J. Anim Sci. 2006. 84:3204-3211. doi:10.2527/jas.2005-610
© 2006 American Society of Animal Science
Effect of carcass price fluctuations on genetic and economic evaluation of carcass traits in Japanese Black cattle1
T. Ibi*,2,
A. K. Kahi
and
H. Hirooka
* Department of Animal Research, Agura Farm, Nasushiobara, 325-0033, Japan and
and
Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto, 606-8502, Japan
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Abstract
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The objectives of this study were 1) to investigate the effect of changes in carcass market prices due to bovine spongiform encephalopathy (BSE) occurrences on estimates of genetic parameters and economic weights for carcass traits; and 2) to compare direct and indirect approaches for prediction of genetic merit of Japanese Black cattle for profitability of their progeny. The direct approach utilized estimated breeding values of carcass prices, whereas in the indirect approach, selection indices were constructed as products of economic weights and breeding values of component traits. Data were composed of 80,191 carcass records divided into 5 periods based on changes in carcass prices as a result of occurrences of BSE in Japan and the United States. The periods ranged from a period before occurrence of BSE in Japan to a period of beef import restrictions and a rise in prices. Carcass traits analyzed included HCW, LM area, rib thickness, subcutaneous fat thickness, and marbling score (MS). Price traits included carcass unit price and carcass sale price. Estimates of heritability for price traits were moderate (0.32 to 0.46) and slightly sensitive to changes in carcass market prices. Genetic correlations of HCW and LM area with price traits increased and that between MS and carcass sale price decreased with period, whereas estimates of genetic correlation between MS and carcass unit price were high in all periods (0.96 to 0.98). Economic weights for carcass traits varied with periods because carcass prices were highly sensitive to economic importance of traits. Nevertheless, correlations between within-period breeding values for price traits estimated using direct and indirect approaches were high (0.92 to 0.99). This result indicates that selection realized by direct and indirect approaches will provide very similar results. A comparison among within-approach breeding values estimated in different periods showed that the largest differences in breeding values of sires for price traits were between the periods after occurrences of BSE in Japan and in the United States. Economic effects of BSE occurrences influenced the importance of carcass traits and economic merits of price traits through a change of carcass prices from period to period, irrespective of the approach taken in determining the genetic merit of breeding animals for profitability of their progeny.
Key Words: bovine spongiform encephalopathy • carcass price • economic weight • genetic parameter
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INTRODUCTION
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Carcass traits in beef cattle are important determinants of meat quality. In Japan, genetic parameters for carcass traits have been estimated for the Japanese beef cattle (i.e., Wagyu; Mukai et al., 1995
; Hirooka and Matsumoto, 1996; Oikawa et al., 2000; Ibi et al., 2005). Traditionally, selection index or multiple trait BLUP methods have been applied to estimate breeding values of multiple traits and to predict the aggregate genotypes. Economic weights are used to combine the estimated breeding values for the component traits into an estimated breeding value for aggregate genotype for selection purposes. This approach (so-called indirect approach), although very useful, assumes that genetic parameters for all traits are known and may be affected by nonlinear relationships between traits.
Visscher and Goddard (1995) and Pérez-Cabal and Alenda (2003) proposed an alternative approach (so-called direct approach) that deals with prediction of profit breeding value considering profit as a trait for evaluation, when information on profit is available on individual animals. The direct approach requires few genetic parameters and implicitly considers nonlinear relationships between traits. However, profit of animals may vary with economic situations. Similarly, economic weights in the indirect approach may also differ with economic situations. It is therefore important to investigate the robustness of both approaches considering various economic situations.
Identification of the first cows infected with bovine spongiform encephalopathy (BSE) in September 2001 in Japan, and in December 2003 in the United States, had a strong effect on carcass market prices in Japan. The objectives of this study were to investigate genetic and economic evaluation of carcass traits under various economic situations as affected by BSE occurrences and to compare direct and indirect approaches for prediction of genetic merit of Japanese Black cattle for profitability of their progeny.
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MATERIALS AND METHODS
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Animal Care and Use Committee approval was not obtained for this study because the data were obtained from an existing database.
Data were collected from farms consigned under the Agura Farm enterprise, which is the largest cooperative farming company raising Japanese Black cattle in Japan. The management system for Japanese Black cattle was described in a previous manuscript (Ibi et al., 2005). The original data consisted of 80,191 carcass and price records collected from April 1999 to March 2005. The carcass traits analyzed included HCW, LM area (LMA), rib thickness (RT), subcutaneous fat thickness (SFT), and marbling score (MS). Measurements of LMA, RT, SFT, and MS were at the sixth- to seventh-rib section.
The LMA was measured on the left side of the carcass by grid approximation [i.e., by placing a transparent sheet with grids (1 cm x 1 cm) on a section and counting the number of intersections with the LM]. The RT was the distance between the latissimus dorsi muscle and the pleura membrane measured halfway between the rib ends. The MS was measured according to the Beef Marbling Standard, with scores of 1 to 12 (a so-called BMS number), with 12 indicating the greatest amount of intramuscular fat and being the most favorable in Japan (JMGA, 1988).
The price traits analyzed were 2 types of carcass prices, namely carcass unit price (CUP) and carcass sale price (CSP). Carcass sale price was calculated as the product of HCW and CUP. In Japan, CUP was decided by buyers at auction for each carcass and reflected quality of the carcass. Therefore, CUP was affected by economic conditions. The CSP is more important to the farmers because a greater price for the carcass directly translates to more income for them.
Figure 1 illustrates the effects of occurrences of BSE in Japan and the United States on CUP. In September 2001, the first case of BSE was reported in Japan, and as a result, CUP declined rapidly because BSE had been linked to the fatal variant Creutzfeldt-Jacob disease in humans. The Japanese government introduced 2 systems to protect consumers from BSE and to guard against further decline in beef prices due to a rapid decrease in demand for beef. These included the new BSE control system, which ensures that all cattle are tested for BSE before slaughter and the traceability system, which traces all animals from birth to harvest. Consequently, the prices recovered to the level they were before the occurrence of BSE. In December 2003, the first case of BSE was reported in the United States. As a result, the Japanese Government banned US beef imports. This affected the supply of beef in Japan and resulted in a further increase in prices.
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Figure 1. Trend in carcass unit price (Yen/kg) as a result of bovine spongiform encephalopathy (BSE) occurrence and period from April 1999 to March 2005. Period A = period before occurrence of BSE in Japan (April 1999 to August 2001); period B = period of rapid decline in prices after occurrence of BSE (September 2001 to February 2002); period C = period of recovery of prices (March 2002 to August 2002); period D = period prior to occurrence of BSE in United States (September 2002 to December 2003); and period E = period of further rise in prices (January 2004 to March 2005).
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In this study, the original data were divided into the following 5 periods (Figure 1
); the period before the occurrence of BSE in Japan (April 1999 to August 2001; period A); the period of rapid decline in prices after the occurrence of BSE (September 2001 to February 2002; period B); the period of recovery of prices (March 2002 to August 2002; period C); the period before the occurrence of BSE in the United States (September 2002 to December 2003; period D); the period of beef import restrictions and further rise in prices (January 2004 to March 2005; period E). This study assumed that the populations of cattle in the different periods were independent. This ensured the determination of the effects of carcass prices on economic and genetic evaluation under considerably different carcass prices due to BSE occurrences in Japan and the United States.
Only records from carcass markets and farms having more than 25 records within each period were used in this analysis. Pedigree information was traced back 2 generations. As a result, the number of animals included in the analysis was 54,758, 18,071, 26,193, 54,768, and 54,919 in periods A, B, C, D, and E, respectively. Table 1 shows the number of records, feedlot farms, carcass markets, and sires used in each period. The following animal model, which included all relationships among all animals, was used to estimate genetic parameters and breeding values for carcass and price traits in each period:
 | [1] |
where yijklmn is observation ijklmn for a carcass or price trait; µ is the population mean; ai is the random effect of animal i; SEXj is the fixed effect of sex j; FARMk is the fixed effect of fattening farm k; CMl is the fixed effect of carcass market l; YMm is the fixed effect of combination of slaughter year and month m; AGEijklmn is slaughter age in days for observation ijklmn; FPijklmn is feedlot period (i.e., length of time spent in the feedlot) in days for observation ijklmn; b1 and b2 are linear and quadratic partial regression coefficients, respectively, for the regression of dependent variables on slaughter age; b3 and b4 are linear and quadratic partial regression coefficients, respectively, for the regression of dependent variables on length of the feedlot period; and eijklmn is the random residual associated with observation ijklmn.
Genetic parameters were estimated using MTDFREML programs (Boldman et al., 1993). Convergence was considered to have been reached when the variance of the –2 log likelihoods in the simplex was less than 10–4. After initial convergence, cold restarts were terminated when the variance of the –2 log likelihoods in the simplex fell below 10–8. Estimated genetic parameters were used to estimate breeding values of carcass and price traits. Standard errors for heritability and genetic correlation estimates were approximated using the formula provided by Koots (1994).
Breeding values for price traits were estimated directly and indirectly. In the direct approach, the breeding values estimated for price traits from Eq. 1 were adopted. In the indirect approach, a selection index was used to indirectly predict breeding values of price traits, and thus, economic weights were required to establish the selection index. The economic weights were obtained as partial regression coefficients of breeding values of price traits on breeding values of carcass traits using a multiple regression model in SAS (SAS Inst. Inc., Cary, NC), as follows:
 | [2] |
where H is a vector of estimated breeding values of price traits for individual animals; a is a vector of economic weights for each carcass trait; and gBLUPC is a vector of estimated breeding values for each carcass trait in individual animals. In this approach, breeding values of price traits are regarded as aggregate genotypes.
Hazel (1943) first defined economic weights of a trait as the net increase in aggregate genotype (ordinary profit) as a result of a unit change in 1 trait, independent of effects from genetic changes in other traits. Economic weights were estimated from relationships between the estimated breeding value of profit and breeding values of component traits because the independent and dependent variables (traits) are genetic values (Hazel, 1943). Standardized economic weights were also estimated by multiplying the economic weight of each carcass trait by its respective genetic standard deviation. These standard economic weights provide opportunity for comparisons of the relative importance of different traits in the breeding objective.
To compare selection criteria when direct or indirect approaches were applied, correlation coefficients between estimated breeding values of sires for price traits were estimated. The number of sires used in this analysis was 58. These were sires whose accuracy of estimated breeding values was greater than 80% across all periods. In this case, correlations between within-period breeding values estimated using both direct and indirect approaches and between within-approach estimated breeding values obtained using either direct or indirect approaches in the different periods were obtained.
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RESULTS AND DISCUSSION
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Table 2 shows basic statistics for carcass and price traits and management variables (feedlot period and slaughter age) by period. After occurrence of BSE in Japan, the feedlot period increased from 692 d (period A) to 731 d (period C), resulting in older slaughter ages (952 d in period A to 1,000 d in period C) and consequently heavier carcasses (397 kg in period A to 422 kg in period C). This trend was probably due to the decline in demand for beef. Consequently, farmers could not sell animals at carcass markets, resulting in long feedlot periods. Since the recovery of beef prices, the tendency has been toward keeping animals for a longer period in feedlots so that they later fetch more income as a result of having heavier HCW.
Table 3 shows estimates of heritability for carcass and price traits by period. Furthermore, heritabilities for these traits were also estimated using the entire data set. These were 0.43, 0.42, 0.47, 0.37, 0.33, 0.52, and 0.54 for CSP, CUP, HCW, LMA, RT, SFT, and MS, respectively. Estimates of heritability for carcass traits were in agreement with literature values for Japanese Black cattle (Mukai et al., 1995; Oikawa et al., 2000; Kawada et al., 2003). The heritabilities estimated for price traits were lower in periods B and C than in the other periods. In general, estimates of heritability for price traits were moderate (0.32 to 0.46) and slightly sensitive to changes in carcass market prices due to BSE occurrences. Hirooka and Matsumoto (1996) reported a heritability estimate of 0.49 for CUP in Japanese Brown cattle, which is slightly higher than the estimates in the current study.
Estimates of genetic correlation between carcass and price traits in each period are shown in Table 4. In most cases, the genetic correlations between carcass and price traits in period B were different from those obtained in the other periods. In period B, the genetic correlations of HCW and RT with price traits were much lower than in other periods, whereas those between SFT and price traits were negative. This result could be a consequence of a dramatic decline in carcass price in period B. In contrast, the genetic correlation between MS and CSP was relatively higher in this period than in the others. This result may be attributed to the strong influence of marbling on carcass prices, especially when the demand for beef was low. Apart from period B, the genetic correlation of HCW and LMA with price traits increased and that between MS and CSP decreased with period. Estimates of genetic correlation between MS and CUP were high in all periods (0.96 to 0.98).
Shown in Table 5 are economic weights and standardized economic weights for carcass traits used to estimate aggregate genotypes. Economic weights and standardized economic weights for carcass traits varied with period, indicating high sensitivity of economic weights to change in carcass prices. Among carcass traits, MS had the highest economic weight, consistent with other studies in Japan (Hirooka and Matsumoto, 1996; Hirooka and Sasaki, 1998). Economic weight of MS based on CSP decreased with period. The decline was largest after period D. Economic weight for HCW based on CSP was positive and increased from period B through period E. Standardized economic weights for HCW and MS based on CSP were high in all periods. For MS, the highest standardized economic weights were in periods A and B. After period B, standardized economic weights of MS decreased, whereas those of HCW increased with period. In period E, standardized economic weight of HCW was higher than that of MS. These findings may be a result of the small price difference between high and low marbled beef. This small difference in prices was brought about by the ban of beef imports from the United States following recovery of beef consumption and price (after period D), which led to a shortage in supply of domestic beef. Consequently, even low quality beef was purchased at relatively high prices.
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Table 5. Economic weights and standardized economic weights for carcass traits1 estimated based on each of the price traits in each period
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The importance of MS and HCW to CSP was very large. The importance of carcass traits to CSP across periods was variable. For example, MS was consistently more important than SFT to CSP across all periods, but this difference was markedly greater in period A relative to any of the subsequent periods. The economic weights and standardized economic weights for SFT based on CSP were negative. This is contrary to Hirooka and Sasaki (1998) who reported positive economic weights for SFT based on CSP. This difference probably was a result of the time periods in which the data were collected. Hirooka and Sasaki (1998) used data that were collected from 1988 to 1990, before the trade liberalization of the beef market in 1991. Economic weights for HCW based on CUP were negative in period B and later. This indicates that heavy carcasses were avoided and traded at lower prices in carcass markets after BSE occurrence in Japan. This was because of the perception of Japanese consumers who associated heavy carcasses with old animals and hence with BSE infection because the first case of BSE was reported in an old dairy cow. Standardized economic weights for MS based on CUP decreased with period and were lowest in period E. For all traits, the pattern in economic weights and standardized economic weights for carcass traits was similar. For example, the economic weights and standardized economic weights for HCW based on CUP were negative in period B and thereafter, whereas they were negative throughout all periods for SFT. Hirooka and Sasaki (1998) also reported a negative economic weight for SFT based on CUP.
Standardized economic weights provide opportunity for comparison of the relative importance of different traits as components of the breeding objective. In this study, the standardized economic weights for the different traits were variable as a result of the perception of consumers and may not reflect relative economic importance of the traits. Improving HCW is important in any beef production enterprise given its direct relationship with profitability. However, the standardized economic weights for HCW based on CUP were positive in period A and negative in period B and later. Apart from SFT, other carcass traits had positive economic values in all periods, indicating that an increment in any one of the traits would consistently lead to increased CSP and CUP. Positive economic values for SFT are undesirable because animals with thicker subcutaneous fat may have heavier carcasses, which would mistakenly translate into higher CSP and hence profitability.
Table 6 shows correlations between within-period breeding values for price traits estimated using both direct and indirect approaches and between within-approach breeding values estimated using either direct or indirect approaches in the different periods. Correlations between within-period breeding values for price traits estimated using both direct and indirect approaches were high and ranged from 0.92 to 0.99. This finding indicates that selection using direct and indirect predictions will provide similar results. Pérez-Cabal and Alenda (2003) reported lower correlations that ranged from 0.46 to 0.49 between direct and indirect predictions for lifetime profit in dairy cows. Pérez-Cabal and Alenda (2003) pointed out that breeding value of profit predicted directly provided better and more useful predictions of genetic merit of profit because few genetic parameters were necessary for analysis. Goddard (1998) concluded that use of profit directly as a trait is a better criterion for selection when there are complex relationships between traits involved in the profit function.
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Table 6. Correlations between within-period breeding values of sires for price traits estimated using both direct and indirect approaches (on diagonal) and between within-approach breeding values estimated using either direct (above diagonal) or indirect (below diagonal) approaches in the different periods
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Correlations between within-approach breeding values estimated using either direct or indirect approaches in the different periods ranged from 0.64 to 0.91 for CSP and 0.73 to 0.88 for CUP (Table 6). In particular, the correlations between periods B and E were lowest in all cases. This indicates that the largest differences in breeding values of sires for price traits were found between the periods after occurrences of BSE in Japan (period B) and in the United States (period E). Economic impacts of BSE occurrences influenced economic merits of price traits irrespective of the approach taken in determining the genetic merit of breeding animals for profitability of their progeny.
The choice of traits, price or profit, to be the aggregate genotype is challenging given the uniqueness of production systems. In this study, price traits were used as aggregate genotypes in the direct approach. In general, profit traits have been adopted as aggregate genotypes in dairy cattle (Visscher and Goddard, 1995; Pérez-Cabal and Alenda, 2003). However, price traits have also been used as aggregate genotypes. Hovenier et al. (1993) and von Rohr et al. (1999) estimated economic weights for meat quality traits in pigs using marginal income (revenue) functions instead of profit functions. Hirooka and Sasaki (1998) argued that when carcass quality traits are evaluated, use of breeding objectives utilizing economic weights estimated based on output variables (i.e., carcass price) is justified because importance of such traits may not be much affected by input variables such as feed and labor costs. Actually, most farmers in Japan are interested in revenue rather than profit. In addition, it is very difficult to collect records on input variables for beef cattle under field conditions.
In this study, all traits were adjusted for slaughter age in each period, and therefore, genetic parameters and economic weights are regarded as age-constant parameters. Ríos-Utrera et al. (2005) pointed out that biological differences exist among different endpoints (i.e., age, carcass weight, or fat thickness), and variation in weight of carcass components reflects variation in their growth rates when age is taken as an end point. Lee et al. (2000), Shanks et al. (2001), and Ríos-Utrera et al. (2005) reported different estimates of genetic parameters of carcass traits for different endpoints. Wilton and Goddard (1996) showed the possibility of changes in economic weights for different endpoints but proved that equivalent economic weights can be obtained regardless of end point if management variables are optimized for the current genotype. In beef production systems in Japan, age is the primary criterion that determines slaughter date.
Derivation of economic weights in this study did not consider nonlinear relationships among traits. Consequently, when breeding objective functions (ordinary profit functions) are actually nonlinear, linearization of the functions may result in bias of derived economic weights. Hovenier et al. (1993) and von Rohr et al. (1999) reported nonlinear relationships among meat quality traits in pigs. The economic weights of such traits may depend on the level of the trait itself or on the level of other traits. Nevertheless, Goddard (1983) first noted that a linear selection index will always be optimal, even if nonlinear relationships among traits are assumed. It should be emphasized that the direct approach shown in this study considered nonlinear relationships between carcass traits.
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IMPLICATIONS
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Occurrence of bovine spongiform encephalopathy in Japan and United States had large economic effects on consumption and price of beef in Japan. The impacts on carcass price resulted in different estimates of genetic parameters and economic weights for important traits that determine profitability in a beef production enterprise in Japan. Effect of beef marbling on carcass price was very large, but effects became smaller with time. Correlations between within-period breeding values for price traits estimated using direct and indirect approaches were high. Carcass unit price and carcass sale price are routinely recorded in Japan. Therefore, breeding values of price traits predicted directly would be useful in determining the genetic merit of breeding animals for profitability of their progeny. The usefulness of selecting for price traits depends entirely on the pricing system remaining constant.
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Footnotes
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1 These field data were collected by staff of the Agura Farm. Their help is gratefully acknowledged. 
2 Corresponding author: ibi-agr{at}rmail.plala.or.jp
Received for publication October 21, 2005.
Accepted for publication June 1, 2006.
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Abstract
INTRODUCTION
