Lancaster P A, Carstens G E, Ribeiro F R B, Tedeschi L O, Crews D H
Department of Animal Science, Oklahoma State University, Stillwater 74078, USA
J Anim Sci. 2009 Apr;87(4):1528-39. doi: 10.2527/jas.2008-1352. Epub 2008 Nov 7.
The objectives of this study were to characterize feed efficiency traits and to examine phenotypic correlations between performance and feeding behavior traits, and ultrasound measurements of carcass composition in growing bulls. Individual DMI and feeding behavior traits were measured in Angus bulls (n=341; initial BW=371.1+/-50.8 kg) fed a corn silage-based diet (ME=2.77 Mcal/kg of DM) for 84 d in trials 1 and 2 and for 70 d in trials 3 and 4 by using a GrowSafe feeding system. Meal duration (min/d) and meal frequency (events/d) were calculated for each bull from feeding behavior recorded by the GrowSafe system. Ultrasound measures of carcass 12th-rib fat thickness (BF) and LM area (LMA) were obtained at the start and end of each trial. Residual feed intake (RFIp) was computed from the linear regression of DMI on ADG and midtest BW(0.75) (metabolic BW, MBW), with trial, trial by ADG, and trial by midtest BW(0.75) as random effects (base model). Overall ADG, DMI, and RFIp were 1.44 (SD=0.29), 9.46 (SD=1.31), and 0.00 (SD=0.78) kg/d, respectively. Stepwise regression analysis revealed that inclusion of BW gain in BF and LMA in the base model increased R(2) (0.76 vs. 0.78) and accounted for 9% of the variation in DMI not explained by MBW and ADG (RFIp). Residual feed intake and carcass-adjusted residual feed intake (RFIc) were moderately correlated with DMI (0.60 and 0.55, respectively) and feed conversion ratio (FCR; 0.49 and 0.45, respectively), and strongly correlated with partial efficiency of growth (PEG; -0.84 and -0.78, respectively), but not with ADG or MBW. Gain in BF was weakly correlated with RFIp (0.30), FCR (-0.15), and PEG (-0.11), but not with RFIc. Gain in LMA was weakly correlated with RFIp (0.17) and FCR (-0.19), but not with PEG or RFIc. The Spearman rank correlation between RFIp and RFIc was high (0.91). Meal duration (0.41), head-down duration (0.38), and meal frequency (0.26) were correlated with RFIp and accounted for 35% of the variation in DMI not explained by MBW, ADG, and ultrasound traits (RFIc). These results suggest that adjusting residual feed intake for carcass composition will facilitate selection to reduce feed intake in cattle without affecting rate or composition of gain.
本研究的目的是对饲料效率性状进行特征描述，研究生长公牛的生产性能与采食行为性状之间的表型相关性，以及胴体组成的超声测量值。在试验1和试验2中，使用GrowSafe饲喂系统，对341头安格斯公牛（初始体重=371.1±50.8千克）饲喂以玉米青贮为基础的日粮（代谢能=2.77兆卡/千克干物质）84天；在试验3和试验4中饲喂70天，测量个体干物质采食量（DMI）和采食行为性状。根据GrowSafe系统记录的采食行为，计算每头公牛的采食持续时间（分钟/天）和采食频率（次数/天）。在每次试验开始和结束时，通过超声测量胴体第12肋处的脂肪厚度（BF）和腰大肌面积（LMA）。根据DMI对平均日增重（ADG）和试验中期体重（0.75次方）（代谢体重，MBW）的线性回归计算剩余采食量（RFIp），将试验、试验×ADG以及试验×试验中期体重（0.75次方）作为随机效应（基础模型）。总体ADG、DMI和RFIp分别为1.44（标准差=0.29）、9.46（标准差=1.31）和0.00（标准差=0.78）千克/天。逐步回归分析表明，在基础模型中纳入BF和LMA的体重增加量可提高决定系数（R²）（从0.76提高到0.78），并解释了MBW和ADG未解释的DMI变异的9%（RFIp）。剩余采食量和胴体校正剩余采食量（RFIc）与DMI（分别为0.60和0.55）以及饲料转化率（FCR；分别为0.49和0.45）呈中度相关，与生长部分效率（PEG；分别为-0.84和-0.78）呈强相关，但与ADG或MBW无关。BF的增加量与RFIp（0.30）、FCR（-0.15）和PEG（-0.11）呈弱相关，但与RFIc无关。LMA的增加量与RFIp（0.17）和FCR（-0.19）呈弱相关，但与PEG或RFIc无关。RFIp与RFIc之间的斯皮尔曼等级相关性较高（0.91）。采食持续时间（0.41）、低头持续时间（0.38）和采食频率（0.26）与RFIp相关，并解释了MBW、ADG和超声性状未解释的DMI变异的35%（RFIc）。这些结果表明，对胴体组成进行校正后的剩余采食量将有助于在不影响增重速度或组成的情况下，选择降低牛的采食量。
