Influence of Increasing Carcass Weights on Pork Carcass Characteristics and Traditional and Alternative Fabrication Yields

Introduction

The average hot carcass weight (HCW) of U.S. pork has increased 17% from 82 kg to 97 kg from 1996 to 2022 (NASS, 2023). Using the current carcass weight increase rate of approximately 0.6 kg per year, the average pork carcass in the U.S. will be over 118 kg by 2050. This trend is projected to continue due to greater efficiency in pork production with increasing economies of scale. Increasing weights of pork carcasses creates the opportunity to reevaluate conventional U.S. pork fabrication specifications; however, alternative fabrication specifications and the resulting primal and subprimal weights from heavier pork carcasses have not been reported.

North American Meat Institute (formerly known as North American Meat Processors; NAMP) fabrication specifications are typically followed by U.S. pork processors with a shoulder-loin separation between the 2nd and 3rd rib to maximize loin and belly yields. Alternative fabrication methods used in other countries, including China, Japan, and South Korea, separate the shoulder and loin primals between the 4th and 5th rib. This change in fabrication increased gross carcass value (Bryan et al., 2018) even without changing carcass weights. Therefore, it is important to understand how altering fabrication methods in heavier carcasses would affect cut weights compared to current U.S. fabrication practices and average pork carcass weights. It is possible that, even with the reduction in loin and belly yield resulting from a change in fabrication method, increasing carcass weights would still result in adequate primal and cut weights.

In the current U.S. pork industry, individual muscles from the pork shoulder are not typically separated and merchandized because the added labor costs associated with their removal is not justified by the small cuts obtained. Additionally, the subsequent portion sizes from individual pork shoulder muscles would likely be too small to gain appeal and acceptance by customers. Instead, pork shoulders provide trim necessary for further processed products. However, as carcass weights increase, pork shoulders may have individual muscles that could be cut into adequate portion sizes similar to novel cuts created from the beef chuck including the top blade steak (NAMP 1114D), under blade steak (NAMP 1116G), and arm steak (NAMP 1114E).

Given the expectation that pork carcass weight will continue to increase, the objective of this study was to characterize the effects of increasing carcass weight on pork carcass characteristics and yields from traditional and alternative fabrication methods. Additionally, the weights of novel cuts from the shoulder from heavier carcasses were determined.

Materials and Methods

All protocols for the live portion of the experiment were reviewed and approved by the Institutional Animal Care and Use Committee at the University of Illinois (Protocol # 23045).

Results

The ELW of Very Heavy pigs was 18.6 kg heavier (P < 0.01) than Heavy pigs, which were approximately 20.3 kg heavier (P < 0.01) than Average pigs (Table 2). Subsequently, the HCW of Very Heavy carcasses was 16.7 kg heavier (P < 0.01) than Heavy carcasses, which was 17.2 kg heavier (P < 0.01) than Average carcasses. Carcass yield (dressing percentage) was increased (P < 0.01) in heavier carcasses compared with lighter carcasses. It should be noted that differences in slaughter procedure, such as having leaf fat weight included in HCW, resulted in higher carcass yields from these pigs compared with those expected from commercial processing. Loin muscle area was 5.5 cm² larger (P < 0.01) in Very Heavy carcasses compared with Heavy, which was 5.4 cm² larger (P < 0.01) than Average. Additionally, 10^th rib back fat depth in Very Heavy carcasses was about 0.3 cm greater (P < 0.01) compared with Heavy carcasses, which was about 0.4 cm greater (P < 0.01) than Average carcasses. Back fat depth of all carcasses ranged between 1.14 and 4.06 cm. Fat-free lean percentage was increased (P = 0.01) for Average carcasses (52.7%) compared with Heavy carcasses (51.5%) and Very Heavy carcasses (50.8%), which did not differ (P = 0.29) from each other.

Whole shoulders from alternative fabrication (4^th–5^th rib separation) were heavier (P < 0.01; Table 3) than shoulders from traditional fabrication (2^nd–3^rd rib separation). Regardless of fabrication method, absolute weight of whole shoulders increased with increasing carcass weight categories (P < 0.01). In traditional fabrication, the percentage of whole shoulder (expressed as a percentage of chilled side weight) was unchanged by carcass weight category. However, in alternative fabrication, percent whole shoulder was slightly increased (P < 0.01) for average weight carcasses compared with heavy and very heavy carcasses. Bone-in Boston butt weights increased with increasing carcass weight category (P < 0.01) and alternative fabrication (P < 0.01). Similar to the whole shoulder, minor differences in percent bone-in Boston were observed between carcass weight categories. Both bone-in and boneless picnic weight increased with increasing carcass weight category (P ≤ 0.01) and alternative fabrication (P ≤ 0.01). However, percent bone-in and boneless picnic were unchanged by carcass weight category (P ≥ 0.06). Minor cuts such as the jowl, neck bones, and clear plate all increased in weight with increasing carcass weight category (P ≤ 0.01) and alternative fabrication (P ≤ 0.01). Alternative fabrication also yielded additional cuts including the Boston cap muscle, a portion of the spinalis dorsi muscle, CT butt, supra- and infraspinatus, and SV from the Boston primal. All cuts fabricated from the Boston increased in weight along with carcass weight category (P ≤ 0.01). However, the percentage of these cuts, relative to side weight, was unchanged by carcass weight category (P ≥ 0.14). The teres major and TB were also further fabricated from the picnic. Similarly, the weight of the teres major and TB increased along with carcass weight category (P ≤ 0.01), but were unchanged by carcass weight category when expressed as a percentage of side weight (P ≥ 0.35).

No interactions were observed between carcass weight category and fabrication method for any loin primal or subprimal cuts (P ≥ 0.10; Table 4). Whole and trimmed loins from alternative fabrication were lighter than ones from traditional fabrication (P ≤ 0.01). Similarly, resulting cuts such as the Canadian back, backribs, and backbones were also lighter in weight from the alternative fabrication method (P ≤ 0.01). Absolute weight of whole and trimmed loins, as well as all resulting cuts, increased along with carcass weight category (P ≤ 0.01). Although minor differences in percent whole loin and Canadian back were observed between carcass weight categories (P ≤ 0.03), percent trimmed loin was unchanged by carcass weight category (P = 0.50). Tenderloin and sirloins increased in weight with increasing carcass weight categories but were unchanged by carcass weight category when expressed as a percentage of side weight (P ≥ 0.19). Tenderloin and sirloin were unchanged by fabrication method (P ≥ 0.22) whether expressed as absolute weights or as a percentage of side weight. No interactions were observed between carcass weight category and fabrication method for the belly primal or subprimal cut. Both whole bellies and spareribs from traditional fabrication were heavier and comprised a greater percentage of side weight than ones from alternative fabrication (P ≤ 0.01). Whole bellies and spareribs also increased in weight along carcass weight category. While whole belly percentage increased (P < 0.01) with carcass weight category, sparerib percentage decreased slightly (P < 0.01).

Ham primal and subprimal cut weights were averaged between whole and trimmed hams, as well as all subprimal cuts including the inside, outside, lite butt, knuckle, and inner shank, were heavier with increasing carcass weight category (P ≤ 0.01; Table 5). However, ham primal and subprimal cuts comprised a smaller percentage of side weight as carcass weight category increased (P ≤ 0.04).

The estimated value of each carcass was determined in a high pork prices and low pork prices scenario by multiplying the cutout weight of each primal by price per kg. The average price values for 2018–2019 were used in the low-price scenario (Figure 1) in which the traditional fabrication method was more profitable in each weight category. Traditional fabricated carcasses had an increased value of $2.03, $2.41, and $1.76 per side compared to sides alternatively fabricated in Average, Heavy, and Very Heavy carcasses, respectively. The average price values for 2021–2022 were used in the high price scenario (Figure 2). Traditional fabricated carcasses had an increased value of $2.82, $3.35, and $2.44 per side compared to sides alternatively fabricated in Average, Heavy, and Very Heavy carcasses, respectively.

Figure 1.

Figure 1.

Pork carcass side valuation with low average price (2018–2019) was determined as the sum of each primal value for each carcass weight class and each fabrication method. Traditional fabrication utilized a shoulder separation between the 2^nd/3^rd rib. Alternative fabrication utilized a shoulder separation between the 4^th/5^th rib. Values within a carcass weight category with differing superscripts are statistically different (P ≤ 0.05).

Figure 2.

Figure 2.

Pork carcass side valuation with high average price (2021–2022) was determined as the sum of each primal value for each carcass weight class and each fabrication method. Traditional fabrication utilized a shoulder separation between the 2^nd/3^rd rib. Alternative fabrication utilized a shoulder separation between the 4^th/5^th rib. Values within a carcass weight category with differing superscripts are statistically different (P ≤ 0.05).

Approximate value of each carcass was also determined in another pricing scenario considering different primal prices relative to each other. In pricing scenario 3, the value of each carcass was determined for a period where the price of loin and belly primals was considerably higher than shoulder primals. The average primal price values from February 2022 were used to represent a period where loin and belly primals were priced considerably higher than shoulder primals (Figure 3). In this scenario, traditional fabricated carcasses had an increased value of $3.82, $4.40, and $3.47 per side compared to sides alternatively fabricated in Average, Heavy, and Very Heavy carcasses, respectively. In pricing scenario 4, the value of each carcass was determined for a period where prices of shoulder primals were similar to loin and belly primals. The average primal price values from December 2022 were used to represent a period where loin and belly primals were similarly priced to shoulder primals (Figure 4). Traditional fabricated carcass sides had an increased value numerically compared to sides alternatively fabricated in all carcass weight categories. However, carcass value differences were small enough between traditional and alternative fabrication in the Average and Very Heavy carcass weight categories as to not be statistically different (P ≥ 0.18).

Figure 3.

Figure 3.

Pork carcass side valuation with high price differential between loin and belly vs. shoulder primals (4 wk average – February 2022) was determined as the sum of each primal value for each carcass weight class and each fabrication method. Traditional fabrication utilized a shoulder separation between the 2^nd/3^rd rib. Alternative fabrication utilized a shoulder separation between the 4^th/5^th rib. Values within a carcass weight category with differing superscripts are statistically different (P ≤ 0.05).

Figure 4.

Figure 4.

Pork carcass side valuation with low price differential between loin and belly vs. shoulder primals (4 wk average – December 2022) was determined as the sum of each primal value for each carcass weight class and each fabrication method. Traditional fabrication utilized a shoulder separation between the 2^nd/3^rd rib. Alternative fabrication utilized a shoulder separation between the 4^th/5^th rib. Values within a carcass weight category with differing superscripts are statistically different (P ≤ 0.05).

Discussion

Pork HCW have been increasing in the U.S. for more than 20 y and will likely continue to increase in the future due to improved economies of scale. Increasing carcass weights present a need to understand carcass yield with opportunity to reevaluate carcass fabrication specifications to create novel cuts for retail and food service.

Improved lean growth performance genetics have allowed for increased slaughter weights while maintaining carcass composition specifications. In a study evaluating commercial pigs up to 181 kg ELW, Shull (2013) observed limited effects on carcass leanness. Cisneros et al. (1996) reported that pigs with modern genetics could be slaughtered up to 160 kg ELW with limited impact to carcass yield. These results are similar to those reported in the current study. For every 1% increase in HCW, LMA increased by 0.64 percentage units in Heavy pigs. This increase was similar in Very Heavy pigs with every 1% increase in HCW corresponding to a 0.66 percentage unit increase in LMA. Furthermore, back fat depth increased 1.1 percentage units for every 1% increase in HCW for both Heavy and Very Heavy carcass weight categories. It is important to note similar rates of increase for both fat and lean measurements as carcass weight increased as excessive fatness at heavier carcass weights could be a concern.

Some concerns have been expressed that increasing carcass weight in pigs could result in issues similar to those currently observed in the broiler industry such as woody breast and white striping (Tijare et al., 2016; Kuttappan et al., 2016). Genetic selection for faster growth rate in chickens has resulted in unequal distribution of increased carcass weight heavily favoring increased breast weight (Petracci et al., 2015). Allometric (unequal) growth of the breast muscle relative to the rest of the carcass is likely one underlying cause of the current myopathies and poultry meat quality issues in the broiler industry (Kuttappan et al., 2016). Pigs in the current study did not reach heavier weights due to selection for increased weight of one primal compared with another. These findings may indicate that as carcasses get heavier, even up to 136 kg, myopathies like those observed in poultry are unlikely.

As expected, the absolute weights of primals and subprimal cuts increased as carcass weight increased. The 16.5% increase in HCW in Heavy compared to Average carcasses corresponded to an increase of primal weights by 14.2% in the shoulder, 17.4% in the loin, 20.0% in the belly, and 14.3% in the ham. The 32.4% increase in HCW in Very Heavy compared to Average carcasses corresponded to an increase of primal weights by 30.8% in the shoulder, 35.4% in the loin, 36.6% in the belly, and 27.0% in the ham. The trimmed ham as a percentage of chilled side decreased with carcass weight and was the least in Very Heavy carcasses. This was contrary to results of Wu et al. (2017), which observed general decreases in lean primal cut yields with increasing carcass size. However, in the present study, trimmed loin and boneless picnic yields were largely unchanged as carcass weights increased. This is likely due in part to different genetics as well as genetic improvements in lean yields at increased carcass weights. Alternatively, belly yield as a percentage of chilled side also increased slightly in heavier carcasses. This finding is in line with the Wu et al. (2017) review reporting belly primal yield generally increased with increasing weight. Although carcass weight was significant for some cut yields expressed as a percentage of chilled side weight, the magnitude of these differences were minimal. Findings of the present study support the view of approximately equal distribution of carcass weight throughout the entire carcass, highlighting the ability of pigs to be reared to increased weights while maintaining acceptable levels of leanness.

Alternative fabrication including a shoulder-loin separation between the 4th and 5th rib was explored. This fabrication method is utilized by several U.S. export countries, including China, Japan, South Korea, Argentina, Mexico, and Brazil. In 2022, the total U.S. pork export reached $7.7 billion, with Mexico, China, and Japan buying $4.9 billion (USMEF, 2022). Ray and Cravens (2002) highlighted the opportunity to further improve U.S. pork value by meeting export market needs including cutting specifications and improved fresh pork quality. However, moving to this alternative fabrication could be met with concern about decreased belly and loin yield compared to a traditional U.S. fabrication method. The alternative shoulder break did reduce loin and belly weights compared with traditional fabrication methods. Loin primal weight was reduced 11%–12% and the whole belly weight was reduced 7%–13% in alternatively fabricated carcasses compared to traditionally fabricated carcasses. However, given the anatomical location of reduced belly yield, the alternative shoulder break would not be expected to alter #1 bacon slices or those center-cut slices most valuable in retail packaging (Person et al., 2005). Furthermore, loin and belly primal weights from alternatively fabricated Heavy carcasses were heavier than traditionally fabricated Average carcasses. Therefore, increased carcass weights could present the opportunity to produce novel retail cuts from the shoulder without compromising loin and belly weights. In both the low total and high total price scenarios, traditional fabrication, regardless of weight category, provided increased carcass value largely due to the increased value of the loin and belly. Similarly, in a scenario where loin and belly prices were substantially higher than shoulder prices, carcass valuation would favor a traditional cutout. However, during a period where shoulder primal prices were similar to loin and belly prices, carcass valuation of a traditional and alternative 4^th/5^th rib fabrication were more similar. Therefore, processors could choose alternative fabrication methods under certain market conditions and gain more value from the fabrication of novel cuts. However, the limitation of this analysis is that primal prices used for all carcass valuation scenarios reflect primal value based on the value of traditional subprimal and retail cuts. The true value of a long-cut shoulder and a shortened loin or belly would be determined by the market and likely be different from prices of currently fabricated primals.

The SV and TB were removed from the alternatively fabricated pork shoulder as individual muscles for exploration as potential novel retail cuts. The weights of both the SV and TB were similar to the boneless sirloin, but the size and number of chops available from each respective muscle should be determined. Additionally, an attractive visual appearance and a high-quality eating experience would be imperative to justify merchandizing these cuts on their own. The SV and TB have been previously shown to have an ultimate pH of 6.26 and 6.10, respectively (Tavárez et al., 2012). As pH may influence pork quality traits including color water-holding capacity (Huff-Lonergan et al., 2002), determining whether or not expected improvements in quality of shoulder chops would translate to a more desirable eating experience would be the next step in developing these novel cuts as alternatives to traditional pork loin chops.

Conclusions

In conclusion, pork carcasses displayed proportional increasing lean and fat accretion with increasing carcass weight. Heavier pork carcasses yielded heavier cuts proportional to the increases in carcass weight. The alternative fabrication of pork shoulders reduced loin and belly length. However, loins and bellies from heavier carcasses weighed more than loins and bellies from carcasses commonly available in the U.S. industry today. Additionally, alternative fabrication of pork shoulders produced 2 muscles, the SV and TB, that warrant further exploration as novel retail cuts.