Journal of Animal Science and Technology
Korean Society of Animal Sciences and Technology
RESEARCH ARTICLE

Effects of the slaughter weight of non-lean finishing pigs on their carcass characteristics and meat quality

Sang-Hyon Oh1https://orcid.org/0000-0002-9696-9638, Chul Young Lee1https://orcid.org/0000-0002-4735-1268, Dong-Heon Song2https://orcid.org/0000-0002-4670-3321, Hyun-Wook Kim2https://orcid.org/0000-0002-4397-9664, Sang Keun Jin1https://orcid.org/0000-0002-8983-5607, Young-Min Song1,*https://orcid.org/0000-0002-4190-2997
1Department of Animal Resources Technology, Gyeongsang National University, Jinju 52725, Korea
2Animal Science and Biotechnology, Gyeongsang National University, Jinju 52725, Korea
*Corresponding author: Young-Min Song, Departments of Animal Resources Technology, Gyeongsang National University, Jinju 52725, Korea. Tel: +82-55-751-3282, E-mail: pigsong@gnu.ac.kr

© Copyright 2022 Korean Society of Animal Science and Technology. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: Nov 30, 2021; Revised: Feb 04, 2022; Accepted: Feb 28, 2022

Published Online: Mar 31, 2022

Abstract

The present study aimed to assess the feasibility of increasing the slaughter weight (SW) of non-lean finishing pigs to improve their meat quality. A total of 36 (Landrace × Yorkshire) × Duroc gilts and barrows were slaughtered at 115 (Av), 125 (Hi), or 135 (XHi) kg, followed by physicochemical analyses and sensory evaluation on their longissimus dorsi (LD) and Semimembranosus (SM) muscles. Backfat thickness was greater (p < 0.05) for the XHi (31.2 mm) and Hi (29.3 mm) groups than for Av (25.0 mm). Dressing percentage and yield of the belly per whole carcass were also slightly greater for XHi and Hi vs. Av. The intramuscular fat (IMF) content of SM was greater for XHi (2.64%) than for Av (1.83%) and Hi (2.04%) and also was correlated with SW (r = 0.55). The pH value, lightness, redness, drip loss, shear force, and moisture and protein contents of LD and SM, as well as IMF content of LD, were unaffected by SW. Percentages of 14:0, 16:0, and total saturated fatty acids (FA) were less for Hi and XHi vs. Av in SM, those of total unsaturated FA, 18:2, 20:4, and n-6 being opposite; FA composition of LM was not influenced by SW except for a reduced 18:0 percentage for XHi vs. Av. The sensory score was less for XHi vs. Av for odor in fresh LD and SM, and less for Hi and XHi vs. Av for aroma in fresh LM; scores for color, drip loss, marbling, and acceptability were unaffected by SW. As for cooked muscles, none of the scores for color, aroma, flavor, juiciness, tenderness, and acceptability was affected by SW, except for a greater LD color score for Hi and XHi vs. Av. Collectively, the results suggested that the increased yield of the carcass and belly due to increased SW is outbalanced negatively by excessive backfat deposition in production efficiency, whereas the SW increase exerts little influence on overall sensory quality of fresh or cooked meat. Production of non-lean market pigs overweighing 115 kg therefore will be uneconomical unless consumers pay a substantial premium for the over-fattened pork.

Keywords: Finishing pig; Slaughter weight; Loin; Ham; Physicochemical characteristics; Sensory attribute

INTRODUCTION

The slaughter weight (SW) of finishing pigs is a significant economic and technical factor that greatly affects pork quality as well as production efficiency and profitability of pig production [13]. Lee et al. [4] and Park et al. [57] have shown that backfat thickness (BFT), dressing percentage, and pork belly yield increased as the SW of finishing pigs in the range of 110–138 kg increased. Subsequently, Jeong et al. [8] and Park and Lee [1] analyzed the pooled data of these studies [47] and showed that sensory scores of fresh loin and ham, including those for marbling, were improved as SW increased from 110 to 125 kg, with no further changes beyond 125 kg, although sensory quality attributes of cooked loin and ham were virtually unaffected by SW. Moreover, the SW increase was found to render an increase in the redness of meat color, which is the most important factor determining the retail selection of meat [9,10].

The SW seemingly influences meat quality primarily through its effects on fat metabolism. Intra-muscular fat (IMF), which increases marbling of fresh meat as well as the sensory attributes of cooked meat, including flavor, is known to increase with an increase in SW [11,12]. The IMF in the pork loin in the previous studies [47] indeed increased with the increase of SW, albeit to a limited extent, which did not influence sensory properties of cooked meat [8]; limited data regarding IMF for the ham precluded any assessment regarding the effect of SW on meat quality. More specifically, fatty acid (FA) composition of the meat also influences meat quality and palatability [9,1113], but the effects due to the increased age or SW of finishing pigs on FA composition of the loin in the aforementioned studies [47] were not consistent.

Besides SW, genetic leanness or whole-body adiposity represented by BFT of growing pigs, as well as their plane of nutrition, also influences pork quality [11,1416]. It has been well documented in growing pigs that the marbling fat is greater in pig carcasses having greater BFT than those with less BFT [13] and that average daily gain (ADG) increases with an increase in dietary energy density or lysine:calorie ratio, whereas BFT and IMF increase with reduced ADG at a suboptimal lysine:calorie ratio [1719]. In this connection, domestic market pigs have much greater BFT than those in Western countries to varying extents, as could be exemplified by their BFT spanning from 20 to over 30 mm, with an average of 21.8 mm at a 117-kg average market weight [20], compared to 19-mm BFT and 130-kg live weight for typical market pigs in the U.S.A. [21, 22]. Regarding the previous studies [48], the experimental pigs had 22.0 mm of overall average BFT at 122.5-kg SW, which fell on the medium lean category domestically. However, the diets used in those studies [47] were far from common in that their energy densities (3.0–3.2 Mcal DE/kg) were much less than the NRC [21,23] recommendation (3.4 Mcal DE/kg), whereas their lysine content (0.85% or 0.90%) were greater than the latter (0.60% to 0.80%). It is therefore unknown if non-lean pigs having high BFT could be used to improve their meat quality under commercial production conditions where the plane of nutrition is commonly equal to or greater than the NRC [21] recommendation.

The present study was aimed at assessing the feasibility of increasing the SW of non-lean pigs reared on medium-high planes of nutrition from the standpoints of production efficiency and pork quality.

METHODS

Feeding and slaughtering

All experimental protocols involving animals of the present study were approved by the Institutional Animal Care and Use Committee (IACUC) of Gyeongsang National University (GNU-210906-P0077). The (Landrace × Yorkshire) × Duroc finisher pigs with relatively high BFT used in the present study had been reared on commercial grower and finisher diets on a commercial swine farm with their planes of nutrition comparable to those of NRC [21] recommendations for growing-finishing pigs with a high-medium lean growth rate (Table 1) as described by Yang et al. [16,24]. The present experiment was performed under a 2 (sex) × 3 [SW; ‘Average’ (Av; 115 kg), ‘High’ (Hi; 125 kg), and ‘Extra-high’ (XHi; 135 kg)] factorial arrangement of treatments. Each of the Av, Hi, and XHi groups was assigned six barrows and six gilts weighing approximately 90, 100, and 110 kg, respectively, in six pens of 17 pigs, with one pen for each sex × SW combination, after which the 36 selected animals were fattened 5 more wks within their own pens. The experimental animals were transported to a local abattoir upon measurement of their live weights and slaughtered the following day. After scalding, grading as per MAFRA [25] standards, and overnight chilling of the carcass, the belly, ham, and loin were dissected from the left half-carcass of each animal and transported to the laboratory in a refrigerator car. The BFT measurement provided by the abattoir was adjusted for the desired SW using the slope of regression of BFT on SW in each sex as described by Yang et al. [16].

Table 1. Phase-feeding program and nutritional specification of the diets for the experimental animals
Item Diet
Phase I1) Phase II2) Phase III3)
Interval of BW (kg) 20-43 43–72 > 72 kg
Nutritional specification
 ME (Mcal/kg) 3.35 3.35 3.25
 Total lysine (%) 1.20 1.02 0.80

Each was a commercial diet, with its composition of ingredients unavailable. The pigs used for the present experiment were fed the phase I, -II, and -II diets during the indicated intervals of body weights, respectively.

BW, body weight; ME, metabolizable energy.

Download Excel Table
Physicochemical analysis

For the evaluation of the yield and muscle:fat balance of the belly, this primal was weighed and cut at the 11th rib where the fat content of the primal is greatest [2]. After removal of a 1 cm-thick slice from the cut surface, the cross-section of the slice at the 11th rib was photographed at a fixed vertical distance followed by quantitating the areas for the fat and muscle of the photo image by computer scanning. As for the loin and ham, the longissimus dorsi muscle (LM) and semimembranosus muscle (SM) were removed from the former and latter, respectively, for physicochemical and sensory analyses described below.

Physicochemical characteristics of the muscle, including pH, CIE [26] color, drip loss, cooking loss, and Warner-Bratzler shear force were determined as previously described [14,27]. Contents of moisture, protein, and fat of the muscle were determined by the oven-drying and Kjeldahl and Soxhlet extraction methods, respectively, following the procedures of AOAC [28]. Composition of FA of the muscle was determined by gas chromatography using the capillary column following extraction of total lipids by the method of Folch et al. [29] as described [14,27].

Sensory evaluation

The sensory attribute of the muscle was evaluated by seven panelists who had been trained in the intramural meat science and processing lab following the guidelines of Meilgaard et al. [30]. Briefly, each attribute was scored according to a 9-point hedonic scale ranging from 1 for the poorest to 9 for the best regardless of the positive or negative nature of the evaluated attribute as described by Jin et al. [27] and Park et al. [5,6].

Statistical analysis

All data were analyzed using the General Linear Model procedure of SAS (SAS/STAT Software for PC. Release 9.2, SAS Institute, Cary, NC, USA). The statistical model included the sex and SW, i.e., main effects, as well as their interaction as fixed errors in the analysis for the carcass variables as well as the physicochemical variables of the belly, LM, and SM; as for sensory evaluation, the model included the experimental animal (pig) nested within sex × SW (pig [sex × S] ) and the panelist in addition to the main effects and their interaction. In all analyses, the pig was the experimental unit. The main effects and their interaction, which were tested using the pig (sex × SW) and the pig as the error terms for the sensory variables and the rest of the variables, respectively, were judged significant when the corresponding p-value was 0.05 or less. Means were compared by a t-test by virtue of the PDIFF option of the SAS program only when the p-value for the main effect or the interaction of the main effects was significant.

RESULTS

Quantitative characteristics of the carcass and its pork belly

The dressing percentage was greater for the Hi and XHi groups than for the Av group, with no difference between Hi and XHi (Table 2). BFT was also greater for the Hi (31.2 mm) and XHi (29.3 mm) groups than for the Av group (25.0 mm). The Av group pigs yielded 11 Grade 1+ or 1 carcasses and only one Grade 2, whereas in the Hi and XHi groups, 20 carcasses fell on Grade 2, with four receiving Grade 1+ or 1. The weight of the belly, as expected, was greatest for the XHi group and least for the Av group. Moreover, the SW × sex interaction for this variable was significant, but no difference was detected between the barrow and gilt within any of the three SW groups. The percent yield of the belly per whole carcass was greater for the XHi group (12.50%) than for the Av group (11.71%), with no difference between the former and Hi group (12.13%). However, the ratio of the area for the inter-muscular fat per total cross-section of the belly at the 11th rib did not differ across the three different SW groups.

Table 2. Physical characteristics of the carcass and the belly of finishing pigs at different slaughter weights
Item Av (115 kg) Hi (125 kg) XHi (135 kg) SEM p-value
B (n=6) G (n=6) B (n=6) G (n=6) B (n=6) G (n=6) SW S SW × S
Live wt (kg) 115.5 115.9 123.7 124.0 137.6 132.3 1.9 < 0.01 0.34 0.27
Age at slaughter (d) 177 184 191 198 205 212 0
Carcass wt (kg) 86.6 86.2 97.6 100.4 106.7 102.0 1.5 < 0.01 0.55 0.07
Dressing (%) 75.1 74.4 78.9 79.4 77.5 77.1 1.0 < 0.01 0.80 0.84
BFT1) 25.4 24.6 30.9 27.6 31.4 31.0 1.3 < 0.01 0.22 0.59
Number of carcasses by grade
 1+ 2 3 0 1 0 0
 1 3 3 2 0 1 0
 2 1 0 4 5 5 6
Belly
 Wt2) (kg) 5.10 5.00 5.79 6.21 6.75 6.30 0.16 < 0.01 0.74 0.04
 Yield2)3) (%) 11.80 11.61 11.93 12.32 12.66 12.35 0.13 0.01 0.87 0.35
 Fat2)4) (%) 39.0 36.5 39.7 37.7 38.4 38.4 2.4 0.92 0.45 0.86

Backfat thickness; Adjusted for the desired live wt indicated at the column heading.

Only the primal cut from the left half-carcass was measured.

100 × 2 × weight of the left-side belly/wt of the whole carcass.

100 × inter-muscular fat area/total area of the cross-section of the belly at the 11th rib.

Av, average; Hi, high; XHi, extra-high; B, barrow; G, gilt; SW, slaughter weight; S, sex; BFT, backfat thickness.

Download Excel Table
Physicochemical characteristics of the muscle

None of the physicochemical properties of LM measured in the present study, including pH, lightness (L*), redness (a*), drip loss, cooking loss, Warner-Bratzler shear force, and the content of each of moisture, protein, and fat, differed among the three groups with different SW or between the barrow and gilt (Table 3). The pH value, lightness, redness, and drip loss of SM were also not influenced by the SW or sex. The cooking loss of SM was less for the Hi group vs. Av and XHi groups. The moisture and protein contents of SM were not influenced by the SW or sex. However, fat content of this muscle was greater for the XHi group (2.64%) vs. Av (1.83%) and Hi (2.04%). Moreover, the fat content of SM was correlated with SW (r = 0.55; p < 0.01).

Table 3. Physicochemical characteristics of the longissimus dorsi muscle and Semimembranosus muscle of finishing pigs at different slaughter weights1)
Item Av (115 kg) Hi (125 kg) XHi (135 kg) SEM p-value
B G B G B G SW S SW × S
Longissimus dorsi muscle
 pH 5.66 5.63 5.64 5.70 5.66 5.66 0.02 0.45 0.59 0.13
 CIE L* 49.2 50.3 51.1 49.6 48.6 50.1 0.8 0.46 0.56 0.12
 CIE a* 6.38 6.21 5.79 5.53 5.87 5.36 0.34 0.09 0.27 0.88
 DL (%) 5.95 5.21 6.49 4.94 5.34 5.48 0.55 0.86 0.12 0.31
 CL (%) 23.4 23.7 25.0 23.1 24.4 24.6 0.9 0.60 0.54 0.41
 SF (kg/cm2) 3.99 3.89 3.84 4.22 3.67 3.09 0.38 0.81 0.58 0.82
 Chemical composition (%)
  Moisture 73.4 73.7 73.5 73.5 73.8 73.9 0.3 0.62 0.97 1.00
  Protein 22.5 22.1 22.9 22.4 21.9 22.7 0.3 0.47 0.90 0.12
  Fat 2.19 1.95 1.88 2.22 1.95 1.68 0.28 0.60 0.80 0.47
Semimembranosus muscle
 pH 5.62 5.60 5.55 5.62 5.59 5.60 0.03 0.64 0.42 0.21
 CIE L* 50.9 51.8 53.4 50.9 52.8 53.2 0.9 0.20 0.57 0.12
 CIE a* 8.40 8.25 8.56 8.24 9.27 8.68 0.42 0.25 0.30 0.87
 DL (%) 5.81 5.89 6.87 6.03 6.67 6.39 0.40 0.21 0.33 0.56
 CL (%) 25.7 26.7 22.1 22.6 26.2 26.3 1.3 < 0.01 0.62 0.95
 SF (kg/cm2) 4.15 3.18 3.18 3.17 3.39 3.33 0.29 0.25 0.15 0.19
 Chemical composition (%)
  Moisture 73.6 73.7 73.5 73.5 73.8 73.9 0.3 0.70 0.62 0.74
  Protein 22.3 21.8 21.9 21.6 21.6 22.0 0.3 0.65 0.61 0.23
  Fat 1.89 1.76 2.40 1.68 2.83 2.45 0.25 < 0.01 0.06 0.51

Data are means of six animals in each SW × S combination.

Av, average; Hi, high; XHi, extra-high; B, barrow; G, gilt; SW, slaughter weight; S, sex; DL, drip loss; CL, cooking loss; SF, Warner-Bratzler shear force.

Download Excel Table

The percentages of myristic acid (14:0) and palmitic acid (16:0) out of total FA by weight in LM did not differ among the SW groups or between the sexes (Table 4). However, the stearic acid (18:0) percentage of LM was less for the XHi group (12.1%) than for the Av group (13.2%) and was not different between the XHi and Hi (12.7%) groups. Percentages of palmitoleic (16:1), oleic (18:1), linoleic (18:2), and arachidonic (20:4) acids did not differ among the three different SW groups or between the sexes. Effects of the SW and sex on percentages of total saturated fatty acids (SFA), total unsaturated fatty acids (UFA), n-3 and n-6 FA were also non-significant.

Table 4. Composition of fatty acids of the longissimus dorsi muscle and Semimembranosus muscle of finishing pigs at different slaughter weights1)
Item Av (115 kg) Hi (125 kg) XHi (135 kg) SEM p-value
B G B G B G SW S SW×S
Longissimus dorsimuscle
 14:0 1.91 1.83 1.69 1.98 1.88 1.82 0.10 0.93 0.53 0.13
 16:0 25.9 25.6 24.6 25.9 25.4 25.0 0.6 0.59 0.66 0.26
 18:0 13.5 12.9 12.2 13.2 12.2 11.9 0.4 0.05 0.88 0.22
 16:1 3.84 3.95 4.12 3.99 3.87 3.98 0.27 0.79 0.82 0.84
 18:1 38.6 39.3 39.7 40.2 39.5 40.9 0.9 0.39 0.28 0.90
 18:2 9.1 10.2 11.3 9.3 10.9 10.5 1.2 0.68 0.67 0.45
 20:4 4.04 3.22 3.49 2.37 3.08 2.75 0.46 0.23 0.06 0.70
 Others 3.2 3.0 3.0 3.0 3.2 3.2
 Total 100.0 100.0 100.0 100.0 100.0 100.0
  SFA 41.6 40.7 38.8 41.4 39.8 39.0 0.9 0.16 0.64 0.09
  UFA 58.4 59.3 61.2 58.6 60.2 61.0 0.9 0.16 0.68 0.09
  n-3 0.42 0.35 0.38 0.48 0.44 0.45 0.04 0.26 0.73 0.10
  n-6 13.5 13.8 15.2 12.1 14.4 13.6 1.3 0.94 0.27 0.44
Semimembranosus muscle
 14:0 2.14 2.00 1.68 1.92 1.72 1.71 0.10 < 0.01 0.73 0.20
 16:0 24.7 24.8 23.4 24.1 23.8 23.2 0.4 < 0.01 0.86 0.25
 18:0 11.5 11.7 11.4 11.2 11.4 10.4 0.4 0.32 0.34 0.37
 16:1 3.75 3.96 3.86 3.88 3.53 3.93 0.24 0.81 0.29 0.75
 18:1 39.4 41.0 38.4 38.3 37.5 39.0 1.2 0.22 0.34 0.74
 18:2 11.9 10.6 13.6 13.2 13.9 13.9 0.8 0.01 0.40 0.72
 20:4 2.89 2.56 4.30 3.96 4.40 4.18 0.60 0.03 0.55 0.99
 Others 3.7 3.5 3.4 3.4 3.7 3.7
 Total 100.0 100.0 100.0 100.0 100.0 100.0
  SFA 38.7 38.8 36.8 37.5 37.3 35.7 0.7 0.01 0.70 0.26
  UFA 61.3 61.2 63.2 62.5 62.7 64.3 0.7 0.01 0.70 0.27
  n-3 0.54 0.47 0.52 0.53 0.55 0.56 0.04 0.46 0.62 0.56
  n-6 15.3 13.6 18.4 17.7 18.8 18.5 1.4 0.01 0.42 0.86

Data, expressed as percentages of total fatty acids by weight, are means of six animals in each SW × S combination.

Av, average; Hi, high; XHi, extra-high; B, barrow; G, gilt; SW, slaughter weight; S, sex; SFA, saturated fatty acids; UFA, unsaturated fatty acids.

Download Excel Table

In SM, the percentage of myristic acid was less for the Hi (1.8%) and XHi (1.7%) groups than for the Av group (2.1%). The palmitic acid percentage of SM was also less for the Hi (23.7%) and XHi (23.5%) groups vs. the Av (24.7%). Conversely, the percentage of linoleic acid was greater for the Hi (13.4%) and XHi (13.9%) groups than for the Av (11.3%); the arachidonic acid percentage was also greater for the Hi (4.1%) and XHi (4.3%) groups vs. Av (2.7%). However, percentages of stearic, palmitoleic, and oleic acids did not differ among the three different SW groups. The percentage of SFA was less for the Hi and XHi groups than for the Av group, whereas the opposite was true for UFA and n-6 FA. The n-3 FA percentage of SM, however, did not differ among the three groups with different SW.

Sensory evaluation

The score for the color for fresh LM did not differ among the groups with different SW or between the sexes (Table 5). The aroma score for fresh LM was less for the Hi (6.69) and XHi (6.67) groups than for the Av group (6.88). The odor score also was less for the Hi (6.74) and XHi (6.68) groups vs. the Av group (6.90). However, scores for the drip loss, marbling, and acceptability for this muscle were not influenced by the SW or sex. The scores for fresh SM did not differ among the three SW groups or between the sexes, except for the odor score, which was less for the XHi group (6.50) than for the Av (6.75) and Hi (6.70) groups. The acceptability score was greater for the Av group than for the XHi group only in gilts and also for the gilt vs. barrow only within the Hi group, with either main effect insignificant.

Table 5. Effects of the slaughter weight of finishing pigs on sensory attributes of their muscles1)
Item Av (115 kg) Hi (125 kg) XHi (135 kg) SEM p-value
B G B G B G SW S SW×S
Fresh muscle
Longissimus dorsimuscle
  Color 6.60 6.38 6.50 6.83 6.69 6.48 0.17 0.58 0.82 0.19
  Aroma 6.93 6.83 6.60 6.79 6.74 6.60 0.09 0.04 0.83 0.14
  Odor 6.93 6.88 6.69 6.79 6.62 6.74 0.06 < 0.01 0.23 0.28
  Drip loss2) 6.93 6.86 6.81 6.76 6.76 6.71 0.07 0.07 0.31 0.98
  Marbling 6.79 6.76 6.76 6.67 6.83 6.60 0.19 0.94 0.45 0.85
  Acceptability 6.93 6.71 6.52 6.79 6.74 6.62 0.12 0.36 0.82 0.15
Semimembranosus muscle
  Color 6.48 6.71 6.48 6.67 6.57 6.41 0.16 0.78 0.50 0.39
  Aroma 6.62 6.71 6.57 6.81 6.55 6.50 0.08 0.08 0.14 0.19
  Odor 6.71 6.79 6.60 6.81 6.45 6.55 0.09 0.02 0.09 0.69
  Drip loss 6.43 6.67 6.57 6.86 6.81 6.83 0.11 0.06 0.05 0.47
  Marbling 6.71 6.86 6.50 6.76 6.62 6.50 0.15 0.33 0.45 0.45
  Acceptability 6.52ab 6.83a 6.41b 6.76a 6.57ab 6.40b 0.11 0.23 0.07 0.04
Cooked muscle
Longissimus dorsimuscle
  Color 6.62 6.64 6.86 6.79 6.76 6.86 0.04 < 0.01 0.65 0.16
  Aroma 6.74 6.64 6.67 6.69 6.67 6.69 0.05 0.96 0.70 0.41
  Flavor 6.93 6.76 6.81 6.74 6.90 6.69 0.09 0.72 0.05 0.72
  Juiciness 6.24b 6.33ab 6.24b 6.71a 6.76a 6.33ab 0.15 0.22 0.70 0.02
  Tenderness 6.86 6.83 6.38 6.93 6.83 6.71 0.22 0.68 0.46 0.27
  Acceptability 6.60 6.74 6.36 6.81 6.81 6.60 0.16 0.77 0.36 0.15
Semimembranosus muscle
  Color 6.74 6.69 6.67 6.74 6.67 6.71 0.06 0.92 0.63 0.58
  Aroma 6.67 6.62 6.60 6.42 6.50 6.62 0.06 0.32 0.39 0.34
  Flavor 6.69 6.79 6.81 6.67 6.76 6.79 0.09 0.90 0.91 0.39
  Juiciness 6.38 6.33 6.48 6.31 6.40 6.36 0.12 0.95 0.36 0.81
  Tenderness 6.48 6.79 6.86 6.79 6.74 6.60 0.16 0.45 0.81 0.32
  Acceptability 6.45 6.42 6.76 6.62 6.71 6.62 0.09 0.28 0.84 0.18

Each sensory attribute was scored by seven trained panelists according to a 9-point hedonic scale ranging from 1 for the worst/least to 9 for the best/most, with an exception for drip. Data are means of six animals in each SW × S combination.

Point scores 1 and 9 correspond to the most and least, respectively.

Means in a same row with no common superscript differ (p < 0.05).

Av, average; Hi, high; XHi, extra-high; B, barrow; G, gilt; SW, slaughter weight; S, sex.

Download Excel Table

The color score for cooked LM was greater for the Hi (6.82) and XHi (6.81) groups than for the Av group (6.63). However, neither the SW nor the sex had any significant effect on any of the scores for aroma, flavor, juiciness, tenderness, and acceptability for cooked LM, except for the flavor score, which was greater for the barrow (6.88) than for the gilt (6.73). In addition, the juiciness score was greater for the XHi group than for the Av group only in barrows and also for the gilt vs. barrow only in the Hi group. In cooked SM, none of the scores for the color, aroma, flavor, juiciness, tenderness, and acceptability was affected by the SW or sex.

DISCUSSION

The SW of finishing pigs are determined by various internal and external factors such as the genetic potential of growth performance in the individual pig itself, social and cultural traditions, the needs of consumers and packers, and the grading standards [1,3133]. For example, finishing pigs in Korea are slaughtered at around 115 kg on average to meet the required range of CW for the top grade, Grade 1+, which should be 83 kg or greater but less than 93 kg [25]; this differs with the SW of 160 kg or greater in Italy, where big carcasses are needed to make the dry-cured hams, and the SW range of around 100–140 kg in the U.S., which depends on pork productivity and the demand of the packers [131 kg on average; 1,22,31,32]. It has been reported that the increase of SW results in a decreased production cost per unit weight of pork accompanied by slight increases in the dressing percentage and the yield percentage of the belly although growth rate and feed efficiency decrease following the increase of SW due to increased fat deposition [1,4,6,8,32]. It was therefore the rationale of the present study that if CW could be increased separately from the carcass grading system, the profitability would improve and the flavor of the meat might also improve [12,34], resulting in the improvement of pork quality, as was expected of the carcasses from the Hi and XHi groups of the present study mostly exceeding the 97-kg upper limit of Grade 1.

In this study conducted on non-lean finishing pigs, the BFT was excessive when the SW was greater than the standard (115 kg), while the dressing percentage and the yield percentage of the pork belly slightly increased, which was consistent with published results [1,4,6,8,32]. In addition, the finding of this study that the ratio of inter-muscular fat area in the cross section of pork belly at the 11th rib, where excessive fat - so called ‘caky fat’ - deposition occurs, was within the normal range regardless of SW, was also consistent with the finding of Park et al. [2] that the fat weight ratios of pork belly slices between the 11th and 12th ribs in 85–150-kg finishing pigs were independent of SW. On the other hand, the increases of redness and marbling of LM due to increased SW detected in a data set of pooled results [8], which were inconsistently observed in the relevant individual studies [47], were not detected in the present study.

The FA composition of IMF is an important factor significantly influencing the eating quality of meat [9,13,35,36]. For instance, mono-UFA, especially oleic acid, is known to have a positive influence on eating quality of pork, with SFA and n-3 FA exerting negative effects; however, the increased percentages of UFA, including linoleic acid, arachidonic acid, and n-3 FA, with reduced SFA, in SM did not influence any sensory attribute of cooked meat. These SW-associated changes in FA composition, which were not apparent in LM in the present study, have been observed in LM as well by Ba et al. [34]. Reasons for these differential effects of SW on FA composition in these two studies are not clear at present, but are probably related to accumulation of dietary FA within IMF, which, de facto, cannot be separated from de novo FA synthesis [12,34]. In this regard, it has been well documented that polyunsaturated fatty acids (PUFA) represented by linoleic acid, a n-6 FA, and n-3 FA such as linolenic acid in the diet are mostly incorporated into the fat depot instead of being broken down in the body [9,13,36]. Moreover, the finisher diet used for the present study, which contained 2.5% of lard and 7% of corn distillers dried grains with solubles, respectively (personal communication with the manufacturer of the diet), rich in UFA including linoleic acid [37,38], was provided to the Hi and XHi groups longer than to the Av group for about two and four weeks, respectively. Apart from the dietary influence on fat metabolism, the changes in FA composition of IMF due to the increased SW may well be a merit of heavy market pigs in terms of public health, because UFA, especially n-3 FA, lowers the risk of cardiovascular diseases whereas SFA increases the risk [35,39,40].

The aroma and odor scores of fresh LM and the odor score of fresh SM decreased due to an increase in SW, but all of these items showed a normal range of scores and the differences among the experimental groups were minimal. It is known that PUFA such as linoleic acid and n-3 FA are oxidized during the preservation of fresh meat, resulting in the generation of off-odor substances, low sensory odor scores, and low flavor of cooked meat [9,35,41]. In this study, it is assumed that the reason for low odor scores due to the increase of SW was not related to fat rancidity because the percentage of linoleic and n-3 FA in LM and SM was neither high nor correlated with odor score. Considering these results and the lack of differences among the three SW groups in other attributes, it is interpreted that the increase in SW has little to no effect on the overall sensory quality of fresh meat, which was not consistent with the increase of sensory quality of fresh meat due to the increase of SW in lean pigs in previous studies [1,5,6,8].

The BFT and IMF content of finishing pigs, in general, increase with the increase in age or SW [1,11,12,32,34], although consequences of this on eating quality of pork are not consistent between studies [13,33,42,43]. The IMF content of LM in the present study was neither influenced by SW, with an overall average of 2.0%, nor was correlated with the sensory attributes associated with eating quality, which was consistent with the results of Jeong et al. [8] for the lean pigs reared on the low-energy diet with their SW and overall average IMF content being 110–138 kg and 2.6%, respectively. In contrast, Hwang et al. [44] have reported that the IMF content of LM of market pigs increased approximately from 2.1% to 3.0% between their carcass weights below 90 kg and over 100 kg, respectively, which were comparable to those for the Av and XHi groups of the present study, respectively, and that the IMF content was positively correlated with flavor and palatability of cooked LM. Furthermore, Hoa et al. [45] have reported that the IMF content was greater for pigs with their BFT over 20 mm (6.7%) than for those with < 20-mm BFT (4.1%) in market pigs weighing 112 kg on average and was also positively correlated with BFT, flavor, juiciness, and acceptability of cooked LM. Overall, improvement in sensory attributes of LM associated with an increased SW or BFT is apparently dependent on a concomitant increase in IMF in these studies, suggesting a key role for IMF in the eating quality of cooked LM. In a similar context, the differential in the IMF content of SM between the different SW groups in the present study probably was not significant enough to make any difference in sensory attributes.

In conclusion, the excessive back fat deposition due to an increase in SW of non-lean finishing pigs is expected to result in a decrease in production efficiency outweighing the advantages of the slight increases in the dressing percentage and the yield percentage of the pork belly accruing from the increased SW. Although the increase of SW resulted in increases in the IMF content and ratios of a few UFA in SM and a decrease in the ratio of SFA, it had practically little effect on the overall sensory quality of fresh and cooked LM as well as SM. As such, production of non-lean pigs heavier than 115 kg will be disadvantageous economically unless consumers pay a substantial premium for the pork of over-fattened market pigs.

Competing interests

No potential conflict of interest relevant to this article was reported.

Funding sources

This work was supported by Gyeongsang National University Grant in 2021.

Acknowledgements

Not applicable.

Availability of data and material

Upon reasonable request, the datasets of this study can be available from the corresponding author.

Authors’ contributions

Conceptualization: Lee CY, Song DH, Song YM.

Data curation: Lee CY, Song YM.

Formal analysis: Kim HW, Jin SK, Song YM.

Methodology: Kim HW, Jin SK.

Software: Oh SH, Song DH, Jin SK.

Validation: Jin SK, Song YM.

Investigation: Oh SH, Lee CY, Song YM.

Writing - original draft: Oh SH, Lee CY, Song YM.

Writing - review & editing: Oh SH, Lee CY, Song DH, Kim HW, Jin SK, Song YM.

Ethics approval and consent to participate

All experimental protocols involving animals of the present study were approved by the Institutional Animal Care and Use Committee (IACUC) of Gyeongsang National University (GNU-210906-P0077).

REFERENCES

1.

Park BC, Lee CY. Feasibility of increasing the slaughter weight of finishing pigs. J Anim Sci Technol. 2011; 53:211-22

2.

Park MJ, Park BC, Ha DM, Kim JB, Jang KS, Lee DH, et al. Effects of increasing market weight of finishing pigs on backfat thickness, incidence of the ‘caky-fatty’ belly, carcass grade, and carcass quality traits. J Anim Sci Technol. 2013; 55:195-202

3.

Park BC, Ha DM, Park MJ, Jin SK, Park JH, Lee CY. Effects of the decreased carcass grade of finishing pigs due to increasing market weight on carcass quality traits and physicochemical and sensory quality characteristics of the loin and belly. J Anim Sci Technol. 2013; 55:203-10

4.

Lee CY, Kwon OC, Ha DM, Shin HW, Lee JR, Ha YJ, et al. Growth efficiency, carcass quality characteristics and profitability of finishing pigs slaughtered at 130 vs. 110 kg. J Anim Sci Technol. 2006; 48:493-502

5.

Park MJ, Ha DM, Shin HW, Lee SH, Kim WK, Ha SH, et al. Growth efficiency, carcass quality characteristics and profitability of ‘high’-market weight pigs. J Anim Sci Technol. 2007; 49:459-70

6.

Park MJ, Jeong JY, Ha DM, Han JC, Sim TG, Park BC, et al. Effects of dietary energy level and slaughter weight on growth performance and grades and quality traits of the carcass in finishing pigs. J Anim Sci Technol. 2009; 51:143-54

7.

Park MJ, Jeong JY, Ha DM, Park JW, Sim TG, Yang HS, et al. Relationships of the slaughter weight to growth performance and meat quality traits in finishing pigs fed a low-energy diet. J Anim Sci Technol. 2009; 51:135-42

8.

Jeong JY, Park BC, Ha DM, Park MJ, Joo ST, Lee CY. Effects of increasing slaughter weight on production efficiency and carcass quality of finishing gilts and barrows. Korean J Food Sci Anim Resour. 2010; 30:206-15

9.

Burnett DD, Legako JF, Phelps KJ, Gonzalez JM. Biology, strategies, and fresh meat consequences of manipulating the fatty acid composition of meat. J Anim Sci. 2020; 98skaa033

10.

Seideman SC, Cross HR, Smith GC, Durland PR. Factors associated with fresh meat color: a review. J Food Qual. 1984; 6:211-37

11.

Joo ST, Kim GD. Meat quality traits and control technologies.In In: Joo ST, editor.editor Control of meat quality. Kerala: Research Signpost. 2011; p p. 1-29

12.

Lawrence TLJ, Fowler VR, Novakofski JE. Growth of farm animals. 3rd ed Wallingford: CABI. 2012

13.

Wood JD, Enser M, Fisher AV, Nute GR, Sheard PR, Richardson RI, et al. Fat deposition, fatty acid composition and meat quality: a review. Meat Sci. 2008; 78:343-58

14.

Lee CH, Jung DY, Choi JS, Jin SK, Lee CY. Effects of the plane of nutrition on physicochemical characteristics and sensory quality traits of the muscle in finishing pigs. Korean J Food Sci Anim Resour. 2014; 34:516-24

15.

Choi JS, Jin SK, Lee CY. Assessment of growth performance and meat quality of finishing pigs raised on the low plane of nutrition. J Anim Sci Technol. 2015; 57:37

16.

Yang BS, Kim MH, Choi JS, Jin SK, Park MJ, Song YM, et al. Effects of the plane of nutrition for grower pigs on their grow-finish performance and meat quality in winter. J Anim Sci Technol. 2019; 61:1-9

17.

Beaulieu AD, Williams NH, Patience JF. Response to dietary digestible energy concentration in growing pigs fed cereal grain-based diets. J Anim Sci. 2009; 87:965-76

18.

Castell AG, Cliplef RL, Poste-Flynn LM, Butler G. Performance, carcass and pork characteristics of castrates and gilts self-fed diets differing in protein content and lysine:energy ratio. Can J Anim Sci. 1994; 74:519-28

19.

Witte DP, Ellis M, McKeith FK, Wilson ER. Effect of dietary lysine level and environmental temperature during the finishing phase on the intramuscular fat content of pork. J Anim Sci. 2000; 78:1272-6

20.

KAPE. A report on “Results on measurements of pork quality traits of cold pig carcasses” [Internet]. Institute for animal products quality evaluation 2020[cited 2021 Nov 9]https://www.ekape.or.kr

21.

NRC [Natinoal Research Council]. Nutrient requirements of swine. 11th ed Washington, DC: National Academy Press. 2012

22.

USDA [United States Department of Agriculture]. USDA statistics/2019 agricultural statistics, annual [Internet]. 2021[cited 2021 Nov 9]https://www.nass.usda.gov

23.

NRC [Natinoal Research Council]. Nutrient requirements of swine. 10th rev. ed Washington, DC: National Academy Press. 1998

24.

Yang SW, Kim MH, Choi JS, Jin SK, Park MJ, Song YM, et al. Effects of the plane of nutrition during the latter grower and entire finisher phases on grow-finish pig performance in summer. J Anim Sci Technol. 2019; 61:10-7

25.

MAFRA [Ministry of Agriculture, Food and Rural Affairs]. Grading, standards for livestock products. Seoul: Ministry of Agriculture, Food and Rural Affairs. 2014Notification No. 2014-4

26.

CIE [Commission Internationale de l’Eclairage]. Colorimetry. 2nd edViennaCommission Internationale de l’Eclairage 1986 CIE Publication No. 15.2

27.

Jin SK, Kim IS, Hur SJ, Hah KH, Kim BW. Effects of feeding period on carcass and objective meat quality in crossbred longissimus muscle. J Anim Sci Technol. 2004; 46:811-20

28.

AOAC [Association of Official Analytical Chemists] International. Official methods of analysis of AOAC International. 18th ed Gaithersburg, MD: AOAC International. 2006

29.

Folch J, Lees M, Sloane Stanley GHS. A simple method for the isolation and purification of total lipides from animal tissues. J Biol Chem. 1957; 226:497-509

30.

Meilgaard MC, Civille GV, Carr BT. Sensory evaluation techniques. 4th ed Boca Raton, FL: CRC Press. 2006

31.

Kim YS, Kim SW, Weaver MA, Lee CY. Increasing the pig market weight: world trends, expected consequences and practical considerations. Asian-Australas J Anim Sci. 2005; 18:590-600

32.

Wu F, Vierck KR, DeRouchey JM, O’Quinn TG, Tokach MD, Goodband RD, et al. A review of heavy weight market pigs: status of knowledge and future needs assessment. Transl Anim Sci. 2017; 1:1-15

33.

Channon HA, D’Souza DN, Dunshea FR. Diet composition and slaughter age up to 24 weeks have minimal impact on pork eating quality of loin steaks and silverside roasts from female pigs. Meat Sci. 2018; 135:94-101

34.

Ba HV, Seo HW, Seong PN, Cho SH, Kang SM, Kim YS, et al. Live weights at slaughter significantly affect the meat quality and flavor components of pork meat. Anim Sci J. 2019; 90:667-79

35.

Pettigrew JE, Esnaola MA. Swine nutrition and pork quality: a review. J Anim Sci. 2001; 79:E316-42

36.

Averette Gatlin L, See MT, Hansen JA, Odle J. Hydrogenated dietary fat improves pork quality of pigs from two lean genotypes. J Anim Sci. 2003; 81:1989-97

37.

Rohman A, Triyana K, Sismindari S, Erwanto Y. Differentiation of lard and other animal fats based on triacylglycerols composition and principal component analysis. Int Feed Res J. 2012; 19:475-9

38.

Xu G, Baidoo SK, Johnston LJ, Bibus D, Cannon JE, Shurson GC. Effects of feeding diets containing increasing content of corn distillers dried grains with solubles to grower-finisher pigs on growth performance, carcass composition, and pork fat quality. J Anim Sci. 2010; 88:1398-410

39.

Lenighan YM, McNulty BA, Roche HM. Dietary fat composition: replacement of saturated fatty acids with PUFA as a public health strategy, with an emphasis on α-linolenic acid. Proc Nutr Soc. 2019; 78:234-45

40.

Visioli F, Poli A. Fatty acids and cardiovascular risk. Evidence, lack of evidence, and diligence. Nutrients. 2020; 12:3782

41.

Melton SL. Effects of feeds on flavor of red meat: a review. J Anim Sci. 1990; 68:4421-35

42.

Huff-Lonergan E, Baas TJ, Malek M, Dekkers JCM, Prusa K, Rothschild MF. Correlations among selected pork quality traits. J Anim Sci. 2002; 80:617-27

43.

Fernandez X, Monin G, Talmant A, Mourot J, Lebret B. Influence of intramuscular fat content on the quality of pig meat — 2. Consumer acceptability of m. longissimus lumborum. Meat Sci. 1999; 53:67-72

44.

Hwang YH, Lee SJ, Lee EY, Joo ST. Effects of carcass weight increase on meat quality and sensory properties of pork loin. J Anim Sci Technol. 2020; 62:753-60

45.

Hoa VB, Seo HW, Seong PN, Cho SH, Kang SM, Kim YS, et al. Back-fat thickness as a primary index reflecting the yield and overall acceptance of pork meat. Anim Sci J. 2021; 92e13515