One hundred and thirty six Angus steers were used to evaluate the effects of feedlot placement weight (PW; weight of the animal at the time of its placement into the feedlot) and days on feed (DOF) on feed efficiency, carcass transfer (CT), and carcass traits. The 2 × 4 factorial experiment included PW (Light (LT), 310 kg BW; or Heavy (HV), 415 kg BW) and DOF (54, 83, 111, or 145 d) before slaughtering. At d 0, four steers selected at random from each PW group were slaughtered to determine initial hot carcass weight (HCW). The rest of the steers were allocated in pens (4 pens/treatment; 4 steers/pen) with ad libitum access to feed and drinking water. No PW × DOF interactions were detected for any response variables (P > 0.05). Heavy steers showed greater (P < 0.001) daily dry matter intake (DMI) than LT steers. Daily DMI did not change (P = 0.11) across DOF. Average daily gain (ADG) and daily carcass weight gain (CWG) were not affected (P > 0.05) by PW. Although ADG showed a quadratic (P = 0.003) response across DOF, CWG was higher (P < 0.05) for steers fed 83 d or longer. This resulted in a linear increase (P < 0.001) in CT (ratio of CWG to ADG, expressed as a percentage) during the 145 feeding period. Feed efficiency (DMI: ADG and DMI: CWG ratios) was better (P < 0.001) for LT than HV steers. The ratio DMI: ADG was higher (P < 0.05) for 145 DOF steers, whereas the ratio DMI: CWG tended (P = 0.08) to be better for 111 DOF. Heavy steers showed greater (P < 0.05) final live weight, HCW, ribeye area, subcutaneous fat thickness, and marbling score than LT steers. Final weight and HCW increased linearly (P < 0.001) with DOF. Subcutaneous fat thickness was higher (P < 0.05) for steers fed 111 d or longer. Marbling score and LM total lipid increased linearly (P < 0.001) with DOF. Longissimus muscle pH and color (a*, b*), and subcutaneous fat color (L*, a*, b*) were not affected (P > 0.05) by treatments. Warner Bratzler shear force did not differ (P = 0.16) between PW but was affected (P = 0.005) by DOF. However, all steaks showed a WBS value below 4.0 kg. Regardless of treatment, WBS decreased (P < 0.001) as postmortem aging days increased. Overall, HV steers produced larger carcasses that had greater fat deposition, and similar tenderness than LT steers. Feeding up to 111 days, regardless PW, could improve animal performance and CT, and produce large carcasses with acceptable levels of subcutaneous fat thickness and palatable beef.

136头安格斯ste牛用于评估饲养场放置重量（PW；将动物放置在饲养场中时的动物体重）和饲喂天数（DOF）对饲料效率，cas体转移（CT）的影响和car体特征。2×4阶乘实验包括屠宰前的PW（轻（LT），310 kg BW；或Heavy（HV），415 kg BW）和DOF（54、83、111或145 d）。在第0天，对从每个PW组中随机选择的四个four牛进行屠宰以确定初始热car体重量（HCW）。其余the牛皮分配为围栏（4支/处理； 4 ers /笔），可随意获取饲料和饮用水。对于任何响应变量，均未检测到PW×DOF相互作用（P > 0.05）。重型装载机表现出更大（P<0.001）的每日干物质摄入量（DMI）高于LT牛。 整个DOF中，每日DMI不变（P = 0.11）。PW不影响平均日增重（ADG）和每日daily体增重（CWG）（P > 0.05）。尽管ADG 在整个DOF上表现出二次响应（P = 0.003），但饲喂83 d或更长时间的ste牛的CWG更高（P <0.05）。这导致在145个饲喂期中CT（CWG与ADG的比率，以百分比表示）线性增加（P <0.001）。LT的饲料效率（DMI：ADG和DMI：CWG比率）比HV ers牛更好（P <0.001）。145 DOF ers牛皮的DMI：ADG比更高（P <0.05），而DMI：CWG的比例则更高（P = 0.08）对于111 DOF更好。重度公牛的最终活重，HCW，肋眼面积，皮下脂肪厚度和大理石花纹得分均比长期公牛高（P <0.05）。最终重量和HCW随着DOF线性增加（P <0.001）。饲喂111 d或更长时间的ste牛皮皮下脂肪厚度更高（P <0.05）。大理石花纹的大理石花纹分数和LM总脂质随DOF线性增加（P <0.001）。纵筋肌的pH值和颜色（a *，b *）和皮下脂肪颜色（L *，a *，b *）不受治疗影响（P > 0.05）。Warner Bratzler的剪切力 在PW之间没有差异（P = 0.16），但受到了影响（P = 0.005）。但是，所有牛排的WBS值均低于4.0千克。无论采用何种治疗方法，随着死后衰老天数的增加，WBS下降（P <0.001）。总体而言，与LT ers牛相比，HV ers牛产生更大的fat体，其脂肪沉积更大，触痛相似。不管PW如何，最多饲养111天都可以改善动物的生长性能和CT，并能生产出具有可接受水平的皮下脂肪厚度和可口牛肉的大型beef体。