Relationship between body size traits and carcass traits with primal cuts yields in Hanwoo steers

Objective This study was conducted to evaluate the correlation between body size traits, carcass traits, and primal cuts in Hanwoo steers. Methods Sixty-one beef carcasses were classified for conformation and primal cut weight. Additionally, carcass weight, fat thickness, carcass dimensions, and longissimus muscle area were determined to complement the grading. Results The average live weight and cold carcass weight were 759 and 469 kg, respectively. The mean carcass meat, fat, and bone proportions were 551, 298, and 151 g/kg, respectively. Primal cuts weights showed significant positive correlations (p<0.001) of 0.42 to 0.82 with live weight, carcass weight, and longissimus muscle area and a significant negative correlation with carcass fat (without shank, −0.38 to −0.10). Primal cut weights were positively correlated (p<0.01) with carcass length (0.41 to 0.77), forequarter length (0.33 to 0.57), 6th lumbar vertebrae–heel length (0.33 to 0.59), 7th cervical vertebrae carcass breadth (0.35 to 0.58), 5th to 6th thoracic vertebrae breadth (0.36 to 0.65), 7th to 8th thoracic vertebrae girth (0.38 to 0.63), and coxae girth (0.34 to 0.56) and non-significantly related to cervical vertebrae length and coxae thickness. Conclusion There was a high correlation among live weight, carcass weight, longissimus muscle area, carcass length, 7th cervical vertebrae carcass breadth, 5th to 6th thoracic vertebrae breadth, and 7th to 8th thoracic vertebrae girth of the primal cuts yield. The correlation between fat and primal cut yields was highly significant and negative. Carcass length and 7th to 8th thoracic vertebrae girth, appear to be the most important traits affecting primal cut yields.


INTRODUCTION
Beef carcass grading systems are used to estimate the yield and determine the eating quality (palatability) of saleable meat. The meat industry in developed countries is showing trends toward marketing of individual muscle cuts to improve the value of retail meat cuts [1]. Both meat yield and distribution are the primary determinant of carcass value, which affect the value of meat cuts [2]. Studies have been conducted to examine the characteristics affecting carcass yield grade and retail product weight [3][4][5][6][7] and the retail product weight is mainly predicted based on the carcass weight (CW), longissimus dosi area, and carcass fat thickness (FT) [8][9][10]. A few studies have focused on the relationship between carcass scores and carcass composition values. The CW and carcass muscle score account for 38% of total variations in meat yield, with the carcass muscle score accounting for most of this value [11]. The CW alone, CW with carcass muscle score, and CW with carcass muscle and fat scores accounted for 0.1%, 37.9%, and 46.7%, respectively, of the total variation in saleable

Animal care
The animal use and protocols employed during the research were reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) at National Institute of Animal Science (approval number NIAS 20001992).

Animals and management
A total of 61 Hanwoo steers at 28 to 35 months of age was slaughtered at an abattoir of National Institute of Animal Science (Wanju, Korea). The slaughter of the cattle was carried out following the Guidelines of Animal Protection Law (Article 6) [15], and Livestock Sanitation Control Act Law (Annex 1) [16]. After chilling for 21 h at 1°C, the carcasses were weighed and dressing percentage was calculated.

Carcass characteristics
Abbreviations for the measurements collected in the study are provided in Table 1. The means and standard deviations for carcass traits are provided in Table 2 13.45±2.21 kg for shank, and 58.14 ±6.89 kg for ribs. The carcass characteristics and meat composition data were similar to those found in previous studies [18,19].

Correlation analyses: carcass traits
Simple correlations between carcass measurements and carcass primal product are presented in Table 3. As expected, the traits most strongly associated with primal cuts weight were LW, CW, and LMA. As CW increased, carcass dimensions and primal cut yields increased [6,[20][21][22]. Based on the values obtained for primal cuts, positive correlations were obtained using the CW with tenderloin proportion (r = 0.78), loin proportion (r = 0.78), strip lion proportion (r = 0.72), chuck roll proportion (r = 0.50), clod proportion (r = 0.72), top round proportion (r = 0.75), bottom round proportion (r = 0.76), brisket proportion (r = 0.76), shank proportion (r = 0.67), and ribs proportion (r = 0.64). Carcass FT showed a positive relationship (r = 0.04 to 0.39) with tenderloin, loin, strip lion, brisket, shank, and ribs but a negative relationship (r = -0.02 to -0.16) with chuck roll, clod, top round, and bottom round. FT was the most useful predictor of percent retail product from the major primal; however, an adjustment concerning the amount of fat in other locations was recommended [23]. Fat cover classification was negatively correlated with the conformation score classification and other muscular development traits such as the leg width and perimeter in both categories [24]. Other studies observed correlations between FT and carcass retail cut ranging from -0.52 to -0.73 [23,[25][26][27][28].
Positive correlations (p<0.001) were obtained between the LMA and tenderloin proportion (r = 0.54), loin proportion (r = 0.68), strip lion proportion (r = 0.73), chuck roll proportion (r = 0.42), clod proportion (r = 0.50), top round proportion (r = 0.59), bottom round proportion (r = 0.59), brisket proportion (r = 0.52), and ribs proportion (r = 0.55). Correlation coefficients between LMA and retail cut estimates reported previously showed r-values of 0.51 to 0.53 [20,29] and 0.62 to 0.70 [21,25,30,31]. The use of LMA to predict subprimal yield is controversial. Numerous studies have tested the usefulness of LMA for predicting cutability, which revealed a correlation between the ribeye area and both subprimal cut yields and major primal weights (r-values between 0.64 and 0.45) [21,23,32]. However, the USDA yield grade is not strongly influenced by LMA [33][34][35]. Using separable lean as a dependent variable, the loin eye area showed a low correlation with retail yield [36,37]. LMA exhibited a low but significant correlation with the percentage of retail product for the four primals but was not related to the weight of the retail product [6].

Correlation analyses: carcass size traits
Correlation coefficients (Table 3)   shank proportion (r = 0.52), and ribs proportion (r = 0.43). Positive correlations (p<0.001) were obtained between TVG (7th to 8th thoracic vertebrae girth) and the tenderloin proportion (r = 0.59), loin proportion (r = 0.63), strip lion proportion (r = 0.54), clod proportion (r = 0.52), top round proportion (r = 0.61), bottom round proportion (r = 0.61), brisket proportion (r = 0.61), shank proportion (r = 0.42), and ribs proportion (r = 0.62). Negative correlations were obtained for the chuck roll proportion with SVB (r = -0.16), LVT (r = -0.06), CT (r = -0.12), and TVT (r = -0.09). Correlations between the primal cut weight with CVL and CT were poor and generally not significant. The correlations between variables related to the leg volume, such as carcass width, leg depth, and leg perimeter, were highly significant for both commercial categories. However, the correlations among these muscle-related variables and those related to carcass size or skeletal size, such as CL and width between commercial categories [24]. The CL was positively related to the percentage of subprimal cuts from round and brisket, chuck, plate, and flank [38].

Development of a new prediction equation for determining
Hanwoo yield is required because of changes in the Korean beef industry; for example, the proportion of steers has dramatically increased, with slaughter weight of up to 760 kg. Our results showed that numerous variables in combination with body size or carcass traits can be used to more accurately estimate fat and carcass yields. There was a high correlation among LW, CW, LMA, CL, CVB, TVB, and TVG and primal cut yield. The correlation between fat and primal cut yields was highly negatively significant. The CL and TVG showed a high correlation with carcass yield. The relationship between carcass conformation and body size with carcass traits provides a basis for developing a carcass pricing structure that better reflects carcass value in terms of meat yield and distribution.

CONFLICT OF INTEREST
We certify that there is no conflict of interest with any financial organization regarding the material discussed in the manuscript. Sung-Sil Moon is an employee of Sunjin Meat Research Center.

ACKNOWLEDGMENTS
This study was supported by 2020 year Postdoctoral Fellowship Program (Project No. PJ01212501) of National Institute of Animal Science, Rural Development Administration, Republic of Korea.