## 4 Discussion
The pH measured 24 h after slaughter is an important measurement because it can influence several attributes of meat quality [33; 34]. Meat pH can vary depending on many factors [34; 39]. The greater SFT observed in bulls finished in the FELOT and PRIME systems may be related to the energy supply during the rearing and finishing period of the bulls. It is worth noting that for all systems, the SFT was above the recommended level to classify a carcass as well finished by the Brazilian system (from 3.0 to 6.0 mm). The SFT is higher in bulls finished with high-energy density rations compared to animals finished on pasture [8]. SFT is highly correlated with dietary energy levels and is an indicator of good finishing. SFT plays a fundamental role in the post-slaughter period by protecting the carcass during chilling and preventing shortening due to cold [40]. In general, crossbred bulls finished in feedlot with a carcass weight of 250 to 270 kg have an LYA close to 85 cm\({}^{2}\)[15; 25; 32]. In any case, on average, the _Longissimus dorsi_ area was above 100 cm\({}^{2}\) in all treatments; considered optimal for crossbred animals finished in feedlot. The degree of marbling classified as very good was similar for the three treatments (32.0%--PASTU, 34.0% FELOT and 32.0%--PRIME). The sum of marbling classified as good and very good was 70.0%--PASTU, 62.0%--FELOT and 80.0%--PRIME. Differences in the degree of marbling frequency can be attributed to the higher or lower nutrient density of the diets [11; 12]. The three rearing and finishing systems had no effect (\(p>0.05\)) on the percentage of muscle tissue measured in the sixth rib of bulls. The percentage of muscle tissue, on average across the three systems, was 62.35%. Crossbred bulls between _Bos taurus_ vs. _Bos indicius_ finished in a feedlot system have, on average, a percentage of muscle tissue in the sixth rib between 60 and 65% [10; 15; 25; 31; 41]. The percentage of fat on the sixth rib was lower in bulls from the PASTU system (18.5%) compared to the FELOT (21.4%) and PRIME (20.2%) systems. On the other hand, no difference was observed for animals from the FELOT and PRIME systems. The lower percentage of fat found in bulls from the PASTU system may be related to the lower energy intake during the pasture period because these do not provide the same energy content when compared to the feedlot. However, the percentages found in the PASTU system are close to the percentages of bulls slaughtered at close to 550 kg of body weight [10; 25; 32]. Unlike the percentage of adipose tissue, the percentage of bone tissue was higher in bulls from the PASTU system (18.3%) compared to the percentage of bulls from the FELOT (15.8%) and PRIME (16.9%) systems. The percentages of bone tissue in these last two systems were similar. The higher percentage of bone tissue in bulls in the PASTU system can be explained by the long period of time spent on extensive _Brachiaria_ pastures. The objective of this study was to evaluate a beef production system taking into account better sustainability of the system both from the point of view of production efficiency and respect for environmental adversities, such as avoiding burning of degraded pastures, aiding in the recovery of degraded systems, rationalizing deforestation, protecting groundwater, reducing the greenhouse effect, improving pasture quality with soil correction and precision fertilization techniques, among other current techniques [1, 42, 43, 44, 45]. Currently, beef bulls' production systems in Brazil face major challenges, so citizens of different stripes should be aware of the responsibilities of relevant policies, goals, and new strategies for beef production in tropical and subtropical regions [1, 2, 18, 43]. The greatest respect for the aforementioned aspects can be achieved through economic and social understandings, better understanding and respecting the economic sustainability policies of the production integration system [1, 6, 31, 45, 46].