## 4 Discussion
### Yield Grades  
The European classification system of beef focuses on the estimation of subcutaneous fat and muscling of the carcass. The question arose as to whether this system could be modified to improve classification of European carcasses. At German abattoirs, quantifying KPH-fat and rib-eye size is not part of the routine. Therefore, the parameters describing the yield grade of carcasses using VIA had to be modified and are, thus, not directly equivalent to the results obtained by the US approach. Furthermore, it must be considered that the absence of an accurate rib-eye cut, a necessity for the VIA assessment, hampered the assessment in the slaughter line. Carcasses assessed in the current study had similar carcass weights to those in recent studies with European beef breeds [28]. In contrast, variation of slaughter age was higher than in other studies [28; 29]. Although targeted for heterogeneity, the carcasses were randomly chosen in a commercial slaughterhouse and the results represent a typical sample of carcasses produced for the German beef market. Measured rib fat thickness varied widely between the different positions. Rib fat thickness measurements at the 12 th rib positions in the current study were slightly higher than in other studies on beef steers [30] and lower than on carcasses on Yearling bulls measured at the 12 th rib position. In contrast, rib fat at the 10 th rib position was lower than in a comparable study [30]. Weak correlations between the measured rib fat thickness at both positions highlighted the amount of variation/the variation of fat distribution in muscles, which corresponds with the results in other studies [16]. Calculated correlation coefficients showed positive trends between EUROP trade grade and the yield grade, but weak negative correlations between EUROP fat class and subcutaneous fat at both positions. In contrast, weaker positive relations for measured rib fat and EUROP fat class for bulls (r = 0.47), heifers (r = 0.5) and steers (r = 0.4) were found by [PERSON] et al. [12]. While a weak relationship between the graded fat class and the measured subcutaneous fat was expected, the results of the current study indicate that the measurement of subcutaneous fat thickness might replace subjective grading of the EUROP fat score. As rib fatness can be easily measured by VIA at the rib-eye positions, the implementation of VIA-measured rib fat in European classification systems would be useful in classifying carcasses in a more objective and reliable way. Correlations between measured subcutaneous fat at both rib positions were lower (r = 0.65) than correlations between marbling scores (r = 0.8), but highly significant. Considering its high precision and the reliable use of VIA as the gold standard in US grading systems, results of measured rib fat thickness may easily supplement the subjective EUROP grading system. However, this does not provide information for predicting the meat quality of carcasses [16]. The current study explored only a few traits that are included in US yield grading. Since the European classification contains different parameters to those used in other international beef grading schemes, a complete adoption of the American system is not necessary. Rather, it is a matter of integrating important parameters, such as marbling and rib fat, into the classification in order to supplement EUROP traits and enrich the information about qualitative aspects of carcasses used in processing and marketing strategies. Classifying the different quality levels may lead to an adapted distribution of carcassesaccording to the different requirements of the various markets, processors or consumers in the process line [31]. Considering the fact that other studies already emphasize the high accuracy of VIA in predicting carcass traits [20; 21; 22], the implementation of VIA in European classification systems is highly recommendable, if not essential.