| This research was divided into three parts, attempted to solve the following problems: firstly, to obtain the prime nutrition level of diets that was suitable to beef cattle fattening; secondly, effects of different nutrition levels on slaughtering performance, prime cuts yield and beef quality; finally, the relationship between different nutrition levels and economic utility of different growth phasis, and the economic effect of Beef Grading Technology on prime beef carcass.24 crossbred beef catties were divided into three groups ad libitum, in each group, the average weight was about 318kg (P>0.05), while the average age was about 1.5years (P>0.05). Three groups were feed low, middle and high nutrition level of diets respectively for 240 days. The fattening trial showed that beef cattle weight and average daily gain positive correlated with diets of different nutrition level. In the earlier stage of fattening, comparing with group I, final weight and average daily gain of group II and III had been improved 10.7%, 14.8% (P<0.01) and 82.8%, 118% respectively. Comparing with group II, daily gain of group III had been unproved 19.6% (P<0.05). In the later stage of fattening, comparing with group I, final weight and average daily gain of group III had been improved 28.3% and 90.2% respectively (P<0.01); while comparing with group I, final weight and average daily gain of group II had been improved 19.4% and 50.4% respectively (P<0.05). Nutrition level affected beef cattle productive performance and carcass quality significantly. Comparing with group I, indexes such as ante-mortem live weight, carcass weight, dressing percent, productive percent and meet-bone ratio of group II and III had extreme difference (P<0.01). Compared with group I, indexes such as ribeye area, backfat thickness and carcass fat of group III had difference (P<0.05). Ribeye area of group II, compare with group I, had difference (P<0.05), while backfat and carcass fat had the extreme difference (P<0.01). Nutrition level also affected prime cuts yield. Weight of each cut of group III had extreme difference (P<0.05) compared with group I. Compared with group I, gain weight of Tenderloin, Topside, Outside plat, Chuck tender and Brisket of group II had difference (P<0.05), while gain weight of Striploin, Ribeye, Eyeround, Rump, High rib, Knuckle and Shank of group II had extreme difference (P<0.01), which showed that weight of Striploin, Ribeye, Eyeround, Rump,High rib, Knuckle and Outside plat were more apt to be affected by diets than other cuts.In the trial of carcass performance and beef quality of three groups, it showed that, nutrition level did not affect beef carcass meat color and fat color, but affected some indexes (especially meat chemical composition) of beef quality. In total, the trend was that pH value, drip loss, boiling loss and shear force value of group I were partially high, while group II and III had no difference. Taste trials showed that nutrition level affected tenderness, juiciness, palatabiliry and integrate assement of Striploin differently. Indexes of Striploin of group III were higher than group I and II, but comparing with USDA Choice, there was no difference, and the juiciness was better than USDA Choice. Nutrition level did not affect indexes such as tenderness, juiciness and palatability of Tenderloin.Through economic utility analysis, we could see that nutrition level affected economic utility of each stage of beef cattle production. The result showed that the economic utility that could be acquired from group I, II and III were 13.1, 178.32, 322.02 yuan (RMB) respectively, which was different from each other. If the carcass of fattening cattle did not grade, the economic utility that could be acquired from group I, II and III were 472.28, 796.28 and 761.94 yuan, the difference between group I and group II, III were high, while group II and group III had no difference. For example, if we used grading technology on beef carcass Prime I of group III (high level of diets), according to "good beef, good... |
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