This experiment evaluated the effects of advancing days on feed (DOF) on insulin resistance (IR) of finishing Bos indicus bulls offered a high-concentrate diet. On d 0, 100 Bos indicus Nellore bulls were housed in 12 feedlot pens (8 or 9 bulls/pen) for a 108-d feeding period, in a manner that all pens had an equivalent BW at the beginning of the finishing period. Bulls received the same diets throughout the 108-d feeding period. Diets were corn-based (38% starch) and were offered in amounts to ensure ad libitum intake. Individual shrunk BW was obtained on d 0 and 108 after 16 h of feed and water withdrawal, whereas unshrunk BW was recorded on d 19 and 60 for average daily gain (ADG) calculation. From d 0 to 108, feed intake and feed efficiency (FE) were calculated from each pen. Blood samples were collected on d 0, 60, and 108 to assess serum concentrations of haptoglobin, cortisol, glucose, and non-esterified fatty acids (NEFA), and insulin. Glucose, NEFA, and insulin concentrations were used to determine revised quantitative insulin sensitivity check index (RQUICKI), so that lower RQUICKI values indicate a greater IR of the herd. Pen was used as the experimental unit. Overall, DMI increased as DOF also increased (R 2 = 0.71), being greater from d 19 to 60 and 60 to 108 vs. 0 to 19 (P < 0.0001), but did not differ between d 19 to 60 and 60 to 108 (P = 0.79). Conversely, ADG and FE linearly decreased as DOF increased from d 0 to 108 (P < 0.0001; R 2 = 0.68 and 0.79, respectively). Log-transformed RQUICKI decreased as DOF increased up to 108 (P < 0.0001; r = - 0.61). Similarly, serum concentrations of haptoglobin and cortisol increased as RQUICKI increased (P < 0.0001; r = 0.43 and 0.67, respectively). In summary, insulin resistance, per RQUICKI, increased and performance reduced in feedlot bulls with the advance of days on feed. Moreover, inflammatory markers were also positively associated with insulin resistance, suggesting that inflammation might be involved with the incidence of insulin resistance.

中文翻译：

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简短的交流：随着饲养场 Bos indicus 肉牛的饲喂天数的增加，胰岛素抵抗会增加，提供高浓度肥育日粮

本实验评估了提前喂食天数 (DOF) 对提供高浓度日粮的育肥牛胰岛素抵抗 (IR) 的影响。在第 0 天，将 100 头 Bos indicus Nellore 公牛圈养在 12 个饲养场围栏（8 或 9 头公牛/围栏）中，饲养期为 108 天，所有围栏在结束期开始时的 BW 都相同。公牛在整个 108 天的喂养期内接受相同的饮食。饮食以玉米为主（38% 淀粉），并提供一定数量以确保随意摄入。在停食 16 小时后的第 0 天和第 108 天获得个体缩小的体重，而在第 19 天和第 60 天记录未缩小的体重用于平均日增重 (ADG) 计算。从第 0 天到第 108 天，计算每只围栏的采食量和饲料效率 (FE)。在第 0 天、第 60 天采集血样，和 108 评估触珠蛋白、皮质醇、葡萄糖和非酯化脂肪酸 (NEFA) 以及胰岛素的血清浓度。葡萄糖、NEFA 和胰岛素浓度用于确定修正的定量胰岛素敏感性检查指数 (RQUICKI)，因此较低的 RQUICKI 值表明畜群的 IR 较高。笔被用作实验单位。总体而言，DMI 随着 DOF 的增加而增加 (R 2 = 0.71)，从 d 19 到 60 和 60 到 108 对比 0 到 19 (P < 0.0001)，但在 d 19 到 60 和 60 到108 (P = 0.79)。相反，随着 DOF 从 d 0 增加到 108，ADG 和 FE 呈线性下降（分别为 P < 0.0001；R 2 = 0.68 和 0.79）。当 DOF 增加到 108 时，对数转换的 RQUICKI 减少（P < 0.0001；r = - 0.61）。相似地，结合珠蛋白和皮质醇的血清浓度随着 RQUICKI 增加而增加（P < 0.0001；r 分别 = 0.43 和 0.67）。总之，根据 RQUICKI，随着饲喂天数的增加，饲养场公牛的胰岛素抵抗增加而性能降低。此外，炎症标志物也与胰岛素抵抗呈正相关，表明炎症可能与胰岛素抵抗的发生有关。