摘要
A divergent selection experiment using feed:gain ratios as the selection criterion was conducted in the early 1980s using Angus beef cattle located at the Eastern Agricultural Research Station (EARS), Belle Valley, OH. Numbers of bulls completing the 140-d postweaning performance test in 1979 through 1983 were 35, 34, 35, 34, and 33, respectively. Each year, the 3 bulls with the highest feed:gain ratios and the 3 bulls with the lowest feed:gain ratios were selected from the individually fed bulls, and were randomly mated as 2-yr-olds to approximately 20 cows each in a test herd of Angus cows also located at EARS. The progeny of these matings were then fed to assess postweaning and carcass performance. The objective of the current study was to compare the results of the experiment based on divergent selection for feed:gain ratios with those that would have been obtained using residual feed intake (RFI) as the selection criterion. RFI was calculated using 3 approaches: (1) dry matter intake (DMI) adjusted for production (i.e., ADG and metabolic midweight) to derive RFIP; (2) DMI adjusted for ultrasonic backfat thickness at the end of the 140-d test, in addition to ADG and metabolic midweight, to obtain RFIBF; and (3) DMI estimated using the NRC net energy equations, taking into account the energy and feed required for both gain and maintenance, to derive RFINRC. RFI was calculated by subtracting expected feed intake, derived using these 3 approaches, from the observed feed intake. Low RFIP and RFIBF bulls consumed less feed than high RFI bulls, whereas no differences existed for weight traits or ADG. Both feed:gain ratio and RFINRC were significantly correlated with weight traits and ADG on a phenotypic basis. The correlation between RFIP and RFIBF was near 1.0. In addition, rankings of the bulls were very similar based on RFIP and RFIBF. However, RFIBF may be the best selection criterion for feed efficiency examined in this study, as it was phenotypically independent of backfat thickness, in addition to weights and gains, and, therefore, would be less likely to negatively impact marbling score and carcass quality grade.
摘要译文
使用饲料：增重率作为选择标准的分歧选择实验在20世纪80年代初期使用位于东部农业研究站（EARS）的安格斯肉牛进行，美国俄亥俄州贝尔谷。从1979年到1983年完成140天断奶后性能测试的公牛数分别为35,34,35,34和33。每年，从单独喂养的公牛中选择具有最高饲料收益率的3头公牛和具有最低饲料：收益率的3头公牛，并随机交配为2岁龄至每头约20只奶牛，这些奶牛也位于EARS的安格斯奶牛试验群。然后喂食这些交配的后代以评估断奶后和胴体性能。tudy将比较实验的结果，该实验的结果基于饲料分歧选择：增加比例与使用残留饲料摄入量（RFI）作为选择标准获得的比例。使用3种方法计算RFI：（1）调整产量（即，ADG和代谢中等重量）的干物质摄入量（DMI）以得出RFI P;（2）除了ADG和代谢中等重量外，在140天试验结束时调整超声背thickness厚度的DMI以获得RFI BF;和（3）使用NRC净能量方程估计的DMI，同时考虑获取和维护所需的能量和饲料，以获得RFI NRC。通过使用这3种方法得出的预期采食量减去RFI，从观察到的采食量。低RFI P和RFI BF公牛比高RFI公牛消耗更少的饲料，而体重性状或ADG没有差异。在表型基础上，饲料：增重率和RFI NRC均与体重性状和ADG显着相关。 RFI P和RFI BF之间的相关性接近1.0。此外，根据RFI P和RFI BF，公牛的排名非常相似。然而，RFI BF可能是本研究中检验的饲料效率的最佳选择标准，因为它在表型上与背thickness厚度无关，除了重量和收益之外，因此不太可能负面影响大理石花纹得分和胴体品质等级。
S.N.Smith;M.E.Davis;S.C.Loerch;. Residual feed intake of Angus beef cattle divergently selected for feed conversion ratio[J]. Livestock Science, 2010,132(1-3): 41-47