, 1991). Color scores ranged from 1 (pale pinkish-gray) to 5 (dark purplish-red). Marbling scores were 1 (devoid to practically devoid of marbling, <2% intramuscular lipid) to 5 (moderately abundant, >8% intramuscular lipid). Firmness scores were 1 (very soft and watery) to 5 (very firm and dry). Light reflectance scores for L*, a*, and b* were obtained using a Minolta CR-310 colorimeter (Ramsey, NJ) with a D65 light source and a two-degree standard observer. Chops were then weighed and hung in sealed plastic bags for 24 h at 4°C, and then weighed again for drip loss measurement. Two additional chops were vacuum packaged and frozen for later analysis of cooking loss and Warner-Bratzler (W-B) shear force. For cook loss measurements, each chop was thawed, weighed, cooked to 71°C internal temperature on Farberware open hearth electric broilers, cooled to room temperature, and weighed again. From these chops, six cores (three cores from each chop) were taken parallel to the muscle fiber direction and W-B shear force measured.
Data Analysis
Least squares means by breed of sire for carcass weight, length, first rib fat, last rib fat, last lumbar fat, BF10, LMA, FFL%, dressing percent, and primal cut weights were estimated using the following model:
where Yijklm = record on the mth subject within the ith breed of sire, jth breed of dam, kth gender, and lth slaughter group, µ = overall mean of trait, bosi = fixed effect of sire breed i (Duroc or Pietrain), bodj = fixed effect of dam breed j (Yorkshire or F1 Yorkshire-Landrace), sexk = fixed effect of animal’s gender k (barrow or gilt), slggrpl = fixed effect of slaughter group l (1, 2, 3, 4, or 5), bos x sexjk = interaction of fixed effects of sire breed j and gender k of animal, gijklm = random effect of animal m ~ N(0,
), bage x Ageijklm = standardized covariate of age of animal, eijklm = random error ~N(0,
).
An interaction term of breed of sire x gender of animal was included since it was determined to contribute to the model through the use of an F-test. The (co)variance matrix for the animal effect was , where A was the numerator relationship matrix among animals. It included all animals in pedigrees for paternal and maternal grandsires and granddams of boars that sired progeny and sires and dams of females that farrowed litters. A standardized covariate of age of animal minus mean age (193.8 d) and divided by standard deviation of age (3.39 d) was used in the model for all of these traits to account for age differences between animals at slaughter.
Least squares means for meat quality traits, including subjective color, marbling, and firmness scores, Minolta L*, a*, and b* readings, 24-h pH, drip loss, cook loss, and shear force were estimated using the same model as for carcass measurements. An additional term of sample nested within animal was included in the model to account for within pig variation from sample to sample. Shear force measurements had six samples per pig, whereas other meat quality measures had two samples per pig.
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Results and Discussion
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Carcass Traits
Least squares means by sire breed for carcass measurement response variables are listed in Table 2. Duroc progeny were longer (P < 0.01), had more midline backfat at the first rib (P < 0.01), and more off-midline 10th-rib backfat (P < 0.01). Midline backfat at the last lumbar was also greater for Duroc progeny (P < 0.05). These results are in agreement with findings by Kanis et al. (1990), who reported Duroc pigs had more backfat than Pietrain pigs at 60 kg (10.5 vs. 8.7 mm, respectively), at 100 kg (17.5 vs. 12.3 mm, respectively), and at 140 kg (24.4 vs. 17.4 mm, respectively). Similar results were also reported by Ellis et al. (1996), with Duroc-sired progeny having fatter carcasses, measured at a right angle to the line at which the maximal width of the loin muscle was recorded, than progeny of a line that contained Pietrain from pigs slaughtered at 80, 100, or 120 kg (mean fat depths of 15.6 vs. 14.0 mm, respectively). Garcia-Macias et al. (1996) also reported more backfat, measured between the third and fourth last ribs and averaged across pigs slaughtered at 90 and 120 kg, for Duroc vs. Pietrain progeny (19.84 vs. 17.16 mm, respectively). Pietrain progeny had more loin muscle area (P < 0.01), similar to results from Ellis et al. (1996) of 40.7 vs. 39.0 cm2 and Garcia-Macias et al. (1996) of 40.51 vs. 36.77 cm2. Furthermore, Pietrain-sired pigs had a higher dressing percentage (P < 0.01), which differed from results reported by Garcia-Macias et al. (1996), in which no difference was detected (81.18% for Pietrain progeny vs. 81.69% for Duroc progeny). Fat-free lean percentage was also greater for Pietrain progeny (P < 0.001), similar to Kanis et al. (1990), who also reported Pietrain influenced pigs had a higher fat-free lean percentage than Duroc influenced pigs (56.1% vs. 52.7% at 100 kg and 52.2% vs. 50.4% at 140 kg). No significant difference between Duroc and Pietrain-sired progeny was detected for midline backfat at the last rib. This differed from Garcia-Macias et al. (1996), who reported Duroc-sired progeny had 3.07 mm more fat at the last rib than Pietrain-sired progeny.
Table 3 contains least squares means by sire breed for primal cut response variables. Each of the primal cuts was reported as the weight from one side of the carcass. Percentage calculations were obtained by doubling primal cut weight and taking it as a percentage of hot carcass weight. Duroc-sired progeny had a heavier (P < 0.001) carcass, which led to greater weights of primal cuts. However, as a percentage of carcass weight, Pietrain-sired progeny had larger hams (P < 0.01), similar to that reported by Affentranger et al. (1996) (20.3 vs. 18.6%), but Garcia-Macias et al. (1996) reported no ham percentage difference between Duroc and Pietrain progeny. Pietrain progeny in this study had a greater loin percentage (P < 0.05), which differed from results of Garcia-Macias et al. (1996), in which both groups had similar loin percentages. Therefore, Pietrain progeny also had a greater ham-loin percentage (P < 0.001) in this study. Additionally, percentage of five primal cuts was higher for Pietrain progeny compared with Duroc progeny (P < 0.01). Duroc-sired progeny had a greater percentage of carcass weight in the belly (P < 0.05), which agreed with Affentranger et al. (1996), who reported Duroc pigs had 1.1% more belly weight as a percentage of carcass weight. However, this does not agree with Garcia-Macias et al. (1996), who reported larger bellies for Pietrain-sired animals (93.1 g/kg vs. 99.1 g/kg). No significant differences were detected in Boston butt or picnic shoulder percentages. These results were similar to Garcia-Macias et al. (1996), but this conflicts with Affentranger et al. (1996), who reported Pietrain progeny to have a greater percentage of shoulder (11.5 vs. 11.2%).
Meat Quality Traits
Least squares means for meat quality traits by sire breed are listed in Table 4. Subjective color scores were higher for Duroc progeny (P < 0.05). This conflicts with earlier studies (Ellis et al. 1996; Garcia-Macias et al., 1996) that reported no differences in subjective color scores between Duroc- and Pietrain-influenced pigs. Objective Minolta L* and b* values were not different between chops from Duroc- and Pietrain-sired pigs, which agrees with results of Garcia-Macias et al. (1996). Minolta a* values were higher (P < 0.05) for chops from Duroc progeny, which agreed with the subjective color scores. Chops from Duroc-sired progeny had a higher marbling score (P < 0.001), similar to results reported by Ellis et al. (1996). Chops from Duroc progeny had higher firmness scores (P < 0.001). In addition, chops from Duroc progeny had higher 24-h pH compared with chops from Pietrain progeny (P < 0.001). These results agreed with Affentranger et al. (1996) and Garcia-Macias et al. (1996), who reported that chops from Duroc-sired pigs had 0.28 and 0.09 higher pH, respectively, compared with chops from Pietrain-sired pigs. Drip loss was lower for Duroc-sired progeny (P < 0.001). This agreed with Affentranger et al. (1996), who reported a difference of 16.9 µL less water lost in 120 s in a drip-loss test for chops from Duroc-influenced pigs vs. chops from Pietrain-influenced pigs. No significant differences were detected for cooking loss or for W-B shear force. This differs from Ellis et al. (1996), who reported lower W-B shear force for Duroc progeny (5.35 kg) compared with Pietrain progeny (5.67 kg).
The results observed in this study must be seen in a different light than those in the previous studies of Pietrain animals. These previous studies used animals with at least one copy of the mutant ryanodine receptor gene, which has detrimental effects on pork quality (Sellier, 1998). The animals used in this study were homozygous normal at this locus.
Differences were detected between progeny sired by either Duroc or Pietrain boars grown to a similar age. Pietrain-sired progeny had less backfat and more FFL%. Duroc progeny had longer carcasses that were heavier, which led to heavier primal cut weights. Ham-loin percentage was greater for Pietrain-sired animals. Subjective scores for color, marbling, and firmness showed that loin chops from Duroc progeny were darker, more marbled, and firmer. In addition, Duroc-sired progeny had higher 24-h pH and a lower percentage of drip loss. No differences were detected in shear force. Both Duroc and Pietrain populations merit further study into the genetic control of these carcass composition and meat quality traits.
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Implications
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Proper characterization of breeds for carcass and meat quality traits is essential to the choice of terminal sire breeds within pork production and marketing systems. Although carcass traits and meat quality are important, other traits, such as growth and feed efficiency, must also be considered. Traits from Duroc and Pietrain breeds demonstrate genetic differences that could be useful in pork production systems. Different segmented pork markets or pork chains require different product specifications; Duroc- and Pietrain-sired animals can meet many of these needs and be competitive within the pork industry.
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Footnotes
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1 The authors acknowledge the technical assistance of the laboratory of M. Doumit in collecting pH measurements. This project was funded in part by the Michigan Agric. Exp. Stn., Michigan State University, East Lansing, MI and the National Swine Registry, West Lafayette, IN. 
2 Correspondence: 1205 Anthony Hall (phone: 517-432-1387; fax: 517-432-9168; E-mail: batesr{at}msu.edu).
Received for publication November 28, 2001.
Accepted for publication April 11, 2003.
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Abstract
Introduction
