Nkrumah J D, Basarab J A, Wang Z, Li C, Price M A, Okine E K, Crews D H, Moore S S
Igenity Livestock Production Business Unit, Merial Ltd., Edmonton, Alberta, T6G 2P5, Canada.
J Anim Sci. 2007 Oct;85(10):2711-20. doi: 10.2527/jas.2006-767. Epub 2007 May 25.
Feed intake and efficiency of growth are economically important traits of beef cattle. This study determined the relationships of daily DMI, feed:gain ratio [F:G, which is the reciprocal of the efficiency of gain (G:F) and therefore increases as the efficiency of gain decreases and vice versa, residual feed intake (RFI), and partial efficiency of growth (efficiency of ADG, PEG) with growth and carcass merit of beef cattle. Residual feed intake was calculated from phenotypic regression (RFIp) or genetic regression (RFIg) of ADG and metabolic BW on DMI. An F1 half-sib pedigree file containing 28 sires, 321 dams, and 464 progeny produced from crosses between Alberta Hybrid cows and Angus, Charolais, or Alberta Hybrid bulls was used. Families averaged 20 progeny per sire (range = 3 to 56). Performance, ultrasound, and DMI data was available on all progeny, of which 381 had carcass data. Phenotypic and genetic parameters were obtained using SAS and ASREML software, respectively. Differences in RFIp and RFIg, respectively, between the most and least efficient steers (i.e., steers with the lowest PEG) were 5.59 and 6.84 kg of DM/d. Heritabilities for DMI, F:G, PEG, RFIp, and RFIg were 0.54 +/- 0.15, 0.41 +/- 0.15, 0.56 +/- 0.16, 0.21 +/- 0.12, and 0.42 +/- 0.15, respectively. The genetic (r = 0.92) and phenotypic (r = 0.97) correlations between RFIp and RFIg indicated that the 2 indices are very similar. Both indices of RFI were favorably correlated phenotypically (P < 0.001) and genetically with DMI, F:G, and PEG. Residual feed intake was tendentiously genetically correlated with ADG (r = 0.46 +/- 0.45) and metabolic BW (r = 0.27 +/- 0.33), albeit with high SE. Genetically, RFIg was independent of ADG and BW but showed a phenotypic correlation with ADG (r = -0.21; P < 0.05). Daily DMI was correlated genetically (r = 0.28) and phenotypically (r = 0.30) with F:G. Both DMI and F:G were strongly correlated with ADG (r > 0.50), but only DMI had strong genetic (r = 0.87 +/- 0.10) and phenotypic (r = 0.65) correlations with metabolic BW. Generally, the phenotypic and genetic correlations of RFI with carcass merit were not different from zero, except genetic correlations of RFI with ultrasound and carcass LM area and carcass lean yield and phenotypic correlations of RFI with backfat thickness (P < 0.01). Daily DMI had moderate to high phenotypic (P < 0.01) and genetic correlations with all the ultrasound and carcass traits. Depending on how RFI technology is applied, adjustment for body composition in addition to growth may be required to minimize the potential for correlated responses to selection in cattle.
采食量和生长效率是肉牛重要的经济性状。本研究确定了肉牛的日干物质采食量（DMI）、饲料增重比[F:G，即增重效率（G:F）的倒数，因此随着增重效率降低而增加，反之亦然]、剩余采食量（RFI）以及生长部分效率（平均日增重效率，PEG）与肉牛生长和胴体品质之间的关系。剩余采食量通过DMI对平均日增重（ADG）和代谢体重的表型回归（RFIp）或遗传回归（RFIg）来计算。使用了一个F1半同胞系谱文件，该文件包含28头公牛、321头母牛以及由艾伯塔杂交母牛与安格斯、夏洛来或艾伯塔杂交公牛杂交产生的464头后代。每个公牛的家系平均有20头后代（范围 = 3至56头）。所有后代均有生产性能、超声检查和DMI数据，其中381头有胴体数据。分别使用SAS和ASREML软件获得表型和遗传参数。最高效和最低效阉牛（即PEG最低的阉牛）之间的RFIp和RFIg差异分别为5.59和6.84千克干物质/天。DMI、F:G、PEG、RFIp和RFIg的遗传力分别为0.54±0.15、0.41±0.15、0.56±0.16、0.21±0.12和0.42±0.15。RFIp和RFIg之间的遗传相关性（r = 0.92）和表型相关性（r = 0.97）表明这两个指标非常相似。RFI的两个指标在表型上（P < 0.001）和遗传上均与DMI、F:G和PEG呈正相关。剩余采食量与ADG（r = 水平）呈正相关。从遗传角度看，RFIg与ADG和体重无关，但与ADG呈表型相关性（r = -0.21；P < 0.05）。日DMI与F:G在遗传上（r = 0.28）和表型上（r = 0.30）呈相关。DMI和F:G均与ADG强烈相关（r > 0.50），但只有DMI与代谢体重有强烈的遗传相关性（r = 0.87±0.10）和表型相关性（r = 0.65）。一般来说，RFI与胴体品质的表型和遗传相关性与零无差异，但RFI与超声检查和胴体腰大肌面积、胴体瘦肉率的遗传相关性以及RFI与背膘厚度的表型相关性除外（P < 0.01）。日DMI与所有超声检查和胴体性状具有中度至高的表型相关性（P < 0.01）和遗传相关性。根据RFI技术的应用方式，可能需要除生长外对体组成进行调整，以尽量减少牛对选择的相关反应的可能性。
