The hypothesis that inclusion of a rumen-inert fat in the diet of dairy-origin bulls would enhance EUROP carcass fat classification and tissue fatty acid composition was tested. Sixty bulls (age = 508 days, s.d. 29.1) were offered ad libitum, a barley-based concentrate ration that contained 0, (control) 26 (MEGA1) or 81 g (MEGA2) calcium salts of palm oil fatty acids (Megalac)/kg such that the rations contained 25, 49 and 116 g acid-hydrolysed ether extract /kg dry matter (DM), respectively. Intake (per pen of 5 bulls), live weight and ultrasonic backfat thickness were measured during a 130 day feeding period after which bulls were slaughtered, carcass characteristics recorded and a sample of longissimus muscle (LT) and subcutaneous adipose tissue (SAT) collected for fatty acid analysis. Subcutaneous fat depth was similar for control and MEGA1 bulls but lower (P < 0.05) for MEGA2 bulls after 60 days of the study. After 125 days, compared to control bulls subcutaneous fat depth was higher for MEGA1 bulls but lower for MEGA 2 bulls (P < 0.05). Carcass gain tended (P = 0.074) to be lower for MEGA2 bulls compared to control and MEGA1 bulls, which reflected their lower consumption of concentrate DM and metabolisable energy (ME) but the efficiency with which consumed DM or ME was converted to live or carcass weight did not differ significantly between rations. There was no difference between control and MEGA1 bulls for any measurement of carcass fatness. Compared to control and MEGA1 bulls, carcasses from MEGA2 bulls were lighter, had a lower depth of fat covering the LT muscle measured post-mortem (P < 0.05) and a numerically lower carcass fat classification. There were only minor effects of ration composition on the fatty acid profile of LT or SAT. With regard to nutritional indices in meat, compared to control bulls, inclusion of Megalac did not affect the polyunsaturated (P) to saturated fatty acid ratio or the n-6 to n-3 P ratio of tissue lipids. It is concluded that for the type of animal and feeding arrangement in this study, rumen inert fat inclusion was not an effective strategy to enhance carcass fat classification or the nutritional value of beef.

检验了在产奶公牛的饮食中添加瘤胃惰性脂肪会增强EUROP car体脂肪分类和组织脂肪酸组成的假说。随意提供60头公牛（年龄= 508天，sd 29.1），这是一种大麦基浓缩饲料，其中含有0，（对照）26（MEGA1）或81 g（MEGA2）棕榈油脂肪酸（Megalac）的钙盐/因此，这些口粮分别含有25、49和116 g酸水解的醚提取物/ kg干物质（DM）。在130天的饲喂期中测量了进食量（每只5头公牛），活重和超声背脂厚度，之后屠宰了公牛，记录了cas体特征并记录了一个长牛的样本收集肌肉（LT）和皮下脂肪组织（SAT）进行脂肪酸分析。对照和MEGA1公牛的皮下脂肪深度相似，但研究60天后MEGA2公牛的皮下脂肪深度较低（P <0.05）。125天后，与对照公牛相比，MEGA1公牛的皮下脂肪深度更高，而MEGA 2公牛的皮下脂肪深度更低（P <0.05）。胴体增益倾向于（P = 0.074）比对照和MEGA1多头的公牛要低，这反映出他们降低了精料DM和代谢能（ME）的消耗量，但将消耗的DM或ME转化为活体或car体重量的效率没有显着差异在口粮之间。对于any体脂肪的任何测量，对照组和MEGA1公牛之间没有差异。与对照组和MEGA1公牛相比，MEGA2公牛的尸体重量较轻，死后测得的覆盖LT肌肉的脂肪深度较低（P<0.05）和较低的car体脂肪分类数值。日粮组成对LT或SAT脂肪酸谱的影响很小。关于肉类的营养指标，与对照公牛相比，加入Megalac不会影响组织脂质的多不饱和（P）与饱和脂肪酸之比或n-6与n-3 P之比。结论是，对于本研究中的动物类型和饲喂安排，瘤胃惰性脂肪夹杂不是提高enhance体脂肪分类或牛肉营养价值的有效策略。